New language feature: basic error handling. (#2253)

* New language feature: basic error handling.

* Fix.

* Fix `tryCall` encoding according to code review.

Co-authored-by: Yong He <yhe@nvidia.com>

37 files changed, 1205 insertions, 62 deletions

diff --git a/build/visual-studio/slang/slang.vcxproj b/build/visual-studio/slang/slang.vcxproj
index 20bb20565..89e69b55c 100644
--- a/build/visual-studio/slang/slang.vcxproj
+++ b/build/visual-studio/slang/slang.vcxproj
@@ -369,12 +369,14 @@ IF EXIST ..\..\..\external\slang-binaries\bin\windows-aarch64\slang-glslang.dll\
     <ClInclude Include="..\..\..\source\slang\slang-ir-link.h" />

     <ClInclude Include="..\..\..\source\slang\slang-ir-liveness.h" />

     <ClInclude Include="..\..\..\source\slang\slang-ir-lower-bit-cast.h" />

+    <ClInclude Include="..\..\..\source\slang\slang-ir-lower-error-handling.h" />

     <ClInclude Include="..\..\..\source\slang\slang-ir-lower-existential.h" />

     <ClInclude Include="..\..\..\source\slang\slang-ir-lower-generic-call.h" />

     <ClInclude Include="..\..\..\source\slang\slang-ir-lower-generic-function.h" />

     <ClInclude Include="..\..\..\source\slang\slang-ir-lower-generic-type.h" />

     <ClInclude Include="..\..\..\source\slang\slang-ir-lower-generics.h" />

     <ClInclude Include="..\..\..\source\slang\slang-ir-lower-reinterpret.h" />

+    <ClInclude Include="..\..\..\source\slang\slang-ir-lower-result-type.h" />

     <ClInclude Include="..\..\..\source\slang\slang-ir-lower-tuple-types.h" />

     <ClInclude Include="..\..\..\source\slang\slang-ir-metadata.h" />

     <ClInclude Include="..\..\..\source\slang\slang-ir-missing-return.h" />

@@ -511,12 +513,14 @@ IF EXIST ..\..\..\external\slang-binaries\bin\windows-aarch64\slang-glslang.dll\
     <ClCompile Include="..\..\..\source\slang\slang-ir-link.cpp" />

     <ClCompile Include="..\..\..\source\slang\slang-ir-liveness.cpp" />

     <ClCompile Include="..\..\..\source\slang\slang-ir-lower-bit-cast.cpp" />

+    <ClCompile Include="..\..\..\source\slang\slang-ir-lower-error-handling.cpp" />

     <ClCompile Include="..\..\..\source\slang\slang-ir-lower-existential.cpp" />

     <ClCompile Include="..\..\..\source\slang\slang-ir-lower-generic-call.cpp" />

     <ClCompile Include="..\..\..\source\slang\slang-ir-lower-generic-function.cpp" />

     <ClCompile Include="..\..\..\source\slang\slang-ir-lower-generic-type.cpp" />

     <ClCompile Include="..\..\..\source\slang\slang-ir-lower-generics.cpp" />

     <ClCompile Include="..\..\..\source\slang\slang-ir-lower-reinterpret.cpp" />

+    <ClCompile Include="..\..\..\source\slang\slang-ir-lower-result-type.cpp" />

     <ClCompile Include="..\..\..\source\slang\slang-ir-lower-tuple-types.cpp" />

     <ClCompile Include="..\..\..\source\slang\slang-ir-metadata.cpp" />

     <ClCompile Include="..\..\..\source\slang\slang-ir-missing-return.cpp" />

diff --git a/build/visual-studio/slang/slang.vcxproj.filters b/build/visual-studio/slang/slang.vcxproj.filters
index ce66cc2a2..a414d7e6a 100644
--- a/build/visual-studio/slang/slang.vcxproj.filters
+++ b/build/visual-studio/slang/slang.vcxproj.filters
@@ -204,6 +204,9 @@
     <ClInclude Include="..\..\..\source\slang\slang-ir-lower-bit-cast.h">

       <Filter>Header Files</Filter>

     </ClInclude>

+    <ClInclude Include="..\..\..\source\slang\slang-ir-lower-error-handling.h">

+      <Filter>Header Files</Filter>

+    </ClInclude>

     <ClInclude Include="..\..\..\source\slang\slang-ir-lower-existential.h">

       <Filter>Header Files</Filter>

     </ClInclude>

@@ -222,6 +225,9 @@
     <ClInclude Include="..\..\..\source\slang\slang-ir-lower-reinterpret.h">

       <Filter>Header Files</Filter>

     </ClInclude>

+    <ClInclude Include="..\..\..\source\slang\slang-ir-lower-result-type.h">

+      <Filter>Header Files</Filter>

+    </ClInclude>

     <ClInclude Include="..\..\..\source\slang\slang-ir-lower-tuple-types.h">

       <Filter>Header Files</Filter>

     </ClInclude>

@@ -626,6 +632,9 @@
     <ClCompile Include="..\..\..\source\slang\slang-ir-lower-bit-cast.cpp">

       <Filter>Source Files</Filter>

     </ClCompile>

+    <ClCompile Include="..\..\..\source\slang\slang-ir-lower-error-handling.cpp">

+      <Filter>Source Files</Filter>

+    </ClCompile>

     <ClCompile Include="..\..\..\source\slang\slang-ir-lower-existential.cpp">

       <Filter>Source Files</Filter>

     </ClCompile>

@@ -644,6 +653,9 @@
     <ClCompile Include="..\..\..\source\slang\slang-ir-lower-reinterpret.cpp">

       <Filter>Source Files</Filter>

     </ClCompile>

+    <ClCompile Include="..\..\..\source\slang\slang-ir-lower-result-type.cpp">

+      <Filter>Source Files</Filter>

+    </ClCompile>

     <ClCompile Include="..\..\..\source\slang\slang-ir-lower-tuple-types.cpp">

       <Filter>Source Files</Filter>

     </ClCompile>

diff --git a/examples/heterogeneous-hello-world/main.slang b/examples/heterogeneous-hello-world/main.slang
index 2e65c7149..2a9c1eaf1 100644
--- a/examples/heterogeneous-hello-world/main.slang
+++ b/examples/heterogeneous-hello-world/main.slang
@@ -9,20 +9,18 @@ int MessageBoxA(Ptr<void> hwnd, String text, String caption, uint flags);
 [COM]
 interface IObject
 {
-    int getValue(int value);
+    int getValue(int value) throws int;
 }
 
 [DllImport("test-com")]
 IObject createObject();
 
-public __extern_cpp int main()
+public __extern_cpp void main() throws int
 {
     //writeln("hello world");
     //MessageBoxA(nullptr, "hello world!", "example", 0);
 
     IObject object = createObject();
 
-    int rs = object.getValue(2);
-
-    return 0;
+    int rs = try object.getValue(2);
 }
\ No newline at end of file
diff --git a/source/slang/slang-ast-decl.h b/source/slang/slang-ast-decl.h
index 5b596ded0..9c95f3520 100644
--- a/source/slang/slang-ast-decl.h
+++ b/source/slang/slang-ast-decl.h
@@ -266,6 +266,9 @@ class CallableDecl : public ContainerDecl
     }
 
     TypeExp returnType;
+        
+    // If this callable throws an error code, `errorType` is the type of the error code.
+    TypeExp errorType;
 
     // Fields related to redeclaration, so that we
     // can support multiple specialized variations
diff --git a/source/slang/slang-ast-dump.cpp b/source/slang/slang-ast-dump.cpp
index 9da1a0163..d67a35174 100644
--- a/source/slang/slang-ast-dump.cpp
+++ b/source/slang/slang-ast-dump.cpp
@@ -341,7 +341,10 @@ struct ASTDumpContext
     {
         m_writer->emit(getGLSLNameForImageFormat(imageFormat));
     }
-
+    void dump(TryClauseType clauseType)
+    {
+        m_writer->emit(getTryClauseTypeName(clauseType));
+    }
     void dump(const String& string)
     {
         dump(string.getUnownedSlice());
diff --git a/source/slang/slang-ast-expr.h b/source/slang/slang-ast-expr.h
index a6c1d432c..f2fae7ced 100644
--- a/source/slang/slang-ast-expr.h
+++ b/source/slang/slang-ast-expr.h
@@ -144,6 +144,28 @@ class InvokeExpr: public AppExprBase
     SLANG_AST_CLASS(InvokeExpr)
 };
 
+enum class TryClauseType
+{
+    None,
+    Standard, // Normal `try` clause
+    Optional, // (Not implemented) `try?` clause that returns an optional value.
+    Assert, // (Not implemented) `try!` clause that should always succeed and triggers runtime error if failed.
+};
+
+char const* getTryClauseTypeName(TryClauseType value);
+
+class TryExpr : public Expr
+{
+    SLANG_AST_CLASS(TryExpr)
+
+    Expr* base;
+
+    TryClauseType tryClauseType = TryClauseType::Standard;
+
+    // The scope of this expr.
+    Scope* scope = nullptr;
+};
+
 class OperatorExpr: public InvokeExpr
 {
     SLANG_AST_CLASS(OperatorExpr)
diff --git a/source/slang/slang-ast-type.cpp b/source/slang/slang-ast-type.cpp
index b6bc1f170..bcaf8f5a9 100644
--- a/source/slang/slang-ast-type.cpp
+++ b/source/slang/slang-ast-type.cpp
@@ -549,6 +549,11 @@ void FuncType::_toTextOverride(StringBuilder& out)
         out << getParamType(pp);
     }
     out << toSlice(") -> ") << getResultType();
+
+    if (!getErrorType()->equals(getASTBuilder()->getVoidType()))
+    {
+        out << " throws " << getErrorType();
+    }
 }
 
 bool FuncType::_equalsImplOverride(Type * type)
@@ -571,6 +576,9 @@ bool FuncType::_equalsImplOverride(Type * type)
         if (!resultType->equals(funcType->resultType))
             return false;
 
+        if (!errorType->equals(funcType->errorType))
+            return false;
+
         // TODO: if we ever introduce other kinds
         // of qualification on function types, we'd
         // want to consider it here.
@@ -586,6 +594,9 @@ Val* FuncType::_substituteImplOverride(ASTBuilder* astBuilder, SubstitutionSet s
     // result type
     Type* substResultType = as<Type>(resultType->substituteImpl(astBuilder, subst, &diff));
 
+    // error type
+    Type* substErrorType = as<Type>(errorType->substituteImpl(astBuilder, subst, &diff));
+
     // parameter types
     List<Type*> substParamTypes;
     for (auto pp : paramTypes)
@@ -601,6 +612,7 @@ Val* FuncType::_substituteImplOverride(ASTBuilder* astBuilder, SubstitutionSet s
     FuncType* substType = astBuilder->create<FuncType>();
     substType->resultType = substResultType;
     substType->paramTypes = substParamTypes;
+    substType->errorType = substErrorType;
     return substType;
 }
 
@@ -608,6 +620,7 @@ Type* FuncType::_createCanonicalTypeOverride()
 {
     // result type
     Type* canResultType = resultType->getCanonicalType();
+    Type* canErrorType = errorType->getCanonicalType();
 
     // parameter types
     List<Type*> canParamTypes;
@@ -619,7 +632,7 @@ Type* FuncType::_createCanonicalTypeOverride()
     FuncType* canType = getASTBuilder()->create<FuncType>();
     canType->resultType = canResultType;
     canType->paramTypes = canParamTypes;
-
+    canType->errorType = canErrorType;
     return canType;
 }
 
@@ -634,6 +647,7 @@ HashCode FuncType::_getHashCodeOverride()
             hashCode,
             getParamType(pp)->getHashCode());
     }
+    combineHash(hashCode, getErrorType()->getHashCode());
     return hashCode;
 }
 
diff --git a/source/slang/slang-ast-type.h b/source/slang/slang-ast-type.h
index 7aa1a36ab..8de047af5 100644
--- a/source/slang/slang-ast-type.h
+++ b/source/slang/slang-ast-type.h
@@ -575,10 +575,12 @@ class FuncType : public Type
 
     List<Type*> paramTypes;
     Type* resultType = nullptr;
+    Type* errorType = nullptr;
 
     UInt getParamCount() { return paramTypes.getCount(); }
     Type* getParamType(UInt index) { return paramTypes[index]; }
     Type* getResultType() { return resultType; }
+    Type* getErrorType() { return errorType; }
 
     // Overrides should be public so base classes can access
     void _toTextOverride(StringBuilder& out);
diff --git a/source/slang/slang-check-decl.cpp b/source/slang/slang-check-decl.cpp
index 6d579e1fb..af19f484d 100644
--- a/source/slang/slang-check-decl.cpp
+++ b/source/slang/slang-check-decl.cpp
@@ -673,7 +673,7 @@ namespace Slang
     // Make sure a declaration has been checked, so we can refer to it.
     // Note that this may lead to us recursively invoking checking,
     // so this may not be the best way to handle things.
-    void SemanticsVisitor::ensureDecl(Decl* decl, DeclCheckState state)
+    void SemanticsVisitor::ensureDecl(Decl* decl, DeclCheckState state, SemanticsContext* baseContext)
     {
         // If the `decl` has already been checked up to or beyond `state`
         // then there is nothing for us to do.
@@ -733,7 +733,7 @@ namespace Slang
             // context, so that the state at the point where a declaration is *referenced*
             // cannot affect the state in which the declaration is *checked*.
             //
-            SemanticsContext subContext(getShared());
+            SemanticsContext subContext = baseContext ? SemanticsContext(*baseContext) : SemanticsContext(getShared());
             _dispatchDeclCheckingVisitor(decl, nextState, subContext);
 
             // In the common case, the visitor will have done the necessary
@@ -3609,17 +3609,17 @@ namespace Slang
         }
     }
 
-    void SemanticsVisitor::ensureDeclBase(DeclBase* declBase, DeclCheckState state)
+    void SemanticsVisitor::ensureDeclBase(DeclBase* declBase, DeclCheckState state, SemanticsContext* baseContext)
     {
         if(auto decl = as<Decl>(declBase))
         {
-            ensureDecl(decl, state);
+            ensureDecl(decl, state, baseContext);
         }
         else if(auto declGroup = as<DeclGroup>(declBase))
         {
             for(auto dd : declGroup->decls)
             {
-                ensureDecl(dd, state);
+                ensureDecl(dd, state, baseContext);
             }
         }
         else
@@ -4398,6 +4398,17 @@ namespace Slang
         {
             ensureDecl(paramDecl, DeclCheckState::ReadyForReference);
         }
+
+        auto errorType = decl->errorType;
+        if (errorType.exp)
+        {
+            errorType = CheckProperType(errorType);
+        }
+        else
+        {
+            errorType = TypeExp(m_astBuilder->getVoidType());
+        }
+        decl->errorType = errorType;
     }
 
     void SemanticsDeclHeaderVisitor::visitFuncDecl(FuncDecl* funcDecl)
diff --git a/source/slang/slang-check-expr.cpp b/source/slang/slang-check-expr.cpp
index 317ab6a1a..4b29de1bf 100644
--- a/source/slang/slang-check-expr.cpp
+++ b/source/slang/slang-check-expr.cpp
@@ -1337,6 +1337,15 @@ namespace Slang
             // if this is still an invoke expression, test arguments passed to inout/out parameter are LValues
             if(auto funcType = as<FuncType>(invoke->functionExpr->type))
             {
+                if (!funcType->errorType->equals(m_astBuilder->getVoidType()))
+                {
+                    // If the callee throws, make sure we are inside a try clause.
+                    if (m_enclosingTryClauseType == TryClauseType::None)
+                    {
+                        getSink()->diagnose(invoke, Diagnostics::mustUseTryClauseToCallAThrowFunc);
+                    }
+                }
+
                 Index paramCount = funcType->getParamCount();
                 for (Index pp = 0; pp < paramCount; ++pp)
                 {
@@ -1529,6 +1538,59 @@ namespace Slang
         return CheckInvokeExprWithCheckedOperands(expr);
     }
 
+    Expr* SemanticsExprVisitor::visitTryExpr(TryExpr* expr)
+    {
+        auto prevTryClauseType = expr->tryClauseType;
+        m_enclosingTryClauseType = expr->tryClauseType;
+        expr->base = CheckTerm(expr->base);
+        m_enclosingTryClauseType = prevTryClauseType;
+        expr->type = expr->base->type;
+        if (as<ErrorType>(expr->type))
+            return expr;
+        
+        auto parentFunc = this->m_parentFunc;
+        // TODO: check if the try clause is caught.
+        // For now we assume all `try`s are not caught (because we don't have catch yet).
+        if (!parentFunc)
+        {
+            getSink()->diagnose(expr, Diagnostics::uncaughtTryCallInNonThrowFunc);
+            return expr;
+        }
+        if (parentFunc->errorType->equals(m_astBuilder->getVoidType()))
+        {
+            getSink()->diagnose(expr, Diagnostics::uncaughtTryCallInNonThrowFunc);
+            return expr;
+        }
+        if (!as<InvokeExpr>(expr->base))
+        {
+            getSink()->diagnose(expr, Diagnostics::tryClauseMustApplyToInvokeExpr);
+            return expr;
+        }
+        auto base = as<InvokeExpr>(expr->base);
+        if (auto callee = as<DeclRefExpr>(base->functionExpr))
+        {
+            if (auto funcCallee = as<FuncDecl>(callee->declRef.getDecl()))
+            {
+                if (funcCallee->errorType->equals(m_astBuilder->getVoidType()))
+                {
+                    getSink()->diagnose(expr, Diagnostics::tryInvokeCalleeShouldThrow, callee->declRef);
+                }
+                if (!parentFunc->errorType->equals(funcCallee->errorType))
+                {
+                    getSink()->diagnose(
+                        expr,
+                        Diagnostics::errorTypeOfCalleeIncompatibleWithCaller,
+                        callee->declRef,
+                        funcCallee->errorType,
+                        parentFunc->errorType);
+                }
+                return expr;
+            }
+        }
+        getSink()->diagnose(expr, Diagnostics::calleeOfTryCallMustBeFunc);
+        return expr;
+    }
+
     Expr* SemanticsVisitor::MaybeDereference(Expr* inExpr)
     {
         Expr* expr = inExpr;
diff --git a/source/slang/slang-check-impl.h b/source/slang/slang-check-impl.h
index e6088ccca..1e549c7da 100644
--- a/source/slang/slang-check-impl.h
+++ b/source/slang/slang-check-impl.h
@@ -345,6 +345,15 @@ namespace Slang
             return result;
         }
 
+        TryClauseType getEnclosingTryClauseType() { return m_enclosingTryClauseType; }
+
+        SemanticsContext withEnclosingTryClauseType(TryClauseType tryClauseType)
+        {
+            SemanticsContext result(*this);
+            result.m_enclosingTryClauseType = tryClauseType;
+            return result;
+        }
+
             /// A scope that is local to a particular expression, and
             /// that can be used to allocate temporary bindings that
             /// might be needed by that expression or its sub-expressions.
@@ -380,6 +389,7 @@ namespace Slang
 
         ExprLocalScope* m_exprLocalScope = nullptr;
 
+
     protected:
         // TODO: consider making more of this state `private`...
 
@@ -389,6 +399,9 @@ namespace Slang
             /// The linked list of lexically surrounding statements.
         OuterStmtInfo* m_outerStmts = nullptr;
 
+            /// The type of a try clause (if any) enclosing current expr.
+        TryClauseType m_enclosingTryClauseType = TryClauseType::None;
+
         ASTBuilder* m_astBuilder = nullptr;
     };
 
@@ -558,7 +571,7 @@ namespace Slang
             /// on this function to avoid blowing out the stack or (even worse
             /// creating a circular dependency).
             ///
-        void ensureDecl(Decl* decl, DeclCheckState state);
+        void ensureDecl(Decl* decl, DeclCheckState state, SemanticsContext* baseContext = nullptr);
 
             /// Helper routine allowing `ensureDecl` to be called on a `DeclRef`
         void ensureDecl(DeclRefBase const& declRef, DeclCheckState state)
@@ -572,7 +585,7 @@ namespace Slang
             /// called on a `DeclGroup` this function just calls `ensureDecl()`
             /// on each declaration in the group.
             ///
-        void ensureDeclBase(DeclBase* decl, DeclCheckState state);
+        void ensureDeclBase(DeclBase* decl, DeclCheckState state, SemanticsContext* baseContext);
 
         // A "proper" type is one that can be used as the type of an expression.
         // Put simply, it can be a concrete type like `int`, or a generic
@@ -1660,6 +1673,8 @@ namespace Slang
 
         Expr* visitTypeCastExpr(TypeCastExpr * expr);
 
+        Expr* visitTryExpr(TryExpr* expr);
+
         //
         // Some syntax nodes should not occur in the concrete input syntax,
         // and will only appear *after* checking is complete. We need to
diff --git a/source/slang/slang-check-stmt.cpp b/source/slang/slang-check-stmt.cpp
index 45be1d662..57bb3b85a 100644
--- a/source/slang/slang-check-stmt.cpp
+++ b/source/slang/slang-check-stmt.cpp
@@ -51,7 +51,7 @@ namespace Slang
         // local `struct` declaration, where it would have members
         // that need to be recursively checked.
         //
-        ensureDeclBase(stmt->decl, DeclCheckState::Checked);
+        ensureDeclBase(stmt->decl, DeclCheckState::Checked, this);
     }
 
     void SemanticsStmtVisitor::visitBlockStmt(BlockStmt* stmt)
@@ -289,7 +289,7 @@ namespace Slang
     {
         stmt->device = CheckExpr(stmt->device);
         stmt->gridDims = CheckExpr(stmt->gridDims);
-        ensureDeclBase(stmt->dispatchThreadID, DeclCheckState::Checked);
+        ensureDeclBase(stmt->dispatchThreadID, DeclCheckState::Checked, this);
         WithOuterStmt subContext(this, stmt);
         stmt->kernelCall = subContext.CheckExpr(stmt->kernelCall);
         return;
diff --git a/source/slang/slang-diagnostic-defs.h b/source/slang/slang-diagnostic-defs.h
index 57035e84e..9ab34128a 100644
--- a/source/slang/slang-diagnostic-defs.h
+++ b/source/slang/slang-diagnostic-defs.h
@@ -290,6 +290,13 @@ DIAGNOSTIC(33071, Error, expectedAStringLiteral, "expected a string literal")
 DIAGNOSTIC(   -1, Note, noteExplicitConversionPossible, "explicit conversion from '$0' to '$1' is possible")
 DIAGNOSTIC(30080, Error, ambiguousConversion, "more than one implicit conversion exists from '$0' to '$1'")
 
+DIAGNOSTIC(30090, Error, tryClauseMustApplyToInvokeExpr, "expression in a 'try' clause must be a call to a function or operator overload.")
+DIAGNOSTIC(30091, Error, tryInvokeCalleeShouldThrow, "'$0' called from a 'try' clause does not throw an error, make sure the callee is marked as 'throws'")
+DIAGNOSTIC(30092, Error, calleeOfTryCallMustBeFunc, "callee in a 'try' clause must be a function")
+DIAGNOSTIC(30093, Error, uncaughtTryCallInNonThrowFunc, "the current function or environment is not declared to throw any errors, but the 'try' clause is not caught")
+DIAGNOSTIC(30094, Error, mustUseTryClauseToCallAThrowFunc, "the callee may throw an error, and therefore must be called within a 'try' clause")
+DIAGNOSTIC(30095, Error, errorTypeOfCalleeIncompatibleWithCaller, "the error type `$1` of callee `$0` is not compatible with the caller's error type `$2`.")
+
 // Attributes
 DIAGNOSTIC(31000, Error, unknownAttributeName, "unknown attribute '$0'")
 DIAGNOSTIC(31001, Error, attributeArgumentCountMismatch, "attribute '$0' expects $1 arguments ($2 provided)")
diff --git a/source/slang/slang-emit.cpp b/source/slang/slang-emit.cpp
index 0ed17ad7c..72ad80873 100644
--- a/source/slang/slang-emit.cpp
+++ b/source/slang/slang-emit.cpp
@@ -23,6 +23,7 @@
 #include "slang-ir-com-interface.h"
 #include "slang-ir-lower-generics.h"
 #include "slang-ir-lower-tuple-types.h"
+#include "slang-ir-lower-result-type.h"
 #include "slang-ir-lower-bit-cast.h"
 #include "slang-ir-lower-reinterpret.h"
 #include "slang-ir-metadata.h"
@@ -200,6 +201,19 @@ Result linkAndOptimizeIR(
     // un-specialized IR.
     dumpIRIfEnabled(codeGenContext, irModule);
 
+    switch (target)
+    {
+    default:
+        break;
+    case CodeGenTarget::HostCPPSource:
+        lowerComInterfaces(irModule, sink);
+        generateDllImportFuncs(irModule, sink);
+        break;
+    }
+
+    // Lower `Result<T,E>` types into ordinary struct types.
+    lowerResultType(irModule, sink);
+
     // Replace any global constants with their values.
     //
     replaceGlobalConstants(irModule);
@@ -689,16 +703,6 @@ Result linkAndOptimizeIR(
         break;
     }
 
-    switch (target)
-    {
-    default:
-        break;
-    case CodeGenTarget::HostCPPSource:
-        lowerComInterfaces(irModule, sink);
-        generateDllImportFuncs(irModule, sink);
-        break;
-    }
-
     // TODO: our current dynamic dispatch pass will remove all uses of witness tables.
     // If we are going to support function-pointer based, "real" modular dynamic dispatch,
     // we will need to disable this pass.
diff --git a/source/slang/slang-ir-deduplicate.cpp b/source/slang/slang-ir-deduplicate.cpp
index f2c199af6..8aef7736c 100644
--- a/source/slang/slang-ir-deduplicate.cpp
+++ b/source/slang/slang-ir-deduplicate.cpp
@@ -76,4 +76,37 @@ namespace Slang
         for (auto inst : instToRemove)
             inst->removeAndDeallocate();
     }
+
+    void SharedIRBuilder::replaceGlobalInst(IRInst* oldInst, IRInst* newInst)
+    {
+        List<IRUse*> uses;
+        for (auto use = oldInst->firstUse; use; use = use->nextUse)
+        {
+            uses.add(use);
+        }
+
+        bool shouldUpdateGlobalNumberedCache = false;
+        for (auto use : uses)
+        {
+            use->set(newInst);
+            // depending on the type of the user inst, we may need to rebuild and update the global
+            // numbering cache.
+            if (isGloballyNumberedInst(use->getUser()))
+            {
+                shouldUpdateGlobalNumberedCache = true;
+            }
+        }
+        oldInst->removeAndDeallocate();
+        if (shouldUpdateGlobalNumberedCache)
+        {
+            deduplicateAndRebuildGlobalNumberingMap();
+        }
+    }
+
+    bool SharedIRBuilder::isGloballyNumberedInst(IRInst* inst)
+    {
+        if (!inst->getParent() || inst->getParent()->getOp() != kIROp_Module)
+            return false;
+        return m_globalValueNumberingMap.ContainsKey(IRInstKey{inst});
+    }
 }
diff --git a/source/slang/slang-ir-generics-lowering-context.cpp b/source/slang/slang-ir-generics-lowering-context.cpp
index 284e1fa11..bf3b8d855 100644
--- a/source/slang/slang-ir-generics-lowering-context.cpp
+++ b/source/slang/slang-ir-generics-lowering-context.cpp
@@ -36,6 +36,12 @@ namespace Slang
         return false;
     }
 
+    bool isComInterfaceType(IRType* type)
+    {
+        return type->findDecoration<IRComInterfaceDecoration>() != nullptr ||
+               type->getOp() == kIROp_ComPtrType;
+    }
+
     bool isTypeValue(IRInst* typeInst)
     {
         if (typeInst)
@@ -175,7 +181,7 @@ namespace Slang
             if (isBuiltin(interfaceType))
                 return (IRType*)paramType;
 
-            if (interfaceType->findDecoration<IRComInterfaceDecoration>())
+            if (isComInterfaceType((IRType*)interfaceType))
                 return (IRType*)interfaceType;
 
             auto anyValueSize = getInterfaceAnyValueSize(
@@ -192,7 +198,7 @@ namespace Slang
             if (isBuiltin(paramType))
                 return (IRType*)paramType;
 
-            if (paramType->findDecoration<IRComInterfaceDecoration>())
+            if (isComInterfaceType((IRType*)paramType))
                 return (IRType*)paramType;
 
             // In the dynamic-dispatch case, a value of interface type
diff --git a/source/slang/slang-ir-generics-lowering-context.h b/source/slang/slang-ir-generics-lowering-context.h
index 23bdcc78b..475464c8f 100644
--- a/source/slang/slang-ir-generics-lowering-context.h
+++ b/source/slang/slang-ir-generics-lowering-context.h
@@ -99,6 +99,8 @@ namespace Slang
 
     bool isPolymorphicType(IRInst* typeInst);
 
+    bool isComInterfaceType(IRType* type);
+
     // Returns true if typeInst represents a type and should be lowered into
     // Ptr(RTTIType).
     bool isTypeValue(IRInst* typeInst);
diff --git a/source/slang/slang-ir-inst-defs.h b/source/slang/slang-ir-inst-defs.h
index c617a0218..b1759026b 100644
--- a/source/slang/slang-ir-inst-defs.h
+++ b/source/slang/slang-ir-inst-defs.h
@@ -56,6 +56,7 @@ INST(Nop, nop, 0, 0)
 
     INST(ConjunctionType, Conjunction, 0, 0)
     INST(AttributedType, Attributed, 0, 0)
+    INST(ResultType, Result, 2, 0)
 
     /* BindExistentialsTypeBase */
 
@@ -274,6 +275,12 @@ INST(makeArray, makeArray, 0, 0)
 INST(makeStruct, makeStruct, 0, 0)
 INST(MakeTuple, makeTuple, 0, 0)
 INST(GetTupleElement, getTupleElement, 2, 0)
+INST(MakeResultValue, makeResultValue, 1, 0)
+INST(MakeResultValueVoid, makeResultValueVoid, 0, 0)
+INST(MakeResultError, makeResultError, 1, 0)
+INST(IsResultError, isResultError, 1, 0)
+INST(GetResultError, getResultError, 1, 0)
+INST(GetResultValue, getResultValue, 1, 0)
 
 INST(Call, call, 1, 0)
 
@@ -435,6 +442,9 @@ INST(SwizzledStore, swizzledStore, 2, 0)
         INST(ifElse, ifElse, 4, 0)
     INST_RANGE(ConditionalBranch, conditionalBranch, ifElse)
 
+    INST(Throw, throw, 1, 0)
+    // tryCall <successBlock> <failBlock> <callee> <args>...
+    INST(TryCall, tryCall, 3, 0)
     // switch <val> <break> <default> <caseVal1> <caseBlock1> ...
     INST(Switch, switch, 3, 0)
 
@@ -730,7 +740,8 @@ INST_RANGE(Layout, VarLayout, EntryPointLayout)
         INST(TypeSizeAttr, size, 2, 0)
         INST(VarOffsetAttr, offset, 2, 0)
     INST_RANGE(LayoutResourceInfoAttr, TypeSizeAttr, VarOffsetAttr)
-INST_RANGE(Attr, PendingLayoutAttr, VarOffsetAttr)
+    INST(FuncThrowTypeAttr, FuncThrowType, 1, 0)
+INST_RANGE(Attr, PendingLayoutAttr, FuncThrowTypeAttr)
 
 /* Liveness */
     INST(LiveRangeStart, liveRangeStart, 2, 0)
diff --git a/source/slang/slang-ir-insts.h b/source/slang/slang-ir-insts.h
index 77b3eabc0..f7f7328a1 100644
--- a/source/slang/slang-ir-insts.h
+++ b/source/slang/slang-ir-insts.h
@@ -689,6 +689,14 @@ struct IRVarOffsetAttr : public IRLayoutResourceInfoAttr
     }
 };
 
+    /// An attribute that specifies the error type a function is throwing
+struct IRFuncThrowTypeAttr : IRAttr
+{
+    IR_LEAF_ISA(FuncThrowTypeAttr)
+
+    IRType* getErrorType() { return (IRType*)getOperand(0); }
+};
+
     /// An attribute that specifies size information for a single resource kind.
 struct IRTypeSizeAttr : public IRLayoutResourceInfoAttr
 {
@@ -1547,6 +1555,25 @@ struct IRSwitch : IRTerminatorInst
     IRBlock* getCaseLabel(UInt index) { return (IRBlock*) getOperand(3 + index*2 + 1); }
 };
 
+struct IRThrow : IRTerminatorInst
+{
+    IR_LEAF_ISA(Throw);
+
+    IRInst* getValue() { return getOperand(0); }
+};
+
+struct IRTryCall : IRTerminatorInst
+{
+    IR_LEAF_ISA(TryCall);
+
+    IRBlock* getSuccessBlock() { return cast<IRBlock>(getOperand(0)); }
+    IRBlock* getFailureBlock() { return cast<IRBlock>(getOperand(1)); }
+    IRInst* getCallee() { return getOperand(2); }
+    UInt getArgCount() { return getOperandCount() - 3; }
+    IRUse* getArgs() { return getOperands() + 3; }
+    IRInst* getArg(UInt index) { return getOperand(index + 3); }
+};
+
 struct IRSwizzle : IRInst
 {
     IRUse base;
@@ -1758,6 +1785,52 @@ struct IRGetTupleElement : IRInst
     IRInst* getElementIndex() { return getOperand(1); }
 };
 
+// Constructs an `Result<T,E>` value from an error code.
+struct IRMakeResultError : IRInst
+{
+    IR_LEAF_ISA(MakeResultError)
+
+    IRInst* getErrorValue() { return getOperand(0); }
+};
+
+// Constructs an `Result<T,E>` value from an valid value.
+struct IRMakeResultValue : IRInst
+{
+    IR_LEAF_ISA(MakeResultValue)
+
+    IRInst* getValue() { return getOperand(0); }
+};
+
+// Constructs an `Result<void,E>` value that represents success in a function that returns `void`.
+struct IRMakeResultValueVoid : IRInst
+{
+    IR_LEAF_ISA(MakeResultValueVoid)
+};
+
+// Determines if a `Result` value represents an error.
+struct IRIsResultError : IRInst
+{
+    IR_LEAF_ISA(IsResultError)
+
+    IRInst* getResultOperand() { return getOperand(0); }
+};
+
+// Extract the value from a `Result`.
+struct IRGetResultValue : IRInst
+{
+    IR_LEAF_ISA(GetResultValue)
+
+    IRInst* getResultOperand() { return getOperand(0); }
+};
+
+// Extract the error code from a `Result`.
+struct IRGetResultError : IRInst
+{
+    IR_LEAF_ISA(GetResultError)
+
+    IRInst* getResultOperand() { return getOperand(0); }
+};
+
     /// An instruction that packs a concrete value into an existential-type "box"
 struct IRMakeExistential : IRInst
 {
@@ -1908,12 +1981,17 @@ public:
     // keys are modified (thus its hash code is changed).
     void deduplicateAndRebuildGlobalNumberingMap();
 
+    // Replaces all uses of oldInst with newInst, and ensures the global numbering map is valid after the replacement.
+    void replaceGlobalInst(IRInst* oldInst, IRInst* newInst);
+
     typedef Dictionary<IRInstKey, IRInst*> GlobalValueNumberingMap;
     typedef Dictionary<IRConstantKey, IRConstant*> ConstantMap;
 
     GlobalValueNumberingMap& getGlobalValueNumberingMap() { return m_globalValueNumberingMap; }
     ConstantMap& getConstantMap() { return m_constantMap; }
 
+    bool isGloballyNumberedInst(IRInst* inst);
+
 private:
     // The module that will own all of the IR
     IRModule* m_module;
@@ -2104,6 +2182,8 @@ public:
     IRTupleType* getTupleType(IRType* type0, IRType* type1, IRType* type2);
     IRTupleType* getTupleType(IRType* type0, IRType* type1, IRType* type2, IRType* type3);
 
+    IRResultType* getResultType(IRType* valueType, IRType* errorType);
+
     IRBasicBlockType*   getBasicBlockType();
     IRWitnessTableType* getWitnessTableType(IRType* baseType);
     IRWitnessTableIDType* getWitnessTableIDType(IRType* baseType);
@@ -2152,6 +2232,9 @@ public:
         IRType*         resultType);
 
     IRFuncType* getFuncType(
+        UInt paramCount, IRType* const* paramTypes, IRType* resultType, IRAttr* attribute);
+
+    IRFuncType* getFuncType(
         List<IRType*> const&    paramTypes,
         IRType*                 resultType)
     {
@@ -2279,6 +2362,14 @@ public:
         return emitCallInst(type, func, args.getCount(), args.getBuffer());
     }
 
+    IRInst* emitTryCallInst(
+        IRType* type,
+        IRBlock* successBlock,
+        IRBlock* failureBlock,
+        IRInst* func,
+        UInt argCount,
+        IRInst* const* args);
+
     IRInst* createIntrinsicInst(
         IRType*         type,
         IROp            op,
@@ -2322,6 +2413,13 @@ public:
 
     IRInst* emitGetTupleElement(IRType* type, IRInst* tuple, UInt element);
 
+    IRInst* emitMakeResultError(IRType* resultType, IRInst* errorVal);
+    IRInst* emitMakeResultValue(IRType* resultType, IRInst* val);
+    IRInst* emitMakeResultValueVoid(IRType* resultType);
+    IRInst* emitIsResultError(IRInst* result);
+    IRInst* emitGetResultError(IRInst* result);
+    IRInst* emitGetResultValue(IRInst* result);
+
     IRInst* emitMakeVector(
         IRType*         type,
         UInt            argCount,
@@ -2590,6 +2688,8 @@ public:
 
     IRInst* emitReturn();
 
+    IRInst* emitThrow(IRInst* val);
+
     IRInst* emitDiscard();
 
     IRInst* emitUnreachable();
@@ -2687,6 +2787,8 @@ public:
 
     IRInst* emitAdd(IRType* type, IRInst* left, IRInst* right);
     IRInst* emitMul(IRType* type, IRInst* left, IRInst* right);
+    IRInst* emitEql(IRInst* left, IRInst* right);
+    IRInst* emitNeq(IRInst* left, IRInst* right);
     IRInst* emitShr(IRType* type, IRInst* op0, IRInst* op1);
     IRInst* emitShl(IRType* type, IRInst* op0, IRInst* op1);
 
diff --git a/source/slang/slang-ir-lower-error-handling.cpp b/source/slang/slang-ir-lower-error-handling.cpp
new file mode 100644
index 000000000..5a1389e57
--- /dev/null
+++ b/source/slang/slang-ir-lower-error-handling.cpp
@@ -0,0 +1,242 @@
+// slang-ir-lower-error-handling.cpp
+
+#include "slang-ir-lower-error-handling.h"
+
+#include "slang-ir.h"
+#include "slang-ir-insts.h"
+
+namespace Slang
+{
+
+struct ErrorHandlingLoweringContext
+{
+    IRModule* module;
+    DiagnosticSink* diagnosticSink;
+
+    SharedIRBuilder sharedBuilder;
+
+    List<IRInst*> workList;
+    HashSet<IRInst*> workListSet;
+
+    void addToWorkList(IRInst* inst)
+    {
+        if (workListSet.Contains(inst))
+            return;
+
+        workList.add(inst);
+        workListSet.Add(inst);
+    }
+
+    void processFuncType(IRFuncType* funcType)
+    {
+        auto throwAttr = funcType->findAttr<IRFuncThrowTypeAttr>();
+        if (!throwAttr)
+            return;
+        IRBuilder builder(sharedBuilder);
+        builder.setInsertBefore(funcType);
+        auto resultType =
+            builder.getResultType(funcType->getResultType(), throwAttr->getErrorType());
+        List<IRType*> paramTypes;
+        for (UInt i = 0; i < funcType->getParamCount(); i++)
+        {
+            if (as<IRAttr>(funcType->getParamType(i)))
+                break;
+            paramTypes.add(funcType->getParamType(i));
+        }
+        auto newFuncType = builder.getFuncType(paramTypes, resultType);
+        sharedBuilder.replaceGlobalInst(funcType, newFuncType);
+    }
+
+    void processTryCall(IRTryCall* tryCall)
+    {
+        // If we see:
+        // ```
+        //      value = tryCall(callee, successBlock, failBlock, args)
+        //  successBlock:
+        //      resultParam = IRParam<resultType>
+        //      ... (uses resultParam) ...
+        //  failBlock:
+        //      errorParam = IRParam<errorType>
+        //      (uses errorParam)
+        // ```
+        // We need to rewrite it as
+        // ```
+        //      result = call(callee) : Result<callee.returnType, callee.errorType>
+        //      isError = isResultError(result)
+        //      ifElse(isError, failBlock, successBlock)
+        //  successBlock:
+        //      value = getResultValue(result) : returnType
+        //      ... (replaces resultParam with value)
+        //  failBlock:
+        //      error = getResultError(result) : errorType
+        //      ... (replaces errorParam with error)
+        // ```
+        IRFuncType* funcType = cast<IRFuncType>(tryCall->getCallee()->getDataType());
+        auto resultValueType = funcType->getResultType();
+        auto throwAttr = funcType->findAttr<IRFuncThrowTypeAttr>();
+        if (!throwAttr)
+        {
+            SLANG_ASSERT_FAILURE("tryCall applied to callee without a IRFuncThrowTypeAttr");
+        }
+        auto errorType = throwAttr->getErrorType();
+
+        IRBuilder builder(sharedBuilder);
+        builder.setInsertBefore(tryCall);
+
+        auto resultType = builder.getResultType(resultValueType, errorType);
+        List<IRInst*> args;
+        for (UInt i = 0; i < tryCall->getArgCount(); i++)
+        {
+            args.add(tryCall->getArg(i));
+        }
+        auto call = builder.emitCallInst(resultType, tryCall->getCallee(), args);
+        auto isFail = builder.emitIsResultError(call);
+        auto failBlock = tryCall->getFailureBlock();
+        auto successBlock = tryCall->getSuccessBlock();
+
+        builder.emitIf(isFail, failBlock, successBlock);
+
+        // Replace the params in failBlock to `getResultError(call)`.
+        builder.setInsertBefore(failBlock->getFirstOrdinaryInst());
+        auto errorParam = failBlock->getFirstParam();
+        auto errVal = builder.emitGetResultError(call);
+        errorParam->replaceUsesWith(errVal);
+        errorParam->removeAndDeallocate();
+
+        // Replace the params in successBlock to `getResultValue(call)`.
+        builder.setInsertBefore(successBlock->getFirstOrdinaryInst());
+        auto resultParam = successBlock->getFirstParam();
+        auto resultValue = builder.emitGetResultValue(call);
+        resultParam->replaceUsesWith(resultValue);
+        resultParam->removeAndDeallocate();
+
+        tryCall->removeAndDeallocate();
+    }
+
+    void processReturn(IRReturn* ret)
+    {
+        auto parentFunc = getParentFunc(ret);
+        if (!parentFunc)
+            return;
+        auto funcType = cast<IRFuncType>(parentFunc->getDataType());
+        auto throwAttr = funcType->findAttr<IRFuncThrowTypeAttr>();
+        if (!throwAttr)
+            return;
+
+        // If we are in a throwing function and sees a `return(val)` inst,
+        // replace it with a `return makeResultValue(val)`, so that it returns a `Result<T,E>` type.
+        IRBuilder builder(sharedBuilder);
+        builder.setInsertBefore(ret);
+        auto resultType =
+            builder.getResultType(funcType->getResultType(), throwAttr->getErrorType());
+        IRInst* resultVal = nullptr;
+        if (ret->getOp() == kIROp_ReturnVal)
+        {
+            auto val = cast<IRReturnVal>(ret)->getVal();
+            resultVal = builder.emitMakeResultValue(resultType, val);
+        }
+        else
+        {
+            resultVal = builder.emitMakeResultValueVoid(resultType);
+        }
+        builder.emitReturn(resultVal);
+        ret->removeAndDeallocate();
+    }
+
+    void processThrow(IRThrow* throwInst)
+    {
+        auto parentFunc = getParentFunc(throwInst);
+        SLANG_ASSERT(parentFunc);
+        auto funcType = cast<IRFuncType>(parentFunc->getDataType());
+        auto throwAttr = funcType->findAttr<IRFuncThrowTypeAttr>();
+        SLANG_ASSERT(throwAttr);
+
+        // If we are in a throwing function and sees a `throw(e)` inst,
+        // replace it with a `return makeResultError(e)`.
+        IRBuilder builder(sharedBuilder);
+        builder.setInsertBefore(throwInst);
+        auto resultType =
+            builder.getResultType(funcType->getResultType(), throwAttr->getErrorType());
+        IRInst* resultVal = builder.emitMakeResultError(resultType, throwInst->getValue());
+        builder.emitReturn(resultVal);
+        throwInst->removeAndDeallocate();
+    }
+
+    void processInst(IRInst* inst)
+    {
+        switch (inst->getOp())
+        {
+        case kIROp_TryCall:
+            processTryCall(cast<IRTryCall>(inst));
+            break;
+        case kIROp_ReturnVal:
+        case kIROp_ReturnVoid:
+            processReturn(cast<IRReturn>(inst));
+            break;
+        case kIROp_Throw:
+            processThrow(cast<IRThrow>(inst));
+            break;
+        default:
+            break;
+        }
+    }
+
+    void processInsts()
+    {
+        addToWorkList(module->getModuleInst());
+
+        while (workList.getCount() != 0)
+        {
+            IRInst* inst = workList.getLast();
+
+            workList.removeLast();
+            workListSet.Remove(inst);
+
+            processInst(inst);
+
+            for (auto child = inst->getLastChild(); child; child = child->getPrevInst())
+            {
+                addToWorkList(child);
+            }
+        }
+    }
+
+    void processModule()
+    {
+        // Deduplicate equivalent types.
+        sharedBuilder.deduplicateAndRebuildGlobalNumberingMap();   
+
+        // Translate all IRTryCall, IRThrow, IRReturn, IRReturnVal.
+        processInsts();
+
+        // Lower all functypes.
+        // Function types with an IRThrowTypeAttribute will be translated into a normal function
+        // type that returns `Result<T,E>`.
+        List<IRFuncType*> oldFuncTypes;
+        for (auto child : module->getGlobalInsts())
+        {
+            switch (child->getOp())
+            {
+            case kIROp_FuncType:
+                oldFuncTypes.add(cast<IRFuncType>(child));
+                break;
+            default:
+                break;
+            }
+        }
+        for (auto funcType : oldFuncTypes)
+        {
+            processFuncType(funcType);
+        }
+    }
+};
+
+void lowerErrorHandling(IRModule* module, DiagnosticSink* sink)
+{
+    ErrorHandlingLoweringContext context;
+    context.module = module;
+    context.diagnosticSink = sink;
+    context.sharedBuilder.init(module);
+    return context.processModule();
+}
+}
diff --git a/source/slang/slang-ir-lower-error-handling.h b/source/slang/slang-ir-lower-error-handling.h
new file mode 100644
index 000000000..92a65404c
--- /dev/null
+++ b/source/slang/slang-ir-lower-error-handling.h
@@ -0,0 +1,18 @@
+// slang-ir-lower-error-handling.h
+#pragma once
+
+namespace Slang
+{
+
+struct IRModule;
+class DiagnosticSink;
+
+/// Lower error handling related opcodes and function calls to use standard control flow.
+/// A function with an error code type will be translated into a function that returns `Result<T,E>`, which can be
+/// further lowered to standard return values and `out` parameters in a separate pass.
+/// Call sites (`IRTryCall`) to error-throwing function will be rewritten to conform to the new function signature.
+/// `IRThrow` will be replaced with `IRReturnVal(IRMakeErrorResult(e))`.
+/// 
+void lowerErrorHandling(IRModule* module, DiagnosticSink* sink);
+
+}
diff --git a/source/slang/slang-ir-lower-existential.cpp b/source/slang/slang-ir-lower-existential.cpp
index dfa714a82..b0d9e6f2f 100644
--- a/source/slang/slang-ir-lower-existential.cpp
+++ b/source/slang/slang-ir-lower-existential.cpp
@@ -106,7 +106,7 @@ namespace Slang
             builder->setInsertBefore(extractInst);
 
             IRInst* element = nullptr;
-            if (extractInst->getOperand(0)->getDataType()->findDecoration<IRComInterfaceDecoration>())
+            if (isComInterfaceType(extractInst->getOperand(0)->getDataType()))
             {
                 // If this is an COM interface, the elements (witness table/rtti) are just the interface value itself.
                 element = extractInst->getOperand(0);
diff --git a/source/slang/slang-ir-lower-generic-call.cpp b/source/slang/slang-ir-lower-generic-call.cpp
index da9f54764..7dbe11f52 100644
--- a/source/slang/slang-ir-lower-generic-call.cpp
+++ b/source/slang/slang-ir-lower-generic-call.cpp
@@ -276,9 +276,7 @@ namespace Slang
             // all occurences of associatedtypes.
 
             // If `w` in `lookup_interface_method(w, ...)` is a COM interface, bail.
-            if (lookupInst->getWitnessTable()
-                    ->getDataType()
-                    ->findDecoration<IRComInterfaceDecoration>())
+            if (isComInterfaceType(lookupInst->getWitnessTable()->getDataType()))
             {
                 return;
             }
diff --git a/source/slang/slang-ir-lower-generic-function.cpp b/source/slang/slang-ir-lower-generic-function.cpp
index 600f21b20..a2636e8ed 100644
--- a/source/slang/slang-ir-lower-generic-function.cpp
+++ b/source/slang/slang-ir-lower-generic-function.cpp
@@ -153,7 +153,7 @@ namespace Slang
             if (isBuiltin(interfaceType))
                 return interfaceType;
             // Do not lower COM interfaces.
-            if (interfaceType->findDecoration<IRComInterfaceDecoration>())
+            if (isComInterfaceType(interfaceType))
                 return interfaceType;
 
             List<IRInterfaceRequirementEntry*> newEntries;
diff --git a/source/slang/slang-ir-lower-generics.cpp b/source/slang/slang-ir-lower-generics.cpp
index 5d8e6d929..703441252 100644
--- a/source/slang/slang-ir-lower-generics.cpp
+++ b/source/slang/slang-ir-lower-generics.cpp
@@ -137,7 +137,7 @@ namespace Slang
                 {
                     auto witnessTableType = lookupWitnessMethod->getWitnessTable()->getDataType();
                     auto interfaceType = cast<IRWitnessTableType>(witnessTableType)->getConformanceType();
-                    if (interfaceType->findDecoration<IRComInterfaceDecoration>())
+                    if (isComInterfaceType((IRType*)interfaceType))
                         return;
                     if (!implementedInterfaces.Contains(interfaceType))
                     {
diff --git a/source/slang/slang-ir-lower-result-type.cpp b/source/slang/slang-ir-lower-result-type.cpp
new file mode 100644
index 000000000..e46a0ceb5
--- /dev/null
+++ b/source/slang/slang-ir-lower-result-type.cpp
@@ -0,0 +1,317 @@
+// slang-ir-lower-result-type.cpp
+
+#include "slang-ir-lower-result-type.h"
+#include "slang-ir.h"
+#include "slang-ir-insts.h"
+
+namespace Slang
+{
+    struct ResultTypeLoweringContext
+    {
+        IRModule* module;
+        DiagnosticSink* sink;
+
+        SharedIRBuilder sharedBuilderStorage;
+
+        List<IRInst*> workList;
+        HashSet<IRInst*> workListSet;
+
+        struct LoweredResultTypeInfo : public RefObject
+        {
+            IRType* resultType = nullptr;
+            IRType* errorType = nullptr;
+            IRType* valueType = nullptr;
+            IRType* loweredType = nullptr;
+            IRStructField* valueField = nullptr;
+            IRStructField* errorField = nullptr;
+        };
+        Dictionary<IRInst*, RefPtr<LoweredResultTypeInfo>> mapLoweredTypeToResultTypeInfo;
+        Dictionary<IRInst*, RefPtr<LoweredResultTypeInfo>> loweredResultTypes;
+
+        IRType* maybeLowerResultType(IRBuilder* builder, IRType* type)
+        {
+            if (auto info = getLoweredResultType(builder, type))
+                return info->loweredType;
+            else
+                return type;
+        }
+
+        LoweredResultTypeInfo* getLoweredResultType(IRBuilder* builder, IRInst* type)
+        {
+            if (auto loweredInfo = loweredResultTypes.TryGetValue(type))
+                return loweredInfo->Ptr();
+            if (auto loweredInfo = mapLoweredTypeToResultTypeInfo.TryGetValue(type))
+                return loweredInfo->Ptr();
+
+            if (!type)
+                return nullptr;
+            if (type->getOp() != kIROp_ResultType)
+                return nullptr;
+
+            RefPtr<LoweredResultTypeInfo> info = new LoweredResultTypeInfo();
+            info->resultType = (IRType*)type;
+            info->errorType = cast<IRResultType>(type)->getErrorType();
+            
+            auto resultType = cast<IRResultType>(type);
+            auto valueType = resultType->getValueType();
+            if (valueType->getOp() != kIROp_VoidType)
+            {
+                auto structType = builder->createStructType();
+                info->loweredType = structType;
+                builder->addNameHintDecoration(structType, UnownedStringSlice("ResultType"));
+
+                info->valueType = valueType;
+                auto valueKey = builder->createStructKey();
+                builder->addNameHintDecoration(valueKey, UnownedStringSlice("value"));
+                info->valueField = builder->createStructField(structType, valueKey, (IRType*)valueType);
+
+                auto errorType = resultType->getErrorType();
+                auto errorKey = builder->createStructKey();
+                builder->addNameHintDecoration(errorKey, UnownedStringSlice("error"));
+                info->errorField = builder->createStructField(structType, errorKey, (IRType*)errorType);
+            }
+            else
+            {
+                info->loweredType = resultType->getErrorType();
+            }
+            mapLoweredTypeToResultTypeInfo[info->loweredType] = info;
+            loweredResultTypes[type] = info;
+            return info.Ptr();
+        }
+
+        void addToWorkList(
+            IRInst* inst)
+        {
+            for (auto ii = inst->getParent(); ii; ii = ii->getParent())
+            {
+                if (as<IRGeneric>(ii))
+                    return;
+            }
+
+            if (workListSet.Contains(inst))
+                return;
+
+            workList.add(inst);
+            workListSet.Add(inst);
+        }
+
+        IRInst* getSuccessErrorValue(IRType* type)
+        {
+            switch (type->getOp())
+            {
+            case kIROp_Int8Type:
+            case kIROp_Int16Type:
+            case kIROp_IntType:
+            case kIROp_Int64Type:
+            case kIROp_UInt8Type:
+            case kIROp_UInt16Type:
+            case kIROp_UIntType:
+            case kIROp_UInt64Type:
+                break;
+            default:
+                SLANG_ASSERT_FAILURE("error type is not lowered to an integer type.");
+            }
+            IRBuilder builderStorage(sharedBuilderStorage);
+            auto builder = &builderStorage;
+            builder->setInsertInto(module);
+            return builder->getIntValue(type, 0);
+        }
+
+        void processMakeResultValue(IRMakeResultValue* inst)
+        {
+            IRBuilder builderStorage(sharedBuilderStorage);
+            auto builder = &builderStorage;
+            builder->setInsertBefore(inst);
+
+            auto info = getLoweredResultType(builder, inst->getDataType());
+            List<IRInst*> operands;
+            operands.add(inst->getOperand(0));
+            operands.add(getSuccessErrorValue(info->errorType));
+            auto makeStruct = builder->emitMakeStruct(info->loweredType, operands);
+            inst->replaceUsesWith(makeStruct);
+            inst->removeAndDeallocate();
+        }
+
+        void processMakeResultValueVoid(IRMakeResultValueVoid* inst)
+        {
+            IRBuilder builderStorage(sharedBuilderStorage);
+            auto builder = &builderStorage;
+            builder->setInsertBefore(inst);
+
+            auto info = getLoweredResultType(builder, inst->getDataType());
+            auto errCode = getSuccessErrorValue(info->errorType);
+            inst->replaceUsesWith(errCode);
+            inst->removeAndDeallocate();
+        }
+
+        void processMakeResultError(IRMakeResultError* inst)
+        {
+            IRBuilder builderStorage(sharedBuilderStorage);
+            auto builder = &builderStorage;
+            builder->setInsertBefore(inst);
+
+            auto info = getLoweredResultType(builder, inst->getDataType());
+            if (info->valueField)
+            {
+                List<IRInst*> operands;
+                operands.add(builder->emitConstructorInst(info->valueType, 0, nullptr));
+                operands.add(inst->getErrorValue());
+                auto makeStruct = builder->emitMakeStruct(info->loweredType, operands);
+                inst->replaceUsesWith(makeStruct);
+            }
+            else
+            {
+                inst->replaceUsesWith(inst->getErrorValue());
+            }
+            inst->removeAndDeallocate();
+        }
+
+        IRInst* getResultError(IRBuilder* builder, IRInst* resultInst)
+        {
+            auto loweredResultTypeInfo = getLoweredResultType(builder, resultInst->getDataType());
+            SLANG_ASSERT(loweredResultTypeInfo);
+            if (loweredResultTypeInfo->valueField)
+            {
+                auto value = builder->emitFieldExtract(
+                    loweredResultTypeInfo->errorType,
+                    resultInst,
+                    loweredResultTypeInfo->errorField->getKey());
+                return value;
+            }
+            else
+            {
+                return resultInst;
+            }
+        }
+
+        void processGetResultError(IRGetResultError* inst)
+        {
+            IRBuilder builderStorage(sharedBuilderStorage);
+            auto builder = &builderStorage;
+            builder->setInsertBefore(inst);
+
+            auto resultValue = inst->getResultOperand();
+            auto errValue = getResultError(builder, resultValue);
+            inst->replaceUsesWith(errValue);
+            inst->removeAndDeallocate();
+        }
+
+        void processGetResultValue(IRGetResultValue* inst)
+        {
+            IRBuilder builderStorage(sharedBuilderStorage);
+            auto builder = &builderStorage;
+            builder->setInsertBefore(inst);
+
+            auto base = inst->getResultOperand();
+            auto loweredResultTypeInfo = getLoweredResultType(builder, base->getDataType());
+            SLANG_ASSERT(loweredResultTypeInfo);
+            SLANG_ASSERT(loweredResultTypeInfo->valueField);
+            auto getElement = builder->emitFieldExtract(
+                loweredResultTypeInfo->errorType,
+                base,
+                loweredResultTypeInfo->valueField->getKey());
+            inst->replaceUsesWith(getElement);
+            inst->removeAndDeallocate();
+        }
+
+        void processIsResultError(IRIsResultError* inst)
+        {
+            IRBuilder builderStorage(sharedBuilderStorage);
+            auto builder = &builderStorage;
+            builder->setInsertBefore(inst);
+
+            auto base = inst->getResultOperand();
+            auto loweredResultTypeInfo = getLoweredResultType(builder, base->getDataType());
+            SLANG_ASSERT(loweredResultTypeInfo);
+            SLANG_ASSERT(loweredResultTypeInfo->valueField);
+
+            auto resultValue = inst->getResultOperand();
+            auto errValue = getResultError(builder, resultValue);
+            auto isSuccess =
+                builder->emitNeq(errValue, getSuccessErrorValue(loweredResultTypeInfo->errorType));
+            inst->replaceUsesWith(isSuccess);
+            inst->removeAndDeallocate();
+        }
+
+        void processResultType(IRResultType* inst)
+        {
+            IRBuilder builderStorage(sharedBuilderStorage);
+            auto builder = &builderStorage;
+            builder->setInsertBefore(inst);
+
+            auto loweredResultTypeInfo = getLoweredResultType(builder, inst);
+            SLANG_ASSERT(loweredResultTypeInfo);
+            SLANG_UNUSED(loweredResultTypeInfo);
+        }
+
+        void processInst(IRInst* inst)
+        {
+            switch (inst->getOp())
+            {
+            case kIROp_MakeResultValue:
+                processMakeResultValue((IRMakeResultValue*)inst);
+                break;
+            case kIROp_MakeResultValueVoid:
+                processMakeResultValueVoid((IRMakeResultValueVoid*)inst);
+                break;
+            case kIROp_MakeResultError:
+                processMakeResultError((IRMakeResultError*)inst);
+                break;
+            case kIROp_GetResultError:
+                processGetResultError((IRGetResultError*)inst);
+                break;
+            case kIROp_GetResultValue:
+                processGetResultValue((IRGetResultValue*)inst);
+                break;
+            case kIROp_IsResultError:
+                processIsResultError((IRIsResultError*)inst);
+                break;
+            case kIROp_ResultType:
+                processResultType((IRResultType*)inst);
+                break;
+            default:
+                break;
+            }
+        }
+
+        void processModule()
+        {
+            SharedIRBuilder* sharedBuilder = &sharedBuilderStorage;
+            sharedBuilder->init(module);
+
+            // Deduplicate equivalent types.
+            sharedBuilder->deduplicateAndRebuildGlobalNumberingMap();
+
+            addToWorkList(module->getModuleInst());
+
+            while (workList.getCount() != 0)
+            {
+                IRInst* inst = workList.getLast();
+
+                workList.removeLast();
+                workListSet.Remove(inst);
+
+                processInst(inst);
+
+                for (auto child = inst->getLastChild(); child; child = child->getPrevInst())
+                {
+                    addToWorkList(child);
+                }
+            }
+
+            // Replace all result types with lowered struct types.
+            for (auto kv : loweredResultTypes)
+            {
+                kv.Key->replaceUsesWith(kv.Value->loweredType);
+            }
+        }
+    };
+    
+    void lowerResultType(IRModule* module, DiagnosticSink* sink)
+    {
+        ResultTypeLoweringContext context;
+        context.module = module;
+        context.sink = sink;
+        context.processModule();
+    }
+}
diff --git a/source/slang/slang-ir-lower-result-type.h b/source/slang/slang-ir-lower-result-type.h
new file mode 100644
index 000000000..f04a1a6cb
--- /dev/null
+++ b/source/slang/slang-ir-lower-result-type.h
@@ -0,0 +1,16 @@
+// slang-ir-lower-result-type.h
+#pragma once
+
+#include "slang-ir.h"
+
+namespace Slang
+{
+    struct IRModule;
+    class DiagnosticSink;
+
+    /// Lower `IRResultType<T,E>` types to ordinary `struct`s.
+    void lowerResultType(
+        IRModule* module,
+        DiagnosticSink* sink);
+
+}
diff --git a/source/slang/slang-ir-specialize-dynamic-associatedtype-lookup.cpp b/source/slang/slang-ir-specialize-dynamic-associatedtype-lookup.cpp
index 6c6a7dec5..7464a1c35 100644
--- a/source/slang/slang-ir-specialize-dynamic-associatedtype-lookup.cpp
+++ b/source/slang/slang-ir-specialize-dynamic-associatedtype-lookup.cpp
@@ -119,7 +119,7 @@ struct AssociatedTypeLookupSpecializationContext
 
     void processLookupInterfaceMethodInst(IRLookupWitnessMethod* inst)
     {
-        if (inst->getWitnessTable()->getDataType()->findDecoration<IRComInterfaceDecoration>())
+        if (isComInterfaceType(inst->getWitnessTable()->getDataType()))
         {
             return;
         }
diff --git a/source/slang/slang-ir-witness-table-wrapper.cpp b/source/slang/slang-ir-witness-table-wrapper.cpp
index c8a1e2dbe..5d1a9360e 100644
--- a/source/slang/slang-ir-witness-table-wrapper.cpp
+++ b/source/slang/slang-ir-witness-table-wrapper.cpp
@@ -170,7 +170,7 @@ namespace Slang
             auto interfaceType = cast<IRInterfaceType>(witnessTable->getConformanceType());
             if (isBuiltin(interfaceType))
                 return;
-            if (interfaceType->findDecoration<IRComInterfaceDecoration>())
+            if (isComInterfaceType(interfaceType))
                 return;
 
             // We need to consider whether the concrete type that is conforming
diff --git a/source/slang/slang-ir.cpp b/source/slang/slang-ir.cpp
index d454333e6..c71954346 100644
--- a/source/slang/slang-ir.cpp
+++ b/source/slang/slang-ir.cpp
@@ -2587,6 +2587,12 @@ namespace Slang
         return getTupleType(SLANG_COUNT_OF(operands), operands);
     }
 
+    IRResultType* IRBuilder::getResultType(IRType* valueType, IRType* errorType)
+    {
+        IRInst* operands[] = {valueType, errorType};
+        return (IRResultType*)getType(kIROp_ResultType, 2, operands);
+    }
+
     IRBasicBlockType*   IRBuilder::getBasicBlockType()
     {
         return (IRBasicBlockType*)getType(kIROp_BasicBlockType);
@@ -2717,6 +2723,14 @@ namespace Slang
             (IRInst* const*) paramTypes);
     }
 
+    IRFuncType* IRBuilder::getFuncType(
+        UInt paramCount, IRType* const* paramTypes, IRType* resultType, IRAttr* attribute)
+    {
+        UInt counts[3] = {1, paramCount, 1};
+        IRInst** lists[3] = {(IRInst**)&resultType, (IRInst**)paramTypes, (IRInst**)&attribute};
+        return (IRFuncType*)findOrEmitHoistableInst(nullptr, kIROp_FuncType, 3, counts, lists);
+    }
+
     IRWitnessTableType* IRBuilder::getWitnessTableType(
         IRType* baseType)
     {
@@ -3088,6 +3102,21 @@ namespace Slang
         return inst;
     }
 
+    IRInst* IRBuilder::emitTryCallInst(
+        IRType* type,
+        IRBlock* successBlock,
+        IRBlock* failureBlock,
+        IRInst* func,
+        UInt argCount,
+        IRInst* const* args)
+    {
+        IRInst* fixedArgs[] = {successBlock, failureBlock, func};
+        auto inst = createInstWithTrailingArgs<IRTryCall>(
+            this, kIROp_TryCall, type, 3, fixedArgs, argCount, args);
+        addInst(inst);
+        return inst;
+    }
+
     IRInst* IRBuilder::createIntrinsicInst(
         IRType*         type,
         IROp            op,
@@ -3183,6 +3212,46 @@ namespace Slang
         return emitIntrinsicInst(type, kIROp_GetTupleElement, 2, args);
     }
 
+    IRInst* IRBuilder::emitMakeResultError(IRType* resultType, IRInst* errorVal)
+    {
+        return emitIntrinsicInst(resultType, kIROp_MakeResultError, 1, &errorVal);
+    }
+
+    IRInst* IRBuilder::emitMakeResultValue(IRType* resultType, IRInst* value)
+    {
+        return emitIntrinsicInst(resultType, kIROp_MakeResultValue, 1, &value);
+    }
+
+    IRInst* IRBuilder::emitMakeResultValueVoid(IRType* resultType)
+    {
+        return emitIntrinsicInst(resultType, kIROp_MakeResultValueVoid, 0, nullptr);
+    }
+
+    IRInst* IRBuilder::emitIsResultError(IRInst* result)
+    {
+        return emitIntrinsicInst(getBoolType(), kIROp_IsResultError, 1, &result);
+    }
+
+    IRInst* IRBuilder::emitGetResultError(IRInst* result)
+    {
+        SLANG_ASSERT(result->getDataType());
+        return emitIntrinsicInst(
+            cast<IRResultType>(result->getDataType())->getErrorType(),
+            kIROp_GetResultError,
+            1,
+            &result);
+    }
+
+    IRInst* IRBuilder::emitGetResultValue(IRInst* result)
+    {
+        SLANG_ASSERT(result->getDataType());
+        return emitIntrinsicInst(
+            cast<IRResultType>(result->getDataType())->getValueType(),
+            kIROp_GetResultValue,
+            1,
+            &result);
+    }
+
     IRInst* IRBuilder::emitMakeVector(
         IRType*         type,
         UInt            argCount,
@@ -3880,6 +3949,13 @@ namespace Slang
         return inst;
     }
 
+    IRInst* IRBuilder::emitThrow(IRInst* val)
+    {
+        auto inst = createInst<IRThrow>(this, kIROp_Throw, nullptr, val);
+        addInst(inst);
+        return inst;
+    }
+
     IRInst* IRBuilder::emitUnreachable()
     {
         auto inst = createInst<IRUnreachable>(
@@ -4207,6 +4283,20 @@ namespace Slang
         return inst;
     }
 
+    IRInst* IRBuilder::emitEql(IRInst* left, IRInst* right)
+    {
+        auto inst = createInst<IRInst>(this, kIROp_Eql, getBoolType(), left, right);
+        addInst(inst);
+        return inst;
+    }
+
+    IRInst* IRBuilder::emitNeq(IRInst* left, IRInst* right)
+    {
+        auto inst = createInst<IRInst>(this, kIROp_Neq, getBoolType(), left, right);
+        addInst(inst);
+        return inst;
+    }
+
     IRInst* IRBuilder::emitMul(IRType* type, IRInst* left, IRInst* right)
     {
         auto inst = createInst<IRInst>(
diff --git a/source/slang/slang-ir.h b/source/slang/slang-ir.h
index 6c766542f..6593e4409 100644
--- a/source/slang/slang-ir.h
+++ b/source/slang/slang-ir.h
@@ -1458,6 +1458,15 @@ struct IRTupleType : IRType
     IR_LEAF_ISA(TupleType)
 };
 
+/// Represents an `Result<T,E>`, used by functions that throws error codes.
+struct IRResultType : IRType
+{
+    IR_LEAF_ISA(ResultType)
+
+    IRType* getValueType() { return (IRType*)getOperand(0); }
+    IRType* getErrorType() { return (IRType*)getOperand(1); }
+};
+
 struct IRTypeType : IRType
 {
     IR_LEAF_ISA(TypeType);
diff --git a/source/slang/slang-lower-to-ir.cpp b/source/slang/slang-lower-to-ir.cpp
index 5cfb07c1c..1448139fb 100644
--- a/source/slang/slang-lower-to-ir.cpp
+++ b/source/slang/slang-lower-to-ir.cpp
@@ -16,6 +16,7 @@
 #include "slang-ir-validate.h"
 #include "slang-ir-string-hash.h"
 #include "slang-ir-clone.h"
+#include "slang-ir-lower-error-handling.h"
 
 #include "slang-mangle.h"
 #include "slang-type-layout.h"
@@ -612,6 +613,12 @@ int32_t getIntrinsicOp(
     return int32_t(irOp);
 }
 
+struct TryClauseEnvironment
+{
+    TryClauseType clauseType = TryClauseType::None;
+    IRBlock* catchBlock = nullptr;
+};
+
 // Given a `LoweredValInfo` for something callable, along with a
 // bunch of arguments, emit an appropriate call to it.
 LoweredValInfo emitCallToVal(
@@ -619,7 +626,8 @@ LoweredValInfo emitCallToVal(
     IRType*         type,
     LoweredValInfo  funcVal,
     UInt            argCount,
-    IRInst* const* args)
+    IRInst* const*  args,
+    const TryClauseEnvironment& tryEnv)
 {
     auto builder = context->irBuilder;
     switch (funcVal.flavor)
@@ -627,8 +635,33 @@ LoweredValInfo emitCallToVal(
     case LoweredValInfo::Flavor::None:
         SLANG_UNEXPECTED("null function");
     default:
-        return LoweredValInfo::simple(
-            builder->emitCallInst(type, getSimpleVal(context, funcVal), argCount, args));
+        switch (tryEnv.clauseType)
+        {
+        case TryClauseType::None:
+            return LoweredValInfo::simple(
+                builder->emitCallInst(type, getSimpleVal(context, funcVal), argCount, args));
+
+        case TryClauseType::Standard:
+            {
+                auto callee = getSimpleVal(context, funcVal);
+                auto succBlock = builder->createBlock();
+                auto failBlock = builder->createBlock();
+                auto funcType = as<IRFuncType>(callee->getDataType());
+                auto throwAttr = funcType->findAttr<IRFuncThrowTypeAttr>();
+                assert(throwAttr);
+                auto voidType = builder->getVoidType();
+                builder->emitTryCallInst(voidType, succBlock, failBlock, callee, argCount, args);
+                builder->insertBlock(failBlock);
+                auto errParam = builder->emitParam(throwAttr->getErrorType());
+                builder->emitThrow(errParam);
+                builder->insertBlock(succBlock);
+                auto value = builder->emitParam(type);
+                return LoweredValInfo::simple(value);
+            }
+            break;
+        default:
+            SLANG_UNIMPLEMENTED_X("emitCallToVal(tryClauseType)");
+        }
     }
 }
 
@@ -655,7 +688,8 @@ LoweredValInfo emitCallToDeclRef(
     DeclRef<Decl>   funcDeclRef,
     IRType*         funcType,
     UInt            argCount,
-    IRInst* const* args)
+    IRInst* const*  args,
+    const TryClauseEnvironment& tryEnv)
 {
     SLANG_ASSERT(funcType);
 
@@ -700,7 +734,7 @@ LoweredValInfo emitCallToDeclRef(
     // Fallback case is to emit an actual call.
     //
     LoweredValInfo funcVal = emitDeclRef(context, funcDeclRef, funcType);
-    return emitCallToVal(context, type, funcVal, argCount, args);
+    return emitCallToVal(context, type, funcVal, argCount, args, tryEnv);
 }
 
 LoweredValInfo emitCallToDeclRef(
@@ -708,9 +742,17 @@ LoweredValInfo emitCallToDeclRef(
     IRType*                 type,
     DeclRef<Decl>           funcDeclRef,
     IRType*                 funcType,
-    List<IRInst*> const&    args)
+    List<IRInst*> const&    args,
+    const TryClauseEnvironment& tryEnv)
 {
-    return emitCallToDeclRef(context, type, funcDeclRef, funcType, args.getCount(), args.getBuffer());
+    return emitCallToDeclRef(
+        context,
+        type,
+        funcDeclRef,
+        funcType,
+        args.getCount(),
+        args.getBuffer(),
+        tryEnv);
 }
 
     /// Represents the "direction" that a parameter is being passed (e.g., `in` or `out`
@@ -1580,10 +1622,21 @@ struct ValLoweringVisitor : ValVisitor<ValLoweringVisitor, LoweredValInfo, Lower
         {
             paramTypes.add(lowerType(context, type->getParamType(pp)));
         }
-        return getBuilder()->getFuncType(
-            paramCount,
-            paramTypes.getBuffer(),
-            resultType);
+        if (type->errorType->equals(context->astBuilder->getVoidType()))
+        {
+            return getBuilder()->getFuncType(
+                paramCount,
+                paramTypes.getBuffer(),
+                resultType);
+        }
+        else
+        {
+            auto errorType = lowerType(context, type->getErrorType());
+            auto irThrowFuncTypeAttribute =
+                getBuilder()->getAttr(kIROp_FuncThrowTypeAttr, 1, (IRInst**)&errorType);
+            return getBuilder()->getFuncType(
+                paramCount, paramTypes.getBuffer(), resultType, irThrowFuncTypeAttribute);
+        }
     }
 
     IRType* visitPtrType(PtrType* type)
@@ -2784,11 +2837,20 @@ void _lowerFuncDeclBaseTypeInfo(
         // being accessed, rather than a simple value.
         irResultType = builder->getPtrType(irResultType);
     }
-
-    outInfo.type = builder->getFuncType(
-        paramTypes.getCount(),
-        paramTypes.getBuffer(),
-        irResultType);
+  
+    auto errorType = lowerType(context, getErrorCodeType(context->astBuilder, declRef));
+    if (errorType->getOp() != kIROp_VoidType)
+    {
+        IRAttr* throwTypeAttr = nullptr;
+        throwTypeAttr = builder->getAttr(kIROp_FuncThrowTypeAttr, 1, (IRInst**)&errorType);
+        outInfo.type = builder->getFuncType(
+            paramTypes.getCount(), paramTypes.getBuffer(), irResultType, throwTypeAttr);
+    }
+    else
+    {
+        outInfo.type =
+            builder->getFuncType(paramTypes.getCount(), paramTypes.getBuffer(), irResultType);
+    }
 }
 
 static LoweredValInfo _emitCallToAccessor(
@@ -2824,7 +2886,8 @@ static LoweredValInfo _emitCallToAccessor(
         accessorDeclRef,
         info.type,
         allArgs.getCount(),
-        allArgs.getBuffer());
+        allArgs.getBuffer(),
+        TryClauseEnvironment());
 
     applyOutArgumentFixups(context, fixups);
 
@@ -3524,6 +3587,11 @@ struct ExprLoweringVisitorBase : ExprVisitor<Derived, LoweredValInfo>
 
     LoweredValInfo visitInvokeExpr(InvokeExpr* expr)
     {
+        return visitInvokeExprImpl(expr, TryClauseEnvironment());
+    }
+
+    LoweredValInfo visitInvokeExprImpl(InvokeExpr* expr, const TryClauseEnvironment& tryEnv)
+    {
         auto type = lowerType(context, expr->type);
 
         // We are going to look at the syntactic form of
@@ -3636,7 +3704,8 @@ struct ExprLoweringVisitorBase : ExprVisitor<Derived, LoweredValInfo>
                 type,
                 funcDeclRef,
                 funcType,
-                irArgs);
+                irArgs,
+                tryEnv);
             applyOutArgumentFixups(context, argFixups);
             return result;
         }
@@ -3658,6 +3727,16 @@ struct ExprLoweringVisitorBase : ExprVisitor<Derived, LoweredValInfo>
         UNREACHABLE_RETURN(LoweredValInfo());
     }
 
+        /// Emit code for a `try` invoke.
+    LoweredValInfo visitTryExpr(TryExpr* expr)
+    {
+        auto invokeExpr = as<InvokeExpr>(expr->base);
+        assert(invokeExpr);
+        TryClauseEnvironment tryEnv;
+        tryEnv.clauseType = expr->tryClauseType;
+        return visitInvokeExprImpl(invokeExpr, tryEnv);
+    }
+
         /// Emit code to cast `value` to a concrete `superType` (e.g., a `struct`).
         ///
         /// The `subTypeWitness` is expected to witness the sub-type relationship
@@ -8338,7 +8417,13 @@ RefPtr<IRModule> generateIRForTranslationUnit(
 
     //      dumpIR(module);
 
-    // First, inline calls to any functions that have been
+    // First, lower error handling logic into normal control flow.
+    // This includes lowering throwing functions into functions that
+    // returns a `Result<T,E>` value, translating `tryCall` into
+    // normal `call` + `ifElse`, etc.
+    lowerErrorHandling(module, compileRequest->getSink());
+
+    // Next, inline calls to any functions that have been
     // marked for mandatory "early" inlining.
     //
     performMandatoryEarlyInlining(module);
diff --git a/source/slang/slang-parser.cpp b/source/slang/slang-parser.cpp
index db532a601..2604ffd9b 100644
--- a/source/slang/slang-parser.cpp
+++ b/source/slang/slang-parser.cpp
@@ -1485,6 +1485,12 @@ namespace Slang
             parser->PushScope(decl);
 
             parseParameterList(parser, decl);
+
+            if (AdvanceIf(parser, "throws"))
+            {
+                decl->errorType = parser->ParseTypeExp();
+            }
+
             _parseOptSemantics(parser, decl);
             decl->body = parseOptBody(parser);
 
@@ -3383,6 +3389,10 @@ namespace Slang
         {
             parser->PushScope(decl);
             parseModernParamList(parser, decl);
+            if (AdvanceIf(parser, "throws"))
+            {
+                decl->errorType = parser->ParseTypeExp();
+            }
             if(AdvanceIf(parser, TokenType::RightArrow))
             {
                 decl->returnType = parser->ParseTypeExp();
@@ -4860,6 +4870,15 @@ namespace Slang
         return parser->astBuilder->create<NullPtrLiteralExpr>();
     }
 
+    static NodeBase* parseTryExpr(Parser* parser, void* /*userData*/)
+    {
+        auto tryExpr = parser->astBuilder->create<TryExpr>();
+        tryExpr->tryClauseType = TryClauseType::Standard;
+        tryExpr->base = parser->ParseLeafExpression();
+        tryExpr->scope = parser->currentScope;
+        return tryExpr;
+    }
+
     static bool _isFinite(double value)
     {
         // Lets type pun double to uint64_t, so we can detect special double values
@@ -6263,7 +6282,7 @@ namespace Slang
         // keyword (no further tokens expected/allowed),
         // and which can be represented just by creating
         // a new AST node of the corresponding type.
-
+        
         _makeParseModifier("in",            InModifier::kReflectClassInfo),
         _makeParseModifier("input",         InputModifier::kReflectClassInfo),
         _makeParseModifier("out",           OutModifier::kReflectClassInfo),
@@ -6336,6 +6355,7 @@ namespace Slang
         _makeParseExpr("true",  parseTrueExpr),
         _makeParseExpr("false", parseFalseExpr),
         _makeParseExpr("nullptr", parseNullPtrExpr),
+        _makeParseExpr("try",     parseTryExpr),
         _makeParseExpr("__TaggedUnion", parseTaggedUnionType),
     };
 
diff --git a/source/slang/slang-serialize-type-info.h b/source/slang/slang-serialize-type-info.h
index 7ed45bb0b..c80eb8051 100644
--- a/source/slang/slang-serialize-type-info.h
+++ b/source/slang/slang-serialize-type-info.h
@@ -142,6 +142,12 @@ struct SerialTypeInfo<bool>
     }
 };
 
+// Specialization for all enum types
+template<typename T>
+struct SerialTypeInfo<T, typename std::enable_if<std::is_enum<T>::value>::type>
+    : public SerialIdentityTypeInfo<T>
+{};
+
 // Pointer
 // Could handle different pointer base types with some more template magic here, but instead went with Pointer type to keep
 // things simpler.
diff --git a/source/slang/slang-serialize.h b/source/slang/slang-serialize.h
index 990a36adc..fcd2daa1f 100644
--- a/source/slang/slang-serialize.h
+++ b/source/slang/slang-serialize.h
@@ -37,7 +37,7 @@ struct SerialClass;
 struct SerialField;
 
 // Type used to implement mechanisms to convert to and from serial types.
-template <typename T>
+template <typename T, typename /*enumTypeSFINAE*/ = void>
 struct SerialTypeInfo;
 
 enum class SerialTypeKind : uint8_t
diff --git a/source/slang/slang-syntax.cpp b/source/slang/slang-syntax.cpp
index b9a5b8cd5..24ccfa4a4 100644
--- a/source/slang/slang-syntax.cpp
+++ b/source/slang/slang-syntax.cpp
@@ -1057,6 +1057,7 @@ Index getFilterCountImpl(const ReflectClassInfo& clsInfo, MemberFilterStyle filt
         FuncType* funcType = astBuilder->create<FuncType>();
 
         funcType->resultType = getResultType(astBuilder, declRef);
+        funcType->errorType = getErrorCodeType(astBuilder, declRef);
         for (auto paramDeclRef : getParameters(declRef))
         {
             auto paramDecl = paramDeclRef.getDecl();
@@ -1269,9 +1270,27 @@ char const* getGLSLNameForImageFormat(ImageFormat format)
     return kImageFormatInfos[Index(format)].name.begin();
 }
 
- const ImageFormatInfo& getImageFormatInfo(ImageFormat format)
- {
-     return kImageFormatInfos[Index(format)];
- }
+
+const ImageFormatInfo& getImageFormatInfo(ImageFormat format)
+{
+    return kImageFormatInfos[Index(format)];
+}
+
+char const* getTryClauseTypeName(TryClauseType c)
+{
+    switch (c)
+    {
+    case TryClauseType::None:
+        return "None";
+    case TryClauseType::Standard:
+        return "Standard";
+    case TryClauseType::Optional:
+        return "Optional";
+    case TryClauseType::Assert:
+        return "Assert";
+    default:
+        return "Unknown";
+    }
+}
 
 } // namespace Slang
diff --git a/source/slang/slang-syntax.h b/source/slang/slang-syntax.h
index c144ceb70..b4463a77d 100644
--- a/source/slang/slang-syntax.h
+++ b/source/slang/slang-syntax.h
@@ -162,6 +162,18 @@ namespace Slang
         return declRef.substitute(astBuilder, declRef.getDecl()->returnType.type);
     }
 
+    inline Type* getErrorCodeType(ASTBuilder* astBuilder, DeclRef<CallableDecl> const& declRef)
+    {
+        if (declRef.getDecl()->errorType.type)
+        {
+            return declRef.substitute(astBuilder, declRef.getDecl()->errorType.type);
+        }
+        else
+        {
+            return astBuilder->getVoidType();
+        }
+    }
+
     inline FilteredMemberRefList<ParamDecl> getParameters(DeclRef<CallableDecl> const& declRef)
     {
         return getMembersOfType<ParamDecl>(declRef);