Support generic interface methods (#251)

* improve diagnostic messages and prevent fatal errors from crashing the compiler.

* fix top level exception catching.

* spelling fix

* change wording of invalidSwizzleExpr diagnostic

* add speculative GenericsApp expr parsing

* add new test case of cascading generics call.

* Fixing bugs in compiling cascaded generic function calls.

Add implementation of DeclaredSubTypeWitness::SubstituteImpl()

This is not needed by the type checker, but needed by IR specialization. When input source contains cascading generic function call, the arguments to `specialize` instruction is currently represented as a substitution. The arg values of this subsittution can be a `DeclaredSubTypeWitness` when a generic function uses one of its generic parameter to specialize another generic function. When the top level generics function is being specialized, this substitution argument, which is a `DeclaredSubTypeWitness`, needs to be substituted with the witness that used to specialize the top level function in the specialized specialize instruction as well.

* add a test case for cascading generic function call.

* parser bug fix

* fixes #255

* add test case for issue #255

* Generate missing `specialize` instruction when calling a generic method from an interface constraint.

When calling a generic method via an interface, we should be generating the following ir:
...
f = lookup_interface_method(...)
f_s = specailize(f, declRef)
...

This commit fixes this  `emitFuncRef` function to emit the needed `specialize` instruction.

* fixes #260

This fix follows the second apporach in the disucssion. It generated mangled name for specialized functions by appending new substitution type names to the original mangled name.

* Disabling removing and re-inserting specailized functions in getSpecalizeFunc()

I am not sure why it is needed, it seems HLSL and GLSL backends are generating forward declarations anyways, so the order of functions in IRModule shouldn't matter.

* cleanup and complete test cases.

* fix warnings

1 files changed, 31 insertions, 3 deletions

diff --git a/source/slang/lower-to-ir.cpp b/source/slang/lower-to-ir.cpp
index 2c64c539b..4fabd6a81 100644
--- a/source/slang/lower-to-ir.cpp
+++ b/source/slang/lower-to-ir.cpp
@@ -314,6 +314,13 @@ LoweredValInfo emitDeclRef(
     IRGenContext*   context,
     DeclRef<Decl>   declRef);
 
+// Emit necessary `specialize` instruction needed by a declRef.
+// This is currently used by emitDeclRef() and emitFuncRef()
+LoweredValInfo maybeEmitSpecializeInst(IRGenContext*   context, 
+    LoweredValInfo loweredDecl,  // the lowered value of the inner decl
+    DeclRef<Decl>   declRef      // the full decl ref containing substitutions
+);
+
 
 IRValue* getSimpleVal(IRGenContext* context, LoweredValInfo lowered);
 
@@ -488,10 +495,11 @@ LoweredValInfo emitFuncRef(
 
                 RefPtr<Type> type = funcExpr->type;
 
-                return LoweredValInfo::simple(context->irBuilder->emitLookupInterfaceMethodInst(
+                auto loweredVal = LoweredValInfo::simple(context->irBuilder->emitLookupInterfaceMethodInst(
                     type,
                     baseMemberDeclRef,
                     funcDeclRef));
+                return maybeEmitSpecializeInst(context, loweredVal, funcDeclRef);
             }
         }
     }
@@ -2893,6 +2901,13 @@ struct DeclLoweringVisitor : DeclVisitor<DeclLoweringVisitor, LoweredValInfo>
         return LoweredValInfo::simple(irFunc);
     }
 
+    LoweredValInfo visitGenericDecl(GenericDecl * genDecl)
+    {
+        if (auto innerFuncDecl = genDecl->inner->As<FuncDecl>())
+            return lowerFuncDecl(innerFuncDecl);
+        SLANG_RELEASE_ASSERT(false);
+        UNREACHABLE_RETURN(LoweredValInfo());
+    }
 
     LoweredValInfo visitFunctionDeclBase(FunctionDeclBase* decl)
     {
@@ -2997,6 +3012,11 @@ RefPtr<Val> lowerSubstitutionArg(
     }
     else if (auto declaredSubtypeWitness = dynamic_cast<DeclaredSubtypeWitness*>(val))
     {
+        // We do not have a concrete witness table yet for a GenericTypeConstraintDecl witness
+
+        if (declaredSubtypeWitness->declRef.As<GenericTypeConstraintDecl>())
+            return val;
+
         // We need to look up the IR-level representation of the witness
         // (which is a witness table).
 
@@ -3073,9 +3093,16 @@ LoweredValInfo emitDeclRef(
     // unspecialized declaration.
     LoweredValInfo loweredDecl = ensureDecl(context, declRef.getDecl());
 
+    return maybeEmitSpecializeInst(context, loweredDecl, declRef);
+}
+
+LoweredValInfo maybeEmitSpecializeInst(IRGenContext*   context,
+    LoweredValInfo loweredDecl,
+    DeclRef<Decl>   declRef)
+{
     // If this declaration reference doesn't involve any specializations,
     // then we are done at this point.
-    if(!hasGenericSubstitutions(declRef.substitutions))
+    if (!hasGenericSubstitutions(declRef.substitutions))
         return loweredDecl;
 
     auto val = getSimpleVal(context, loweredDecl);
@@ -3089,7 +3116,7 @@ LoweredValInfo emitDeclRef(
 
 
     RefPtr<Type> type;
-    if(auto declType = val->getType())
+    if (auto declType = val->getType())
     {
         type = declType->Substitute(declRef.substitutions).As<Type>();
     }
@@ -3102,6 +3129,7 @@ LoweredValInfo emitDeclRef(
         declRef));
 }
 
+
 static void lowerEntryPointToIR(
     IRGenContext*       context,
     EntryPointRequest*  entryPointRequest)