Allow `static const` interface requirements. (#2378)

9 files changed, 238 insertions, 38 deletions

diff --git a/source/slang/slang-ast-decl.cpp b/source/slang/slang-ast-decl.cpp
index edc79c030..2df9164fb 100644
--- a/source/slang/slang-ast-decl.cpp
+++ b/source/slang/slang-ast-decl.cpp
@@ -18,4 +18,18 @@ const TypeExp& TypeConstraintDecl::_getSupOverride() const
 }
 
 
+bool isInterfaceRequirement(Decl* decl)
+{
+    auto ancestor = decl->parentDecl;
+    for (; ancestor; ancestor = ancestor->parentDecl)
+    {
+        if (as<InterfaceDecl>(ancestor))
+            return true;
+
+        if (as<ExtensionDecl>(ancestor))
+            return false;
+    }
+    return false;
+}
+
 } // namespace Slang
diff --git a/source/slang/slang-ast-decl.h b/source/slang/slang-ast-decl.h
index 9d2c99f14..147bc7d22 100644
--- a/source/slang/slang-ast-decl.h
+++ b/source/slang/slang-ast-decl.h
@@ -494,4 +494,7 @@ class AttributeDecl : public ContainerDecl
     SyntaxClass<NodeBase> syntaxClass;
 };
 
+
+bool isInterfaceRequirement(Decl* decl);
+
 } // namespace Slang
diff --git a/source/slang/slang-ast-val.cpp b/source/slang/slang-ast-val.cpp
index 4ed69e282..dd5aff238 100644
--- a/source/slang/slang-ast-val.cpp
+++ b/source/slang/slang-ast-val.cpp
@@ -619,15 +619,15 @@ void PolynomialIntVal::_toTextOverride(StringBuilder& out)
     for (Index i = 0; i < terms.getCount(); i++)
     {
         auto& term = *(terms[i]);
-        if (i > 0)
+        if (term.constFactor > 0)
         {
-            if (term.constFactor > 0)
+            if (i > 0)
                 out << "+";
-            else
-                out << "-";
         }
+        else
+            out << "-";
         bool isFirstFactor = true;
-        if (term.constFactor != 1 || term.paramFactors.getCount() == 0)
+        if (abs(term.constFactor) != 1 || term.paramFactors.getCount() == 0)
         {
             out << abs(term.constFactor);
             isFirstFactor = false;
@@ -1039,19 +1039,19 @@ IntVal* PolynomialIntVal::canonicalize(ASTBuilder* builder)
     return this;
 }
 
-// !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!! SomeIntVal !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
+// !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!! FuncCallIntVal !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
 
-bool SomeIntVal::_equalsValOverride(Val* val)
+bool FuncCallIntVal::_equalsValOverride(Val* val)
 {
-    if (auto someIntVal = as<SomeIntVal>(val))
+    if (auto funcCallIntVal = as<FuncCallIntVal>(val))
     {
-        if (!funcDeclRef.equals(someIntVal->funcDeclRef))
+        if (!funcDeclRef.equals(funcCallIntVal->funcDeclRef))
             return false;
-        if (args.getCount() != someIntVal->args.getCount())
+        if (args.getCount() != funcCallIntVal->args.getCount())
             return false;
         for (Index i = 0; i < args.getCount(); i++)
         {
-            if (!args[i]->equalsVal(someIntVal->args[i]))
+            if (!args[i]->equalsVal(funcCallIntVal->args[i]))
                 return false;
         }
         return true;
@@ -1059,11 +1059,11 @@ bool SomeIntVal::_equalsValOverride(Val* val)
     return false;
 }
 
-void SomeIntVal::_toTextOverride(StringBuilder& out)
+void FuncCallIntVal::_toTextOverride(StringBuilder& out)
 {
     auto argToText = [&](int index)
     {
-        if (as<PolynomialIntVal>(args[index]) || as<SomeIntVal>(args[index]))
+        if (as<PolynomialIntVal>(args[index]) || as<FuncCallIntVal>(args[index]))
         {
             out << "(";
             args[index]->toText(out);
@@ -1110,7 +1110,7 @@ void SomeIntVal::_toTextOverride(StringBuilder& out)
     }
 }
 
-HashCode SomeIntVal::_getHashCodeOverride()
+HashCode FuncCallIntVal::_getHashCodeOverride()
 {
     HashCode result = funcDeclRef.getHashCode();
     for (auto arg : args)
@@ -1127,7 +1127,7 @@ static bool nameIs(Name* name, const char* val)
     return false;
 }
 
-Val* SomeIntVal::tryFoldImpl(ASTBuilder* astBuilder, DeclRef<Decl> newFuncDecl, List<IntVal*>& newArgs, DiagnosticSink* sink)
+Val* FuncCallIntVal::tryFoldImpl(ASTBuilder* astBuilder, DeclRef<Decl> newFuncDecl, List<IntVal*>& newArgs, DiagnosticSink* sink)
 {
     // Are all args const now?
     List<ConstantIntVal*> constArgs;
@@ -1205,14 +1205,14 @@ Val* SomeIntVal::tryFoldImpl(ASTBuilder* astBuilder, DeclRef<Decl> newFuncDecl,
         }
         else
         {
-            SLANG_UNREACHABLE("constant folding of SomeIntVal");
+            SLANG_UNREACHABLE("constant folding of FuncCallIntVal");
         }
         return astBuilder->create<ConstantIntVal>(resultValue);
     }
     return nullptr;
 }
 
-Val* SomeIntVal::_substituteImplOverride(ASTBuilder* astBuilder, SubstitutionSet subst, int* ioDiff)
+Val* FuncCallIntVal::_substituteImplOverride(ASTBuilder* astBuilder, SubstitutionSet subst, int* ioDiff)
 {
     int diff = 0;
     auto newFuncDeclRef = funcDeclRef.substituteImpl(astBuilder, subst, &diff);
@@ -1233,7 +1233,7 @@ Val* SomeIntVal::_substituteImplOverride(ASTBuilder* astBuilder, SubstitutionSet
             return newVal;
         else
         {
-            auto result = astBuilder->create<SomeIntVal>();
+            auto result = astBuilder->create<FuncCallIntVal>();
             result->args = _Move(newArgs);
             result->funcDeclRef = newFuncDeclRef;
             result->funcType = funcType;
@@ -1244,4 +1244,72 @@ Val* SomeIntVal::_substituteImplOverride(ASTBuilder* astBuilder, SubstitutionSet
     return this;
 }
 
+// !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!! WitnessLookupIntVal !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
+
+bool WitnessLookupIntVal::_equalsValOverride(Val* val)
+{
+    if (auto lookupIntVal = as<WitnessLookupIntVal>(val))
+    {
+        if (!witness->equalsVal(lookupIntVal->witness))
+            return false;
+        if (key != lookupIntVal->key)
+            return false;
+        return true;
+    }
+    return false;
+}
+
+void WitnessLookupIntVal::_toTextOverride(StringBuilder& out)
+{
+    witness->sub->toText(out);
+    out << ".";
+    out << (key->getName() ? key->getName()->text : "??");
+}
+
+HashCode WitnessLookupIntVal::_getHashCodeOverride()
+{
+    HashCode result = witness->getHashCode();
+    result = combineHash(result, Slang::getHashCode(key));
+    return result;
+}
+Val* WitnessLookupIntVal::_substituteImplOverride(ASTBuilder* astBuilder, SubstitutionSet subst, int* ioDiff)
+{
+    int diff = 0;
+    auto newWitness = witness->substituteImpl(astBuilder, subst, &diff);
+    *ioDiff += diff;
+    if (diff)
+    {
+        auto witnessEntry = tryFoldOrNull(astBuilder, as<SubtypeWitness>(newWitness), key);
+        if (witnessEntry)
+            return witnessEntry;
+    }
+    // Nothing found: don't substitute.
+    return this;
+}
+
+Val* WitnessLookupIntVal::tryFoldOrNull(ASTBuilder* astBuilder, SubtypeWitness* witness, Decl* key)
+{
+    auto witnessEntry = tryLookUpRequirementWitness(astBuilder, witness, key);
+    switch (witnessEntry.getFlavor())
+    {
+    case RequirementWitness::Flavor::val:
+        return witnessEntry.getVal();
+        break;
+    default:
+        break;
+    }
+    return nullptr;
+}
+
+Val* WitnessLookupIntVal::tryFold(ASTBuilder* astBuilder, SubtypeWitness* witness, Decl* key, Type* type)
+{
+    if (auto result = tryFoldOrNull(astBuilder, witness, key))
+        return result;
+    auto witnessResult = astBuilder->create<WitnessLookupIntVal>();
+    witnessResult->witness = witness;
+    witnessResult->key = key;
+    witnessResult->type = type;
+    return witnessResult;
+}
+
 } // namespace Slang
diff --git a/source/slang/slang-ast-val.h b/source/slang/slang-ast-val.h
index 64f04abf9..259be75c3 100644
--- a/source/slang/slang-ast-val.h
+++ b/source/slang/slang-ast-val.h
@@ -53,9 +53,9 @@ protected:
 };
 
 // An compile time int val as result of some general computation.
-class SomeIntVal : public IntVal
+class FuncCallIntVal : public IntVal
 {
-    SLANG_AST_CLASS(SomeIntVal)
+    SLANG_AST_CLASS(FuncCallIntVal)
 
     bool _equalsValOverride(Val* val);
     void _toTextOverride(StringBuilder& out);
@@ -63,9 +63,28 @@ class SomeIntVal : public IntVal
     Val* _substituteImplOverride(ASTBuilder* astBuilder, SubstitutionSet subst, int* ioDiff);
 
     DeclRef<Decl> funcDeclRef;
-    List<IntVal*> args;
     Type* funcType;
-    static Val* tryFoldImpl(ASTBuilder* astBuilder, DeclRef<Decl> newFuncDecl, List<IntVal*> &newArgs, DiagnosticSink* sink);
+    List<IntVal*> args;
+
+    static Val* tryFoldImpl(ASTBuilder* astBuilder, DeclRef<Decl> newFuncDecl, List<IntVal*>& newArgs, DiagnosticSink* sink);
+};
+
+class WitnessLookupIntVal : public IntVal
+{
+    SLANG_AST_CLASS(WitnessLookupIntVal)
+
+    bool _equalsValOverride(Val* val);
+    void _toTextOverride(StringBuilder& out);
+    HashCode _getHashCodeOverride();
+    Val* _substituteImplOverride(ASTBuilder* astBuilder, SubstitutionSet subst, int* ioDiff);
+
+    SubtypeWitness* witness;
+    Decl* key;
+    Type* type;
+
+    static Val* tryFoldOrNull(ASTBuilder* astBuilder, SubtypeWitness* witness, Decl* key);
+
+    static Val* tryFold(ASTBuilder* astBuilder, SubtypeWitness* witness, Decl* key, Type* type);
 };
 
 // polynomial expression "2*a*b^3 + 1" will be represented as:
diff --git a/source/slang/slang-check-decl.cpp b/source/slang/slang-check-decl.cpp
index abe7642fb..9e3fbaa8d 100644
--- a/source/slang/slang-check-decl.cpp
+++ b/source/slang/slang-check-decl.cpp
@@ -1053,6 +1053,33 @@ namespace Slang
                 addModifier(varDecl, m_astBuilder->create<NVAPIMagicModifier>());
             }
         }
+
+        if (auto interfaceDecl = as<InterfaceDecl>(varDecl->parentDecl))
+        {
+            if (auto basicType = as<BasicExpressionType>(varDecl->getType()))
+            {
+                switch (basicType->baseType)
+                {
+                case BaseType::Bool:
+                case BaseType::Int8:
+                case BaseType::Int16:
+                case BaseType::Int:
+                case BaseType::Int64:
+                case BaseType::UInt8:
+                case BaseType::UInt16:
+                case BaseType::UInt:
+                case BaseType::UInt64:
+                    break;
+                default:
+                    getSink()->diagnose(varDecl, Diagnostics::staticConstRequirementMustBeIntOrBool);
+                    break;
+                }
+            }
+            if (!varDecl->findModifier<HLSLStaticModifier>() || !varDecl->findModifier<ConstModifier>())
+            {
+                getSink()->diagnose(varDecl, Diagnostics::valueRequirementMustBeCompileTimeConst);
+            }
+        }
     }
 
     void SemanticsDeclHeaderVisitor::visitStructDecl(StructDecl* structDecl)
@@ -1588,6 +1615,47 @@ namespace Slang
         return true;
     }
 
+    bool SemanticsVisitor::doesVarMatchRequirement(
+        DeclRef<VarDeclBase>   satisfyingMemberDeclRef,
+        DeclRef<VarDeclBase>   requiredMemberDeclRef,
+        RefPtr<WitnessTable>    witnessTable)
+    {
+        // The type of the satisfying member must match the type of the required member.
+        auto satisfyingType = getType(getASTBuilder(), satisfyingMemberDeclRef);
+        auto requiredType = getType(getASTBuilder(), requiredMemberDeclRef);
+        if (!satisfyingType->equals(requiredType))
+            return false;
+
+        for (auto modifier : requiredMemberDeclRef.getDecl()->modifiers)
+        {
+            bool found = false;
+            for (auto satisfyingModifier : satisfyingMemberDeclRef.getDecl()->modifiers)
+            {
+                if (satisfyingModifier->astNodeType == modifier->astNodeType)
+                {
+                    found = true;
+                    break;
+                }
+            }
+            if (!found)
+                return false;
+        }
+
+        auto satisfyingVal = tryConstantFoldDeclRef(satisfyingMemberDeclRef, nullptr);
+        if (satisfyingVal)
+        {
+            witnessTable->add(
+                requiredMemberDeclRef,
+                RequirementWitness(satisfyingVal));
+        }
+        else
+        {
+            witnessTable->add(
+                requiredMemberDeclRef.getDecl(),
+                RequirementWitness(satisfyingMemberDeclRef));
+        }
+        return true;
+    }
 
     bool SemanticsVisitor::doesGenericSignatureMatchRequirement(
         DeclRef<GenericDecl>        satisfyingGenericDeclRef,
@@ -1975,6 +2043,14 @@ namespace Slang
                 return doesPropertyMatchRequirement(propertyDeclRef, requiredPropertyDeclRef, witnessTable);
             }
         }
+        else if (auto varDeclRef = memberDeclRef.as<VarDeclBase>())
+        {
+            if (auto requiredVarDeclRef = requiredMemberDeclRef.as<VarDeclBase>())
+            {
+                ensureDecl(varDeclRef, DeclCheckState::SignatureChecked);
+                return doesVarMatchRequirement(varDeclRef, requiredVarDeclRef, witnessTable);
+            }
+        }
         // Default: just assume that thing aren't being satisfied.
         return false;
     }
diff --git a/source/slang/slang-check-expr.cpp b/source/slang/slang-check-expr.cpp
index 8e14af72a..e33d26c0c 100644
--- a/source/slang/slang-check-expr.cpp
+++ b/source/slang/slang-check-expr.cpp
@@ -982,7 +982,7 @@ namespace Slang
                 || opName == getName("|") || opName == getName("&") || opName == getName("^") || opName == getName("~") || opName == getName("%") ||
                 opName == getName("?:") || opName == getName("<<") || opName == getName(">>"))
             {
-                auto result = m_astBuilder->create<SomeIntVal>();
+                auto result = m_astBuilder->create<FuncCallIntVal>();
                 result->args.addRange(argVals, argCount);
                 result->funcDeclRef = funcDeclRef;
                 result->funcType = as<Type>(funcDeclRefExpr.getExpr()->type->substitute(
@@ -1131,6 +1131,22 @@ namespace Slang
         if(!decl->hasModifier<ConstModifier>())
             return nullptr;
 
+        if (isInterfaceRequirement(decl))
+        {
+            for (auto subst = declRef.substitutions.substitutions; subst; subst = subst->outer)
+            {
+                if (auto thisTypeSubst = as<ThisTypeSubstitution>(subst))
+                {
+                    auto val = WitnessLookupIntVal::tryFold(
+                        m_astBuilder,
+                        thisTypeSubst->witness,
+                        decl,
+                        declRef.substitute(m_astBuilder, decl->type.type));
+                    return as<IntVal>(val);
+                }
+            }
+        }
+
         auto initExpr = getInitExpr(m_astBuilder, declRef);
         if(!initExpr)
             return nullptr;
diff --git a/source/slang/slang-check-impl.h b/source/slang/slang-check-impl.h
index 9a849384c..091990cf3 100644
--- a/source/slang/slang-check-impl.h
+++ b/source/slang/slang-check-impl.h
@@ -898,6 +898,10 @@ namespace Slang
             DeclRef<PropertyDecl>   satisfyingMemberDeclRef,
             DeclRef<PropertyDecl>   requiredMemberDeclRef,
             RefPtr<WitnessTable>    witnessTable);
+        bool doesVarMatchRequirement(
+            DeclRef<VarDeclBase>   satisfyingMemberDeclRef,
+            DeclRef<VarDeclBase>   requiredMemberDeclRef,
+            RefPtr<WitnessTable>    witnessTable);
 
         bool doesGenericSignatureMatchRequirement(
             DeclRef<GenericDecl>        genDecl,
diff --git a/source/slang/slang-diagnostic-defs.h b/source/slang/slang-diagnostic-defs.h
index 27076681d..c3062ea4f 100644
--- a/source/slang/slang-diagnostic-defs.h
+++ b/source/slang/slang-diagnostic-defs.h
@@ -338,6 +338,8 @@ DIAGNOSTIC(32003, Error, unexpectedEnumTagExpr,     "unexpected form for 'enum'
 // 303xx: interfaces and associated types
 DIAGNOSTIC(30300, Error, assocTypeInInterfaceOnly, "'associatedtype' can only be defined in an 'interface'.")
 DIAGNOSTIC(30301, Error, globalGenParamInGlobalScopeOnly, "'type_param' can only be defined global scope.")
+DIAGNOSTIC(30302, Error, staticConstRequirementMustBeIntOrBool, "'static const' requirement can only have int or bool type.")
+DIAGNOSTIC(30303, Error, valueRequirementMustBeCompileTimeConst, "requirement in the form of a simple value must be declared as 'static const'.")
 
 // Interop
 DIAGNOSTIC(30400, Error, cannotDefinePtrTypeToManagedResource, "pointer to a managed resource is invalid, use `NativeRef<T>` instead")
diff --git a/source/slang/slang-lower-to-ir.cpp b/source/slang/slang-lower-to-ir.cpp
index b351bfe21..0921d36fb 100644
--- a/source/slang/slang-lower-to-ir.cpp
+++ b/source/slang/slang-lower-to-ir.cpp
@@ -1199,6 +1199,9 @@ bool shouldDeclBeTreatedAsInterfaceRequirement(Decl* requirementDecl)
     else if (auto typeConstraint = as<TypeConstraintDecl>(requirementDecl))
     {
     }
+    else if (auto varDecl = as<VarDeclBase>(requirementDecl))
+    {
+    }
     else if (auto genericDecl = as<GenericDecl>(requirementDecl))
     {
         return shouldDeclBeTreatedAsInterfaceRequirement(genericDecl->inner);
@@ -1287,7 +1290,7 @@ struct ValLoweringVisitor : ValVisitor<ValLoweringVisitor, LoweredValInfo, Lower
             lowerType(context, getType(context->astBuilder, val->declRef)));
     }
 
-    LoweredValInfo visitSomeIntVal(SomeIntVal* val)
+    LoweredValInfo visitFuncCallIntVal(FuncCallIntVal* val)
     {
         TryClauseEnvironment tryEnv;
         List<IRInst*> args;
@@ -1306,6 +1309,15 @@ struct ValLoweringVisitor : ValVisitor<ValLoweringVisitor, LoweredValInfo, Lower
             tryEnv);
     }
 
+    LoweredValInfo visitWitnessLookupIntVal(WitnessLookupIntVal* val)
+    {
+        auto witnessVal = lowerVal(context, val->witness);
+        auto key = getInterfaceRequirementKey(context, val->key);
+        auto type = lowerType(context, val->type);
+        return LoweredValInfo::simple(getBuilder()->emitLookupInterfaceMethodInst(
+            type, witnessVal.val, key));
+    }
+
     LoweredValInfo visitPolynomialIntVal(PolynomialIntVal* val)
     {
         auto irBuilder = getBuilder();
@@ -8259,20 +8271,6 @@ bool canDeclLowerToAGeneric(Decl* decl)
     return false;
 }
 
-static bool isInterfaceRequirement(Decl* decl)
-{
-    auto ancestor = decl->parentDecl;
-    for (; ancestor; ancestor = ancestor->parentDecl)
-    {
-        if (as<InterfaceDecl>(ancestor))
-            return true;
-
-        if (as<ExtensionDecl>(ancestor))
-            return false;
-    }
-    return false;
-}
-
     /// Add flattened "leaf" elements from `val` to the `ioArgs` list
 static void _addFlattenedTupleArgs(
     List<IRInst*>&  ioArgs,