Improved generic constraint const conversion handling

IDEHelper/Compiler/BfIRBuilder.cpp

@@ -461,6 +461,18 @@ int BfIRConstHolder::IsZero(BfIRValue value)
 	return -1;
 }
 
+bool BfIRConstHolder::IsConstValue(BfIRValue value)
+{
+	auto constant = GetConstant(value);
+	if (constant == NULL)
+		return false;
+
+	if (constant->mConstType == BfConstType_GlobalVar)
+		return false;
+
+	return true;
+}
+
 int BfIRConstHolder::CheckConstEquality(BfIRValue lhs, BfIRValue rhs)
 {
 	auto constLHS = GetConstant(lhs);

IDEHelper/Compiler/BfIRBuilder.h

@@ -948,6 +948,7 @@ public:
 	BfConstant* GetConstant(BfIRValue id);
 	bool TryGetBool(BfIRValue id, bool& boolVal);
 	int IsZero(BfIRValue val);
+	bool IsConstValue(BfIRValue val);
 	int CheckConstEquality(BfIRValue lhs, BfIRValue rhs); // -1 = fail, 0 = false, 1 = true
 	//void WriteConstant(void* data, BeConstant* constVal);
 
@@ -970,7 +971,7 @@ public:
 	BfIRValue CreateGlobalVariableConstant(BfIRType varType, bool isConstant, BfIRLinkageType linkageType, BfIRValue initializer, const StringImpl& name, bool isTLS = false);
 
 	bool WriteConstant(BfIRValue val, void* ptr, BfType* type);
-	BfIRValue ReadConstant(void* ptr, BfType* type);
+	BfIRValue ReadConstant(void* ptr, BfType* type);	
 };
 
 enum BfIRPopulateType

IDEHelper/Compiler/BfModuleTypeUtils.cpp

@@ -13510,7 +13510,15 @@ BfIRValue BfModule::CastToValue(BfAstNode* srcNode, BfTypedValue typedVal, BfTyp
 								// .. and we can convert the constraint's toType to OUR toType then we're good
 								auto opToVal = genericParam->mExternType;
 								if (CanCast(BfTypedValue(BfIRValue::sValueless, opToVal), toType, BfCastFlags_NoConversionOperator))
-									return mBfIRBuilder->GetFakeVal();
+								{
+									if (mBfIRBuilder->IsConstValue(typedVal.mValue))
+									{
+										// Retain constness
+										return mBfIRBuilder->GetUndefConstValue(mBfIRBuilder->MapType(toType));
+									}
+									else
+										return mBfIRBuilder->GetFakeVal();
+								}
 							}
 						}
 					}
@@ -13535,7 +13543,15 @@ BfIRValue BfModule::CastToValue(BfAstNode* srcNode, BfTypedValue typedVal, BfTyp
 								// .. and we can convert the constraint's toType to OUR toType then we're good
 								auto opToVal = genericParam->mExternType;
 								if (CanCast(BfTypedValue(BfIRValue::sValueless, opToVal), toType, BfCastFlags_NoConversionOperator))
-									return mBfIRBuilder->GetFakeVal();
+								{
+									if (mBfIRBuilder->IsConstValue(typedVal.mValue))
+									{
+										// Retain constness
+										return mBfIRBuilder->GetUndefConstValue(mBfIRBuilder->MapType(toType));
+									}
+									else
+										return mBfIRBuilder->GetFakeVal();
+								}
 							}
 						}
 					}

IDEHelper/Compiler/CeMachine.cpp

@@ -4409,6 +4409,9 @@ BfIRValue CeContext::CreateConstant(BfModule* module, uint8* ptr, BfType* bfType
 	if (bfType->IsTypedPrimitive())
 		return CreateConstant(module, ptr, bfType->GetUnderlyingType(), outType);
 
+	if (bfType->IsGenericParam())
+		return irBuilder->GetUndefConstValue(irBuilder->MapType(bfType));
+
 	if (bfType->IsTypeInstance())
 	{
 		auto typeInst = bfType->ToTypeInstance();