From 1a9366041620c30dcf032d6e614fe45666b05382 Mon Sep 17 00:00:00 2001
From: Brian Fiete <bfiete@gmail.com>
Date: Mon, 18 Apr 2022 07:57:15 -0700
Subject: [PATCH] Better handling of undef const expressions

---
 IDEHelper/Compiler/BfExprEvaluator.cpp   |  8 ++++++++
 IDEHelper/Compiler/BfModuleTypeUtils.cpp | 19 ++++++++++++++++++-
 IDEHelper/Compiler/BfResolvedTypeUtils.h |  3 +++
 IDEHelper/Tests/src/Generics2.bf         | 13 +++++++++++++
 4 files changed, 42 insertions(+), 1 deletion(-)

diff --git a/IDEHelper/Compiler/BfExprEvaluator.cpp b/IDEHelper/Compiler/BfExprEvaluator.cpp
index 8e21cf33..96a16a9d 100644
--- a/IDEHelper/Compiler/BfExprEvaluator.cpp
+++ b/IDEHelper/Compiler/BfExprEvaluator.cpp
@@ -3801,6 +3801,14 @@ void BfExprEvaluator::GetLiteral(BfAstNode* refNode, const BfVariant& variant)
 	case BfTypeCode_StringId:
 		mResult = BfTypedValue(mModule->mBfIRBuilder->CreateConst(variant.mTypeCode, variant.mUInt64), mModule->ResolveTypeDef(mModule->mCompiler->mStringTypeDef));
 		break;
+	case BfTypeCode_Let:
+		if (mExpectingType != NULL)
+		{
+			mResult = BfTypedValue(mModule->mBfIRBuilder->CreateUndefValue(mModule->mBfIRBuilder->MapType(mExpectingType)), mExpectingType);
+			break;
+		}
+		mModule->Fail("Invalid undef literal", refNode);
+		break;
 	default:
 		mModule->Fail("Invalid literal", refNode);
 		break;
diff --git a/IDEHelper/Compiler/BfModuleTypeUtils.cpp b/IDEHelper/Compiler/BfModuleTypeUtils.cpp
index 67799300..dd817125 100644
--- a/IDEHelper/Compiler/BfModuleTypeUtils.cpp
+++ b/IDEHelper/Compiler/BfModuleTypeUtils.cpp
@@ -6903,7 +6903,19 @@ BfConstExprValueType* BfModule::CreateConstExprValueType(const BfTypedValue& typ
 	BfResolveTypeRefFlags resolveFlags = allowCreate ? BfResolveTypeRefFlag_None : BfResolveTypeRefFlag_NoCreate;
 
 	auto variant = TypedValueToVariant(NULL, typedValue);
+
 	if (variant.mTypeCode == BfTypeCode_None)
+	{
+		if (auto constant = mBfIRBuilder->GetConstant(typedValue.mValue))
+		{
+			if (constant->mConstType == BfConstType_Undef)
+			{
+				variant.mTypeCode = BfTypeCode_Let;
+			}
+		}
+	}
+
+	if (variant.mTypeCode == BfTypeCode_None)	
 		return NULL;
 
 	auto constExprValueType = mContext->mConstExprValueTypePool.Get();
@@ -12895,7 +12907,7 @@ BfIRValue BfModule::CastToValue(BfAstNode* srcNode, BfTypedValue typedVal, BfTyp
 		{
 			BfConstExprValueType* toConstExprValueType = (BfConstExprValueType*)toType;
 			
-			auto variantVal = TypedValueToVariant(srcNode, typedVal);
+			auto variantVal = TypedValueToVariant(srcNode, typedVal, true);
 			if ((mBfIRBuilder->IsIntable(variantVal.mTypeCode)) && (mBfIRBuilder->IsIntable(toConstExprValueType->mValue.mTypeCode)))
 			{
 				if (variantVal.mInt64 == toConstExprValueType->mValue.mInt64)
@@ -12914,6 +12926,11 @@ BfIRValue BfModule::CastToValue(BfAstNode* srcNode, BfTypedValue typedVal, BfTyp
 					return typedVal.mValue;
 			}
 
+			if ((toConstExprValueType->mValue.mTypeCode == BfTypeCode_Let) && (constant->mConstType == BfConstType_Undef))
+			{
+				return typedVal.mValue;
+			}
+
 			if (!ignoreErrors)
 			{
 				String valStr;
diff --git a/IDEHelper/Compiler/BfResolvedTypeUtils.h b/IDEHelper/Compiler/BfResolvedTypeUtils.h
index 2ab7b5b9..3ee4d82f 100644
--- a/IDEHelper/Compiler/BfResolvedTypeUtils.h
+++ b/IDEHelper/Compiler/BfResolvedTypeUtils.h
@@ -2511,6 +2511,9 @@ public:
 
 	virtual bool IsConstExprValue() override { return true; }
 	virtual BfType* GetUnderlyingType() override { return mType; }
+
+	virtual bool IsUnspecializedType() { return mValue.mTypeCode == BfTypeCode_Let; }
+	virtual bool IsUnspecializedTypeVariation() { return mValue.mTypeCode == BfTypeCode_Let; }
 };
 
 /*class BfCustomAttributeArgument
diff --git a/IDEHelper/Tests/src/Generics2.bf b/IDEHelper/Tests/src/Generics2.bf
index 0809055a..9eeb99af 100644
--- a/IDEHelper/Tests/src/Generics2.bf
+++ b/IDEHelper/Tests/src/Generics2.bf
@@ -121,6 +121,18 @@ namespace Tests
 			return total;
 		}
 
+		public static int StrTest<T>(T param2)
+			where T : const String
+		{
+			return StrTest2(param2);
+		}
+
+		public static int StrTest2<T>(T param1)
+			where T : const String
+		{
+			return param1.Length;
+		}
+
 		[Test]
 		public static void TestBasics()
 		{
@@ -136,6 +148,7 @@ namespace Tests
 
 			Test.Assert(BigNum<const 3>.N == 3);
 			Test.Assert(Test("test", 1, 2, 3) == 10);
+			Test.Assert(StrTest("ABCDE") == 5);
 		}
 	}
 }