From e6352571c1ca61681d6e363d7d948d7412f3bd23 Mon Sep 17 00:00:00 2001
From: Brian Fiete <bfiete@gmail.com>
Date: Wed, 3 Aug 2022 07:54:35 -0700
Subject: [PATCH] Fixed nullable null coalescing short circuiting

---
 BeefLibs/corlib/src/Nullable.bf        | 25 -------------------------
 IDEHelper/Compiler/BfExprEvaluator.cpp | 22 +++++++++++++++++-----
 IDEHelper/Tests/src/Nullable.bf        | 17 +++++++++++++++++
 3 files changed, 34 insertions(+), 30 deletions(-)

diff --git a/BeefLibs/corlib/src/Nullable.bf b/BeefLibs/corlib/src/Nullable.bf
index 6172ee57..6830b790 100644
--- a/BeefLibs/corlib/src/Nullable.bf
+++ b/BeefLibs/corlib/src/Nullable.bf
@@ -420,31 +420,6 @@ namespace System
             return Nullable<TResult>(lhs.mValue | rhs.mValue);
         }
 
-        //
-
-		public static T operator??(Nullable<T> lhs, T rhs)
-		{
-		    return (lhs.mHasValue) ? lhs.mValue : rhs;
-		}
-
-        public static TResult? operator??<TOther, TResult>(TOther lhs, Nullable<T> rhs) where TResult : operator TOther ?? T where TResult : struct
-        {
-            if (!rhs.mHasValue) return null;
-            return Nullable<TResult>(lhs ?? rhs.mValue);
-        }
-
-        public static TResult? operator??<TOther, TResult>(Nullable<T> lhs, TOther rhs) where TResult : operator T ?? TOther where TResult : struct
-        {
-            if (!lhs.mHasValue) return null;
-            return Nullable<TResult>(lhs.mValue ?? rhs);
-        }
-
-        public static TResult? operator??<TOther, TResult>(Nullable<T> lhs, Nullable<TOther> rhs) where TOther : struct where TResult : operator T ?? TOther where TResult : struct
-        {
-            if ((!lhs.mHasValue) || (!rhs.mHasValue)) return null;
-            return Nullable<TResult>(lhs.mValue ?? rhs.mValue);
-        }
-
         //
 
         public static TResult? operator<< <TOther, TResult>(TOther lhs, Nullable<T> rhs) where TResult : operator TOther << T where TResult : struct
diff --git a/IDEHelper/Compiler/BfExprEvaluator.cpp b/IDEHelper/Compiler/BfExprEvaluator.cpp
index c20dfb82..c11889a0 100644
--- a/IDEHelper/Compiler/BfExprEvaluator.cpp
+++ b/IDEHelper/Compiler/BfExprEvaluator.cpp
@@ -22925,17 +22925,21 @@ void BfExprEvaluator::PerformBinaryOperation(BfExpression* leftExpression, BfExp
 
 bool BfExprEvaluator::PerformBinaryOperation_NullCoalesce(BfTokenNode* opToken, BfExpression* leftExpression, BfExpression* rightExpression, BfTypedValue leftValue, BfType* wantType, BfTypedValue* assignTo)
 {
-	if ((leftValue) && ((leftValue.mType->IsPointer()) || (leftValue.mType->IsFunction()) || (leftValue.mType->IsObject())) /* || (leftValue.mType->IsNullable())*/)
+	if ((leftValue) && ((leftValue.mType->IsPointer()) || (leftValue.mType->IsFunction()) || (leftValue.mType->IsObject())) || (leftValue.mType->IsNullable()))
 	{
 		leftValue = mModule->LoadValue(leftValue);
 
+		BfType* nullableElementType = NULL;
 		BfIRValue nullableHasValue;
+		BfTypedValue nullableExtractedLeftValue;
 		if (leftValue.mType->IsNullable())
 		{
-			if (wantType == leftValue.mType)
-				wantType = leftValue.mType->GetUnderlyingType();
-			nullableHasValue = mModule->mBfIRBuilder->CreateExtractValue(leftValue.mValue, 1);
-			leftValue = BfTypedValue(mModule->mBfIRBuilder->CreateExtractValue(leftValue.mValue, 0), leftValue.mType->GetUnderlyingType());
+			nullableElementType = leftValue.mType->GetUnderlyingType();
+			nullableHasValue = mModule->mBfIRBuilder->CreateExtractValue(leftValue.mValue, nullableElementType->IsValuelessType() ? 1 : 2); // has_value
+			if (!nullableElementType->IsValuelessType())
+				nullableExtractedLeftValue = BfTypedValue(mModule->mBfIRBuilder->CreateExtractValue(leftValue.mValue, 1), nullableElementType); // value
+			else
+				nullableExtractedLeftValue = BfTypedValue(mModule->mBfIRBuilder->GetFakeVal(), nullableElementType);
 		}
 
 		if (leftValue.mValue.IsConst())
@@ -22984,6 +22988,14 @@ bool BfExprEvaluator::PerformBinaryOperation_NullCoalesce(BfTokenNode* opToken,
 			mModule->AssertErrorState();
 			return true;
 		}
+
+		if ((assignTo == NULL) && (leftValue.mType->IsNullable()) && (!rightValue.mType->IsNullable()))
+		{
+			if (wantType == leftValue.mType)
+				wantType = nullableElementType;
+			leftValue = nullableExtractedLeftValue;
+		}
+
 		rightValue = mModule->LoadValue(rightValue);
 
 		if (assignTo == NULL)
diff --git a/IDEHelper/Tests/src/Nullable.bf b/IDEHelper/Tests/src/Nullable.bf
index 284302a8..237d0542 100644
--- a/IDEHelper/Tests/src/Nullable.bf
+++ b/IDEHelper/Tests/src/Nullable.bf
@@ -1,6 +1,7 @@
 #pragma warning disable 168
 
 using System;
+using System.Collections;
 
 namespace Tests
 {
@@ -97,6 +98,22 @@ namespace Tests
 
 			String str = "Abc";
 			StringView? svn = str;
+
+			iNull = null;
+			int? iNull2 = 123;
+			List<int> l = null;
+			List<int> l2 = scope .();
+
+			int a = iNull2 ?? l.Count;
+			int b = iNull ?? l2.Count;
+			var c = iNull ?? iNull2;
+
+			Test.Assert(a == 123);
+			Test.Assert(b == 0);
+			Test.Assert(typeof(decltype(c)) == typeof(int?));
+
+			iNull ??= iNull2;
+			Test.Assert(iNull == 123);
 		}
 	}
 }