Support unscoped enums. (#3771)

6 files changed, 47 insertions, 4 deletions

diff --git a/docs/user-guide/02-conventional-features.md b/docs/user-guide/02-conventional-features.md
index 4faa6607b..8c45fec48 100644
--- a/docs/user-guide/02-conventional-features.md
+++ b/docs/user-guide/02-conventional-features.md
@@ -158,8 +158,18 @@ enum Channel
 }
 ```
 
-> #### Note ####
-> Unlike C/C++, `enum` types in Slang are always scoped (like `enum class` in C++). You can write `enum class` in Slang if it makes you happy, but it isn't required.
+Unlike C/C++, `enum` types in Slang are always scoped by default (like `enum class` in C++). You can write `enum class` in Slang if it makes you happy, but it isn't required. If you want a `enum` type to be unscoped, you can use the `[UnscopedEnum]` attribute:
+```csharp
+[[UnscopedEnum]
+enum Channel
+{
+    Red, Green, Blue
+}
+void test(Channel c)
+{
+    if (c == Red) { /*...*/ }
+}
+```
 
 ### Opaque Types
 
diff --git a/source/slang/core.meta.slang b/source/slang/core.meta.slang
index 54a82c4f0..237daac56 100644
--- a/source/slang/core.meta.slang
+++ b/source/slang/core.meta.slang
@@ -2345,6 +2345,9 @@ attribute_syntax [spv_target_env_1_3] : SPIRVTargetEnv13Attribute;
 __attributeTarget(VarDeclBase)
 attribute_syntax [disable_array_flattening] : DisableArrayFlatteningAttribute;
 
+__attributeTarget(EnumDecl)
+attribute_syntax [UnscopedEnum] : UnscopedEnumAttribute;
+
 // Statement Attributes
 
 __attributeTarget(LoopStmt)
diff --git a/source/slang/slang-ast-modifier.h b/source/slang/slang-ast-modifier.h
index 49dc1b81f..32852496c 100644
--- a/source/slang/slang-ast-modifier.h
+++ b/source/slang/slang-ast-modifier.h
@@ -713,6 +713,10 @@ class CallAttribute : public Attribute
 };
                // `[call]`
 
+class UnscopedEnumAttribute : public Attribute
+{
+    SLANG_AST_CLASS(UnscopedEnumAttribute)
+};
 
 // [[vk_push_constant]] [[push_constant]]
 class PushConstantAttribute : public Attribute 
diff --git a/source/slang/slang-check-modifier.cpp b/source/slang/slang-check-modifier.cpp
index 6359096b9..eae993dc7 100644
--- a/source/slang/slang-check-modifier.cpp
+++ b/source/slang/slang-check-modifier.cpp
@@ -1173,7 +1173,15 @@ namespace Slang
             // the right syntax class to instantiate.
             //
 
-            return checkAttribute(hlslUncheckedAttribute, syntaxNode);
+            auto checkedAttr = checkAttribute(hlslUncheckedAttribute, syntaxNode);
+
+            if (as<UnscopedEnumAttribute>(checkedAttr))
+            {
+                if (auto parentDecl = as<ContainerDecl>(getParentDecl(as<Decl>(syntaxNode))))
+                    parentDecl->invalidateMemberDictionary();
+                return getASTBuilder()->create<TransparentModifier>();
+            }
+            return checkedAttr;
         }
 
         if (auto decl = as<Decl>(syntaxNode))
diff --git a/source/slang/slang-lookup.cpp b/source/slang/slang-lookup.cpp
index 04a855c3c..301c86aa8 100644
--- a/source/slang/slang-lookup.cpp
+++ b/source/slang/slang-lookup.cpp
@@ -648,7 +648,8 @@ static void _lookUpMembersInValue(
     // in the *type* of that value.
     //
     auto valueType = getTypeForDeclRef(astBuilder, valueDeclRef, SourceLoc());
-
+    if (auto typeType = as<TypeType>(valueType))
+        valueType = typeType->getType();
     return _lookUpMembersInType(astBuilder, name, valueType, request, ioResult, breadcrumbs);
 }
 
diff --git a/tests/language-feature/enums/unscoped-enum.slang b/tests/language-feature/enums/unscoped-enum.slang
new file mode 100644
index 000000000..6d6558268
--- /dev/null
+++ b/tests/language-feature/enums/unscoped-enum.slang
@@ -0,0 +1,17 @@
+//TEST(compute):COMPARE_COMPUTE(filecheck-buffer=CHECK): -shaderobj
+
+[UnscopedEnum]
+enum class Fruit
+{
+    Orange, Apple
+}
+
+//TEST_INPUT:ubuffer(data=[0 0 0 0], stride=4):out,name=outputBuffer
+RWStructuredBuffer<uint> outputBuffer;
+
+[numthreads(1,1,1)]
+void computeMain()
+{
+    // CHECK: 1
+    outputBuffer[0] = (int)Apple;
+}
\ No newline at end of file