From 318adcc27b8d89ec1d47c445a93239dd81be0b31 Mon Sep 17 00:00:00 2001
From: Yong He <yonghe@outlook.com>
Date: Wed, 12 Jun 2024 09:45:26 -0700
Subject: Add compiler option to treat enum types as unscoped. (#4354)

---
 slang.h                                            |  1 +
 source/slang/slang-lookup.cpp                      |  6 +++++
 source/slang/slang-options.cpp                     |  4 +++-
 source/slang/slang-parser.cpp                      | 28 ++++++++++++++++++++--
 tests/language-feature/enums/anonymous-enum.slang  | 19 +++++++++++++++
 .../enums/unscoped-enum-option.slang               | 19 +++++++++++++++
 6 files changed, 74 insertions(+), 3 deletions(-)
 create mode 100644 tests/language-feature/enums/anonymous-enum.slang
 create mode 100644 tests/language-feature/enums/unscoped-enum-option.slang

diff --git a/slang.h b/slang.h
index d807efec4..ea87daeb4 100644
--- a/slang.h
+++ b/slang.h
@@ -865,6 +865,7 @@ extern "C"
             MinimumSlangOptimization, // bool
             DisableNonEssentialValidations, // bool
             DisableSourceMap,       // bool
+            UnscopedEnum,           // bool
             PreserveParameters,       // bool: preserve all resource parameters in the output code.
 
             // Target
diff --git a/source/slang/slang-lookup.cpp b/source/slang/slang-lookup.cpp
index 5e30e3ce9..c1895d754 100644
--- a/source/slang/slang-lookup.cpp
+++ b/source/slang/slang-lookup.cpp
@@ -224,6 +224,12 @@ static void _lookUpDirectAndTransparentMembers(
         }
     }
 
+    // Don't look up transparent members if we are looking for attributes, since
+    // they are always defined at global scope in the stdlib. Trying to lookup transparent
+    // members during attribute lookup can lead to infinite recursion on transparent types.
+    if ((int)request.mask & (int)LookupMask::Attribute)
+        return;
+
     for(auto transparentInfo : containerDecl->getTransparentMembers())
     {
         // The reference to the transparent member should use the same
diff --git a/source/slang/slang-options.cpp b/source/slang/slang-options.cpp
index aefb14deb..04d48c85f 100644
--- a/source/slang/slang-options.cpp
+++ b/source/slang/slang-options.cpp
@@ -347,6 +347,7 @@ void initCommandOptions(CommandOptions& options)
         { OptionKind::SourceEmbedLanguage, "-source-embed-language", "-source-embed-language <language>",
         "The language to be used for source embedding. Defaults to C/C++. Currently only C/C++ are supported"},
         { OptionKind::DisableShortCircuit, "-disable-short-circuit", nullptr, "Disable short-circuiting for \"&&\" and \"||\" operations" },
+        { OptionKind::UnscopedEnum, "-unscoped-enum", nullptr, "Treat enums types as unscoped by default."}
         { OptionKind::PreserveParameters, "-preserve-params", nullptr, "Preserve all resource parameters in the output code, even if they are not used by the shader."}
     };
 
@@ -1705,8 +1706,9 @@ SlangResult OptionsParser::_parse(
             case OptionKind::NoHLSLBinding:
             case OptionKind::NoHLSLPackConstantBufferElements:
             case OptionKind::LoopInversion:
+            case OptionKind::UnscopedEnum:
             case OptionKind::PreserveParameters:
-                linkage->m_optionSet.set(optionKind, true); break;
+                linkage->m_optionSet.set(optionKind, true);
                 break;
             case OptionKind::MatrixLayoutRow:
             case OptionKind::MatrixLayoutColumn:
diff --git a/source/slang/slang-parser.cpp b/source/slang/slang-parser.cpp
index f5a217354..3d9f1c199 100644
--- a/source/slang/slang-parser.cpp
+++ b/source/slang/slang-parser.cpp
@@ -4907,14 +4907,38 @@ namespace Slang
         // TODO: diagnose this with a warning some day, and move
         // toward deprecating it.
         //
-        AdvanceIf(parser, "class");
+        bool isEnumClass = AdvanceIf(parser, "class");
+        bool isUnscoped = false;
+
+        if (!isEnumClass)
+        {
+            if (parser->options.optionSet.getBoolOption(CompilerOptionName::UnscopedEnum))
+            {
+                isUnscoped = true;
+            }
+        }
 
         AdvanceIf(parser, TokenType::CompletionRequest);
 
         parser->FillPosition(decl);
 
-        decl->nameAndLoc = expectIdentifier(parser);
+        if (parser->tokenReader.peekTokenType() != TokenType::Identifier)
+        {
+            decl->nameAndLoc.name = generateName(parser);
+            decl->nameAndLoc.loc = decl->loc;
+            isUnscoped = true;
+        }
+        else
+        {
+            decl->nameAndLoc = expectIdentifier(parser);
+        }
 
+        // If the type needs to be unscoped, insert modifiers to make it so.
+        if (isUnscoped)
+        {
+            addModifier(decl, parser->astBuilder->create<UnscopedEnumAttribute>());
+            addModifier(decl, parser->astBuilder->create<TransparentModifier>());
+        }
 
         return parseOptGenericDecl(parser, [&](GenericDecl*)
         {
diff --git a/tests/language-feature/enums/anonymous-enum.slang b/tests/language-feature/enums/anonymous-enum.slang
new file mode 100644
index 000000000..b9b0a8c00
--- /dev/null
+++ b/tests/language-feature/enums/anonymous-enum.slang
@@ -0,0 +1,19 @@
+//TEST:SIMPLE(filecheck=CHECK): -target spirv
+
+// CHECK: OpEntryPoint
+
+enum
+{
+    Red,Green,Blue
+}
+
+RWStructuredBuffer<int> buffer;
+[numthreads(1, 1, 1)]
+void main(int id: SV_DispatchThreadID)
+{
+    if (id == Red)
+    {
+        buffer[0] = Green;
+    }
+    buffer[1] = Blue;
+}
diff --git a/tests/language-feature/enums/unscoped-enum-option.slang b/tests/language-feature/enums/unscoped-enum-option.slang
new file mode 100644
index 000000000..4628ac235
--- /dev/null
+++ b/tests/language-feature/enums/unscoped-enum-option.slang
@@ -0,0 +1,19 @@
+//TEST:SIMPLE(filecheck=CHECK): -target spirv -unscoped-enum
+
+// CHECK: OpEntryPoint
+
+enum Color
+{
+    Red,Green,Blue
+}
+
+RWStructuredBuffer<int> buffer;
+[numthreads(1, 1, 1)]
+void main(int id: SV_DispatchThreadID)
+{
+    if (id == Red)
+    {
+        buffer[0] = Green;
+    }
+    buffer[1] = Blue;
+}
-- 
cgit v1.2.3