Add IREnumType to distinguish enums from ints and each other (#6973)

* Add IREnumType to distinguish enums from ints and each other

* Add issue example as test

* format code

* Add expected test output

* Fix peephole optimization hanging

No idea why this PR triggered this, but there seems to have been a clear bug
here anyway, so may just as well fix it now.

* Move enum lowering later

* Add linkage decoration to enum type

* Use filecheck-buffer instead of expected.txt

* Fix comment

* Make enum casts actually use IR enum casts

They were all BuiltinCasts by accident

* Lower enum type before VM

* Deal with rate-qualified types in enum cast

* Allow any value marshalling for enum types

* Handle new enum instructions in a couple more switches

* Fix formatting

---------

Co-authored-by: slangbot <186143334+slangbot@users.noreply.github.com>

1 files changed, 3 insertions, 6 deletions

diff --git a/source/slang/slang-lower-to-ir.cpp b/source/slang/slang-lower-to-ir.cpp
index 990090537..45efca2d9 100644
--- a/source/slang/slang-lower-to-ir.cpp
+++ b/source/slang/slang-lower-to-ir.cpp
@@ -9228,18 +9228,15 @@ struct DeclLoweringVisitor : DeclVisitor<DeclLoweringVisitor, LoweredValInfo>
         auto subContext = nestedContext.getContext();
         auto outerGeneric = emitOuterGenerics(subContext, decl, decl);
 
-        // An `enum` declaration will currently lower directly to its "tag"
-        // type, so that any references to the `enum` become referenes to
-        // the tag type instead.
-        //
         // TODO: if we ever support `enum` types with payloads, we would
         // need to make the `enum` lower to some kind of custom "tagged union"
         // type.
 
         IRType* loweredTagType = lowerType(subContext, decl->tagType);
+        IRType* enumType = subBuilder->createEnumType(loweredTagType);
+        addLinkageDecoration(context, enumType, decl);
 
-        return LoweredValInfo::simple(
-            finishOuterGenerics(subBuilder, loweredTagType, outerGeneric));
+        return LoweredValInfo::simple(finishOuterGenerics(subBuilder, enumType, outerGeneric));
     }
 
     LoweredValInfo visitThisTypeDecl(ThisTypeDecl* decl)