From 2ae194d51e15c064c3d905e628f7335de7504e32 Mon Sep 17 00:00:00 2001
From: Yong He <yonghe@outlook.com>
Date: Wed, 29 Jan 2025 23:11:06 -0800
Subject: Fix ConstantIntVal::toText when the val is a enum. (#6224)

* Fix ConstantIntVal::toText when the val is a enum.

* Fix comment.
---
 source/slang/slang-ast-decl.h                    |  2 ++
 source/slang/slang-ast-val.cpp                   | 24 ++++++++++++++++++++++++
 source/slang/slang-check-decl.cpp                |  5 ++---
 tests/language-server/typename-enum-intval.slang | 24 ++++++++++++++++++++++++
 4 files changed, 52 insertions(+), 3 deletions(-)
 create mode 100644 tests/language-server/typename-enum-intval.slang

diff --git a/source/slang/slang-ast-decl.h b/source/slang/slang-ast-decl.h
index 81e7337c7..7feb70e6a 100644
--- a/source/slang/slang-ast-decl.h
+++ b/source/slang/slang-ast-decl.h
@@ -210,6 +210,8 @@ class EnumCaseDecl : public Decl
 
     // Tag value
     Expr* tagExpr = nullptr;
+
+    IntVal* tagVal = nullptr;
 };
 
 // A member of InterfaceDecl representing the abstract ThisType.
diff --git a/source/slang/slang-ast-val.cpp b/source/slang/slang-ast-val.cpp
index 98135ef16..9bcfd21bc 100644
--- a/source/slang/slang-ast-val.cpp
+++ b/source/slang/slang-ast-val.cpp
@@ -149,6 +149,30 @@ void Val::_toTextOverride(StringBuilder& out)
 
 void ConstantIntVal::_toTextOverride(StringBuilder& out)
 {
+    if (auto enumTypeDecl = isDeclRefTypeOf<EnumDecl>(getType()))
+    {
+        // If this is an enum type, then we want to print the name of the
+        // corresponding enum case, instead of the raw integer value, if possible.
+        //
+        // We will look up the enum case that corresponds to the value, and
+        // print its name if we can find one.
+        //
+        for (auto enumCase : enumTypeDecl.getDecl()->getMembersOfType<EnumCaseDecl>())
+        {
+            if (auto constVal = as<ConstantIntVal>(enumCase->tagVal))
+            {
+                if (constVal->getValue() == getValue())
+                {
+                    out << DeclRef(enumCase);
+                    return;
+                }
+            }
+        }
+
+        // Fallback to explicit cast to the enum type.
+        out << getType() << "(" << getValue() << ")";
+        return;
+    }
     out << getValue();
 }
 
diff --git a/source/slang/slang-check-decl.cpp b/source/slang/slang-check-decl.cpp
index d12374d52..7d083e53b 100644
--- a/source/slang/slang-check-decl.cpp
+++ b/source/slang/slang-check-decl.cpp
@@ -7967,9 +7967,8 @@ void SemanticsDeclBodyVisitor::visitEnumCaseDecl(EnumCaseDecl* decl)
         initExpr = coerce(CoercionSite::General, tagType, initExpr);
 
         // We want to enforce that this is an integer constant
-        // expression, but we don't actually care to retain
-        // the value.
-        CheckIntegerConstantExpression(
+        // expression.
+        decl->tagVal = CheckIntegerConstantExpression(
             initExpr,
             IntegerConstantExpressionCoercionType::AnyInteger,
             nullptr,
diff --git a/tests/language-server/typename-enum-intval.slang b/tests/language-server/typename-enum-intval.slang
new file mode 100644
index 000000000..9eca71ae2
--- /dev/null
+++ b/tests/language-server/typename-enum-intval.slang
@@ -0,0 +1,24 @@
+//TEST:LANG_SERVER(filecheck=CHECK):
+
+namespace ns {
+enum Test : uint32_t
+{
+    A = 1,
+    B = 2,
+}
+
+struct Foo<let T : Test>
+{
+}
+}
+
+void f()
+{
+//HOVER:18,25
+    ns.Foo<ns.Test.A> first;
+//HOVER:20,27
+    ns.Foo<ns.Test(3)> second;
+}
+
+// CHECK: ns.Foo<ns.Test.A>
+// CHECK: ns.Foo<ns.Test(3)>
\ No newline at end of file
-- 
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