Fix ConstantIntVal::toText when the val is a enum. (#6224)

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

* Fix comment.

Author: csyonghe

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.

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();
 }
 

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,

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)>