Fix Bugzilla Issue 24504 - ImportC: Enum declarations with a mixture of int and uint literal values cause errors, when targeting Windows, when debug info generation is enabled. (#16385)

compiler/src/dmd/enumsem.d

@@ -325,7 +325,10 @@ void enumSemantic(Scope* sc, EnumDeclaration ed)
                 if (EnumMember em = s.isEnumMember())
                 {
                     em.type = commonType;
-                    em.value = em.value.castTo(sc, commonType);
+                    // optimize out the cast so that other parts of the compiler can
+                    // assume that an integral enum's members are `IntegerExp`s.
+                    // https://issues.dlang.org/show_bug.cgi?id=24504
+                    em.value = em.value.castTo(sc, commonType).optimize(WANTvalue);
                 }
             });
         }

compiler/test/compilable/test24504.c

@@ -0,0 +1,10 @@
+// REQUIRED_ARGS: -os=windows -g
+// DISABLED: osx
+// This is disabled on macOS because ld complains about _main being undefined
+// when clang attempts to preprocess the C file.
+
+typedef enum
+{
+    HasIntAndUIntValuesInt = 0,
+    HasIntAndUIntValuesUInt = 0x80000000
+} HasIntAndUIntValues;