[ClangImporter] Fix importing values for constant globals of enum types

Author: kubamracek

lib/ClangImporter/ImportDecl.cpp

@@ -4583,7 +4583,7 @@ namespace {
       if (dc->isTypeContext())
         isStatic = true;
 
-      // For now we don't import static constexpr
+      // For now we don't import static constexpr. TODO: Lift this restriction.
       if (isStatic && decl->isConstexpr())
         return nullptr;
 
@@ -4606,8 +4606,13 @@ namespace {
               decl->getType(), ImportTypeKind::Value,
               ImportDiagnosticAdder(Impl, decl, decl->getLocation()),
               isInSystemModule(dc), Bridgeability::None, ImportTypeAttrs());
+
+          auto convertKind = ConstantConvertKind::None;
+          if (decl->getType()->isEnumeralType())
+            convertKind = ConstantConvertKind::Construction;
+
           result = synthesizer.createConstant(
-              name, dc, type, *val, ConstantConvertKind::None, isStatic, decl,
+              name, dc, type, *val, convertKind, isStatic, decl,
               importer::convertClangAccess(decl->getAccess()));
         }
       }

test/ClangImporter/const_values.swift

@@ -28,7 +28,6 @@ typedef enum MyEnum: char {
 } MyEnum;
 static const MyEnum static_const_enum = MyEnumCase1;
 
-
 //--- main.swift
 func foo() {
   print(MACRO_INT)
@@ -110,4 +109,10 @@ func foo() {
 // CHECK-NEXT:   return %1
 // CHECK-NEXT: }
 
-// TODO: Add static_const_enum
+// CHECK:      sil shared [transparent] @$sSo17static_const_enumSo6MyEnumVvg : $@convention(thin) () -> MyEnum {
+// CHECK-NEXT: bb0:
+// CHECK-NEXT:   %0 = integer_literal $Builtin.Int8, 1
+// CHECK-NEXT:   %1 = struct $Int8 (%0)
+// CHECK-NEXT:   %2 = struct $MyEnum (%1)
+// CHECK-NEXT:   return %2
+// CHECK-NEXT: }