AST: Fix crash on references to @cdecl enums at code generation

Add related end-to-end test.

Author: xymus

lib/AST/ClangTypeConverter.cpp

@@ -653,12 +653,13 @@ clang::QualType ClangTypeConverter::visitEnumType(EnumType *type) {
   if (type->isUninhabited())
     return convert(Context.TheEmptyTupleType);
 
-  if (!type->getDecl()->isObjC())
-    // Can't translate something not marked with @objc
+  auto ED = type->getDecl();
+  if (!ED->isObjC() && !ED->getAttrs().hasAttribute<CDeclAttr>())
+    // Can't translate something not marked with @objc or @cdecl.
     return clang::QualType();
 
   // @objc enums lower to their raw types.
-  return convert(type->getDecl()->getRawType());
+  return convert(ED->getRawType());
 }
 
 template <bool templateArgument>

test/Interpreter/cdecl_official_run.swift

@@ -0,0 +1,66 @@
+// RUN: %empty-directory(%t)
+// RUN: split-file %s %t --leading-lines
+
+/// Generate an internal cdecl.h
+// RUN: %target-swift-frontend(mock-sdk: %clang-importer-sdk) \
+// RUN:   %t/Lib.swift -emit-module -verify -o %t -emit-module-doc \
+// RUN:   -emit-clang-header-path %t/cdecl.h \
+// RUN:   -enable-experimental-feature CDecl
+
+/// Build and run a binary from Swift and C code.
+// RUN: %clang-no-modules -c %t/Client.c -o %t/Client.o \
+// RUN:   -I %t -I %clang-include-dir -Werror -isysroot %sdk
+// RUN: %target-build-swift %t/Lib.swift %t/Client.o -O -o %t/a.out \
+// RUN:   -enable-experimental-feature CDecl -parse-as-library
+// RUN: %target-codesign %t/a.out
+// RUN: %target-run %t/a.out > %t/run.log
+// RUN: %FileCheck %s --input-file %t/run.log
+
+// REQUIRES: swift_feature_CDecl
+// REQUIRES: executable_test
+
+//--- Lib.swift
+
+/// My documentation
+@cdecl(simple) public func simpleNameSwiftSide(x: CInt, bar y: CInt) -> CInt {
+    print(x, y)
+    return x
+}
+
+@cdecl func defaultName(x: Int) {
+    print(x)
+}
+
+@cdecl public func primitiveTypes(i: Int, ci: CInt, l: CLong, c: CChar, f: Float, d: Double, b: Bool) {
+    print(i, ci, l, c, f, d, b)
+}
+
+@cdecl enum CEnum: CInt { case A, B }
+
+@cdecl func useEnum(e: CEnum) -> CEnum {
+    print(e)
+    return e
+}
+
+//--- Client.c
+
+#include <stdio.h>
+#include "cdecl.h"
+
+int main() {
+    int x = simple(42, 43);
+    // CHECK: 42 43
+    printf("%d\n", x);
+    // CHECK-NEXT: 42
+
+    defaultName(121);
+    // CHECK-NEXT: 121
+
+    primitiveTypes(1, 2, 3, 'a', 1.0f, 2.0, true);
+    // CHECK-NEXT: 1 2 3 97 1.0 2.0 true
+
+    CEnum e = useEnum(CEnumB);
+    // CHECK-NEXT: B
+    printf("%d\n", e);
+    // CHECK-NEXT: 1
+}