[clang-tidy] Don't use assignment for value-initialized enums

Summary:
The modernize-use-default-member-init check crashes when trying to
create an assignment value for a value-initialized enum because it isn't a
BuiltinType.
An enum cannot be initialized by assigning 0 to it unless a cast is added.
It could be initialized with an enumerator with the value 0, but there might not
be one.
Avoid these issues by ignoring the UseAssignment setting for value-initialized
enums.

Fixes PR35050.

Reviewers: aaron.ballman, alexfh, JonasToth

Reviewed By: JonasToth

Subscribers: xazax.hun, cfe-commits

Tags: #clang

Differential Revision: https://reviews.llvm.org/D57852

llvm-svn: 353554

1 files changed, 8 insertions, 0 deletions

diff --git a/clang-tools-extra/test/clang-tidy/modernize-use-default-member-init.cpp b/clang-tools-extra/test/clang-tidy/modernize-use-default-member-init.cpp
index d35ad330c56..825bfa0bfbe 100644
--- a/clang-tools-extra/test/clang-tidy/modernize-use-default-member-init.cpp
+++ b/clang-tools-extra/test/clang-tidy/modernize-use-default-member-init.cpp
@@ -165,6 +165,14 @@ struct PositiveEnum {
   // CHECK-FIXES: Enum e{Foo};
 };
 
+struct PositiveValueEnum {
+  PositiveValueEnum() : e() {}
+  // CHECK-FIXES: PositiveValueEnum()  {}
+  Enum e;
+  // CHECK-MESSAGES: :[[@LINE-1]]:8: warning: use default member initializer for 'e'
+  // CHECK-FIXES: Enum e{};
+};
+
 struct PositiveString {
   PositiveString() : s("foo") {}
   // CHECK-FIXES: PositiveString()  {}