[clang-tidy] Ignore singe bit bitfield -> bool conversion in readability-implicit-bool-conversion

llvm-svn: 343578

clang-tools-extra/clang-tidy/readability/ImplicitBoolConversionCheck.cpp

@@ -266,6 +266,7 @@ void ImplicitBoolConversionCheck::registerMatchers(MatchFinder *Finder) {
 
   auto exceptionCases =
       expr(anyOf(allOf(isMacroExpansion(), unless(isNULLMacroExpansion())),
+                 has(ignoringImplicit(memberExpr(hasDeclaration(fieldDecl(hasBitWidth(1)))))),
                  hasParent(explicitCastExpr())));
   auto implicitCastFromBool = implicitCastExpr(
       anyOf(hasCastKind(CK_IntegralCast), hasCastKind(CK_IntegralToFloating),

clang-tools-extra/docs/clang-tidy/checks/readability-implicit-bool-conversion.rst

@@ -66,7 +66,9 @@ example:
 
 In general, the following conversion types are checked:
 
-- integer expression/literal to boolean,
+- integer expression/literal to boolean (conversion from a single bit bitfield
+  to boolean is explicitly allowed, since there's no ambiguity / information
+  loss in this case),
 
 - floating expression/literal to boolean,
 

clang-tools-extra/test/clang-tidy/readability-implicit-bool-conversion.cpp

@@ -437,3 +437,24 @@ void useOfUserConversion() {
 }
 
 } // namespace ignoreUserDefinedConversionOperator
+
+namespace ignore_1bit_bitfields {
+
+struct S {
+  int a;
+  int b : 1;
+  int c : 2;
+};
+
+bool f(const S& s) {
+  functionTaking<bool>(s.a);
+  // CHECK-MESSAGES: :[[@LINE-1]]:24: warning: implicit conversion 'int' -> bool
+  // CHECK-FIXES: functionTaking<bool>(s.a != 0);
+  functionTaking<bool>(s.b);
+  // CHECK-FIXES: functionTaking<bool>(s.b);
+  functionTaking<bool>(s.c);
+  // CHECK-MESSAGES: :[[@LINE-1]]:24: warning: implicit conversion 'int' -> bool
+  // CHECK-FIXES: functionTaking<bool>(s.c != 0);
+}
+
+} // namespace ignore_1bit_bitfields