[clang-tidy] Tweak misc-static-assert fix in c++17

[njames93]

Summary

If C++17 mode is enabled and the assert doesn't have a string literal, we can emit a static assert with no message in favour of one with an empty message.

[njames93]

clang-tools-extra/test/clang-tidy/checkers/misc-static-assert.cpp

41–43

This seems to be a shortfall in check_clang_tidy.py. It will pass CHECK-MESSAGES-CXX(11|17) as a prefix to file check even though it knows it wasn't in the source file. This causes filecheck to fail.
Duplicating the CHECK-MESSAGE for each is just a work around.

[aaron.ballman]

LGTM!

clang-tools-extra/clang-tidy/misc/StaticAssertCheck.cpp

void StaticAssertCheck::check(const MatchFinder::MatchResult &Result) {
 
   SmallVector<FixItHint, 4> FixItHints;
   SourceLocation LastParenLoc;
   if (AssertLoc.isValid() && !AssertLoc.isMacroID() &&
       (LastParenLoc = getLastParenLoc(ASTCtx, AssertLoc)).isValid()) {
     FixItHints.push_back(
         FixItHint::CreateReplacement(SourceRange(AssertLoc), "static_assert"));
 
-    std::string StaticAssertMSG = ", \"\"";
     if (AssertExprRoot) {
       FixItHints.push_back(FixItHint::CreateRemoval(
           SourceRange(AssertExprRoot->getOperatorLoc())));
       FixItHints.push_back(FixItHint::CreateRemoval(
           SourceRange(AssertMSG->getBeginLoc(), AssertMSG->getEndLoc())));
-      StaticAssertMSG = (Twine(", \"") + AssertMSG->getString() + "\"").str();
+      FixItHints.push_back(FixItHint::CreateInsertion(
+          LastParenLoc, (Twine(", \"") + AssertMSG->getString() + "\"").str()));
+    } else if (!Opts.CPlusPlus17) {
+      FixItHints.push_back(FixItHint::CreateInsertion(LastParenLoc, ", \"\""));
     }
-
-    FixItHints.push_back(
-        FixItHint::CreateInsertion(LastParenLoc, StaticAssertMSG));
   }
 
   diag(AssertLoc, "found assert() that could be replaced by static_assert()")
       << FixItHints;
 }
 
 SourceLocation StaticAssertCheck::getLastParenLoc(const ASTContext *ASTCtx,
                                                   SourceLocation AssertLoc) {

clang-tools-extra/test/clang-tidy/checkers/misc-static-assert.cpp

-// RUN: %check_clang_tidy %s misc-static-assert %t
+// RUN: %check_clang_tidy -std=c++11 -check-suffixes=,CXX11 %s misc-static-assert %t
+// RUN: %check_clang_tidy -std=c++17 -check-suffixes=,CXX17 %s misc-static-assert %t
 
 void abort() {}
 #ifdef NDEBUG
 #define assert(x) 1
 #else
 #define assert(x)                                                              \
   if (!(x))                                                                    \
   abort()

 class B {
 public:
   constexpr bool method() { return true; }
 };
 
 template <class T> void doSomething(T t) {
   assert(myfunc(1, 2));
   // CHECK-MESSAGES: :[[@LINE-1]]:3: warning: found assert() that could be replaced by static_assert() [misc-static-assert]
-  // CHECK-FIXES: {{^  }}static_assert(myfunc(1, 2), "");
+  // CHECK-FIXES-CXX11: {{^  }}static_assert(myfunc(1, 2), "");
+  // CHECK-FIXES-CXX17: {{^  }}static_assert(myfunc(1, 2));
 
   assert(t.method());
   // CHECK-FIXES: {{^  }}assert(t.method());
 
   assert(sizeof(T) == 123);
 }
 
 int main() {
   my_macro();
   // CHECK-MESSAGES: :[[@LINE-1]]:3: warning: found assert() that could be
   // CHECK-FIXES: {{^  }}my_macro();
 
   assert(myfunc(1, 2) && (3 == 4));
   // CHECK-MESSAGES: :[[@LINE-1]]:3: warning: found assert() that could be
-  // CHECK-FIXES: {{^  }}static_assert(myfunc(1, 2) && (3 == 4), "");
+  // CHECK-FIXES-CXX11: {{^  }}static_assert(myfunc(1, 2) && (3 == 4), "");
+  // CHECK-FIXES-CXX17: {{^  }}static_assert(myfunc(1, 2) && (3 == 4));
 
   int x = 1;
   assert(x == 0);
   // CHECK-FIXES: {{^  }}assert(x == 0);
 
   A a;
   B b;
 
   doSomething<A>(a);
   doSomething<B>(b);
 
   assert(false);
   // CHECK-FIXES: {{^  }}assert(false);
 
   assert(False);
   // CHECK-FIXES: {{^  }}assert(False);
   assert(FALSE);
   // CHECK-FIXES: {{^  }}assert(FALSE);
 
   assert(ZERO_MACRO);
   // CHECK-MESSAGES: :[[@LINE-1]]:3: warning: found assert() that could be
-  // CHECK-FIXES: {{^  }}static_assert(ZERO_MACRO, "");
+  // CHECK-FIXES-CXX11: {{^  }}static_assert(ZERO_MACRO, "");
+  // CHECK-FIXES-CXX17: {{^  }}static_assert(ZERO_MACRO);
 
   assert(!"Don't report me!");
   // CHECK-FIXES: {{^  }}assert(!"Don't report me!");
 
   assert(0 && "Don't report me!");
   // CHECK-FIXES: {{^  }}assert(0 && "Don't report me!");
 
   assert(false && "Don't report me!");
#undef false
   // CHECK-FIXES: {{^  }}assert(strlen("12345") == 5);
 
 #define assert(e) (__builtin_expect(!(e), 0) ? print (#e, __FILE__, __LINE__) : (void)0)
   assert(false);
   // CHECK-FIXES: {{^  }}assert(false);
 
   assert(10 == 5 + 5);
   // CHECK-MESSAGES: :[[@LINE-1]]:3: warning: found assert() that could be
-  // CHECK-FIXES: {{^  }}static_assert(10 == 5 + 5, "");
+  // CHECK-FIXES-CXX11: {{^  }}static_assert(10 == 5 + 5, "");
+  // CHECK-FIXES-CXX17: {{^  }}static_assert(10 == 5 + 5);
 #undef assert
 
   return 0;
 }