[clangd] Make FixIt message be consistent with the clang-tidy diagnostic message.

[hokein]

Summary

We strip the "[clang-tidy-check]" suffix from the clang-tidy diagnostics, we
should be consistent with the message in FixIt (strip the suffix as well).

clang-tools-extra/clangd/Diagnostics.cpp

if (Tidy != nullptr) {
           StringRef Rest(Msg);
           if (Rest.consume_back("]") && Rest.consume_back(Diag.Name) &&
               Rest.consume_back(" ["))
             Msg.resize(Rest.size());
         };
         CleanMessage(Diag.Message);
         for (auto &Note : Diag.Notes)
           CleanMessage(Note.Message);
+        for (auto &Fix : Diag.Fixes)
+          CleanMessage(Fix.Message);
         continue;
       }
     }
   }
   return std::move(Output);
 }
 
 void StoreDiags::BeginSourceFile(const LangOptions &Opts,

clang-tools-extra/clangd/unittests/DiagnosticsTests.cpp

 
 MATCHER_P3(Fix, Range, Replacement, Message,
            "Fix " + llvm::to_string(Range) + " => " +
                ::testing::PrintToString(Replacement) + " = [" + Message + "]") {
   return arg.Message == Message && arg.Edits.size() == 1 &&
          arg.Edits[0].range == Range && arg.Edits[0].newText == Replacement;
 }
 
+MATCHER_P(FixMessage, Message, "") {
+  return arg.Message == Message;
+}
+
 MATCHER_P(EqualToLSPDiag, LSPDiag,
           "LSP diagnostic " + llvm::to_string(LSPDiag)) {
   if (toJSON(arg) != toJSON(LSPDiag)) {
     *result_listener << llvm::formatv("expected:\n{0:2}\ngot\n{1:2}",
                                       toJSON(LSPDiag), toJSON(arg))
                             .str();
     return false;
   }
EXPECT_THAT(TU.build().getDiagnostics(),
                   DiagSource(Diag::Clang), DiagName("pp_file_not_found"))));
 }
 
 TEST(DiagnosticsTest, ClangTidy) {
   Annotations Test(R"cpp(
     #include $deprecated[["assert.h"]]
 
     #define $macrodef[[SQUARE]](X) (X)*(X)
-    int main() {
-      return $doubled[[sizeof]](sizeof(int));
-    }
-    int square() {
+    int $main[[main]]() {
       int y = 4;
       return SQUARE($macroarg[[++]]y);
+      return $doubled[[sizeof]](sizeof(int));
     }
   )cpp");
   auto TU = TestTU::withCode(Test.code());
   TU.HeaderFilename = "assert.h"; // Suppress "not found" error.
   TU.ClangTidyChecks =
       "-*, bugprone-sizeof-expression, bugprone-macro-repeated-side-effects, "
-      "modernize-deprecated-headers";
+      "modernize-deprecated-headers, modernize-use-trailing-return-type";
   EXPECT_THAT(
       TU.build().getDiagnostics(),
       UnorderedElementsAre(
           AllOf(Diag(Test.range("deprecated"),
                      "inclusion of deprecated C++ header 'assert.h'; consider "
                      "using 'cassert' instead"),
                 DiagSource(Diag::ClangTidy),
                 DiagName("modernize-deprecated-headers"),
                 WithFix(Fix(Test.range("deprecated"), "<cassert>",
                             "change '\"assert.h\"' to '<cassert>'"))),
           Diag(Test.range("doubled"),
                "suspicious usage of 'sizeof(sizeof(...))'"),
           AllOf(
               Diag(Test.range("macroarg"),
                    "side effects in the 1st macro argument 'X' are repeated in "
                    "macro expansion"),
               DiagSource(Diag::ClangTidy),
               DiagName("bugprone-macro-repeated-side-effects"),
               WithNote(
                   Diag(Test.range("macrodef"), "macro 'SQUARE' defined here"))),
           Diag(Test.range("macroarg"),
-               "multiple unsequenced modifications to 'y'")));
+               "multiple unsequenced modifications to 'y'"),
+          AllOf(
+            Diag(Test.range("main"),
+                 "use a trailing return type for this function"),
+            DiagSource(Diag::ClangTidy),
+            DiagName("modernize-use-trailing-return-type"),
+            // Verify that we don't have "[check-name]" suffix in the message.
+            WithFix(FixMessage("use a trailing return type for this function")))
+          ));
 }
 
 TEST(DiagnosticTest, ClangTidySuppressionComment) {
   Annotations Main(R"cpp(
     int main() {
       int i = 3;
       double d = 8 / i;  // NOLINT
       // NOLINTNEXTLINE