[Diagnsotics] Small Improvement on -Wmisleading-indentation

[xbolva00]

clang/lib/Parse/ParseStmt.cpp

1221–1223

DiagnosticsEngine‘s isIgnored?

[aaron.ballman]

clang/lib/Parse/ParseStmt.cpp

1221

Rather than querying the diagnostics engine for each call to Check(), I think you can query this property once in the constructor and then do a simple member variable test here instead.

1231–1232

Under what circumstances is this required (can we generate a test case for it)?

[Tyker]

clang/lib/Parse/ParseStmt.cpp

1221

Check() is called only once per object so there should be no difference. and DiagnosticsEngine::isIgnored requests the location of the location at which the warning is supposed to appear. this location is not know during the construction of the object.

1231–1232

i managed to reproduced it https://godbolt.org/z/XqVNPD

[aaron.ballman]

LGTM

clang/lib/Parse/ParseStmt.cpp

1221

Okay, sounds good

clang/lib/Parse/ParseStmt.cpp

if (!P.MisleadingIndentationElseLoc.isInvalid()) {
       P.MisleadingIndentationElseLoc = SourceLocation();
     }
     if (Kind == MSK_else && !ShouldSkip)
       P.MisleadingIndentationElseLoc = SL;
   }
   void Check() {
     NeedsChecking = false;
     Token Tok = P.getCurToken();
-    if (ShouldSkip || NumDirectives != P.getPreprocessor().getNumDirectives() ||
+    if (P.getActions().getDiagnostics().isIgnored(
+            diag::warn_misleading_indentation, Tok.getLocation()) ||
+        ShouldSkip || NumDirectives != P.getPreprocessor().getNumDirectives() ||
         Tok.isOneOf(tok::semi, tok::r_brace) || Tok.isAnnotation() ||
         Tok.getLocation().isMacroID() || PrevLoc.isMacroID() ||
         StmtLoc.isMacroID() ||
         (Kind == MSK_else && P.MisleadingIndentationElseLoc.isInvalid())) {
       P.MisleadingIndentationElseLoc = SourceLocation();
       return;
     }
+    if (Kind == MSK_else)
+      P.MisleadingIndentationElseLoc = SourceLocation();
 
     SourceManager &SM = P.getPreprocessor().getSourceManager();
     unsigned PrevColNum = SM.getSpellingColumnNumber(PrevLoc);
     unsigned CurColNum = SM.getSpellingColumnNumber(Tok.getLocation());
     unsigned StmtColNum = SM.getSpellingColumnNumber(StmtLoc);
 
     if (PrevColNum != 0 && CurColNum != 0 && StmtColNum != 0 &&
         ((PrevColNum > StmtColNum && PrevColNum == CurColNum) ||