[Diagnostic] make Wmisleading-indendation not warn about labels

[aaron.ballman]

clang/lib/Parse/ParseStmt.cpp

1278–1279

Can this be triggered by other forms of syntax than labels? e.g.,

for ( auto
a :
whatever) {}

struct S {
int
a:
1
};

// or, with contract attributes
[[
pre :
true]]

[Tyker]

clang/lib/Parse/ParseStmt.cpp

1278–1279

none of them are valid beginning of statements so they won't occur here. and worse case this will only disable the warning.

[aaron.ballman]

LGTM!

clang/lib/Parse/ParseStmt.cpp

1278–1279

Fantastic, thank you for confirming!

clang/lib/Parse/ParseStmt.cpp

void Check() {
 
     SourceManager &SM = P.getPreprocessor().getSourceManager();
     unsigned PrevColNum = getVisualIndentation(SM, PrevLoc);
     unsigned CurColNum = getVisualIndentation(SM, Tok.getLocation());
     unsigned StmtColNum = getVisualIndentation(SM, StmtLoc);
 
     if (PrevColNum != 0 && CurColNum != 0 && StmtColNum != 0 &&
         ((PrevColNum > StmtColNum && PrevColNum == CurColNum) ||
-         !Tok.isAtStartOfLine()) && SM.getPresumedLineNumber(StmtLoc) !=
-          SM.getPresumedLineNumber(Tok.getLocation())) {
-      P.Diag(Tok.getLocation(), diag::warn_misleading_indentation)
-          << Kind;
+         !Tok.isAtStartOfLine()) &&
+        SM.getPresumedLineNumber(StmtLoc) !=
+            SM.getPresumedLineNumber(Tok.getLocation()) &&
+        (Tok.isNot(tok::identifier) ||
+         P.getPreprocessor().LookAhead(0).isNot(tok::colon))) {
+      P.Diag(Tok.getLocation(), diag::warn_misleading_indentation) << Kind;
       P.Diag(StmtLoc, diag::note_previous_statement);
     }
   }
 };
 
 }
 
 /// ParseIfStatement

clang/test/Parser/warn-misleading-indentation.cpp

if (1) goto fail; goto fail;
     if (0)
         FOO;
 
     goto fail;
 
 fail:;
 }
 
+void f_label(int b) {
+  if (b)
+    return;
+    a:
+  return;
+  goto a;
+}