[PATCH] D52695: [clang][Parse] Diagnose useless null statements (PR39111)

[Roman Lebedev via Phabricator via cfe-commits]

lebedev.ri added inline comments.


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Comment at: lib/Parse/ParseStmt.cpp:237
+    SourceLocation SemiLocation = ConsumeToken();
+    if (!HasLeadingEmptyMacro && getCurScope()->isCompoundStmtScope() &&
+        !SemiLocation.isMacroID()) {
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rsmith wrote:
> I'm a little concerned that checking whether the scope is a compound statement isn't really checking the right thing -- what you care about is whether the syntactic context is a compound statement, not which scope a declaration at this level would be injected into. (Example of the difference: back in the pre-standard times when `{ for (int x = 0; x < 10; ++x) //...` injected `x` into the enclosing scope, the first substatement in that `for` statement would be in a compound-statement scope, but we definitely shouldn't warn on a stray `;` there.) If you moved this check into `ParseCompoundStatementBody`, there'd be no risk of such problems.
Great idea, thank you!
Testcases added, that fixed them.


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Comment at: test/Parser/extra-semi-resulting-in-nullstmt.cpp:59
+#if __cplusplus >= 201703L
+  if (; true) // OK
+    ;         // OK
----------------
rsmith wrote:
> It'd seem reasonable to warn on a null-statement as the *init-statement* of an `if` / `switch` / range-based `for`.
If you so insist :)


Repository:
  rC Clang

https://reviews.llvm.org/D52695