[PATCH] Suggest fix-it ':' when '=' used in for-range-declaration while initializing an auto

[Richard Smith]

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Comment at: include/clang/Basic/DiagnosticParseKinds.td:207
@@ -206,1 +206,3 @@
 def err_expected_semi_for : Error<"expected ';' in 'for' statement specifier">;
+def warn_single_decl_assign_in_for_range : Warning<
+  "range based for statement requires ':' after range declaration">,
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This should be an `ExtWarn` or (strongly preferably) just an `Error`. I don't see any good reason to support this as an extension.

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Comment at: include/clang/Parse/Parser.h:1728
@@ -1727,1 +1727,3 @@
+      const ParsedTemplateInfo &TemplateInfo = ParsedTemplateInfo(),
+      bool IsFirstDeclInGroup = false);
   bool ParseAsmAttributesAfterDeclarator(Declarator &D);
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You don't need this new flag. Use `Declarator::isFirstDeclarator` instead.

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Comment at: lib/Parse/ParseDecl.cpp:1830
@@ +1829,3 @@
+      if (Tok.is(tok::r_paren) && getLangOpts().CPlusPlus11 &&
+          D.getContext() == Declarator::ForContext && TypeContainsAuto &&
+          IsFirstDeclInGroup) {
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Why check `TypeContainsAuto`? I don't think that's a good indicator either way.

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Comment at: lib/Parse/ParseDecl.cpp:1832-1833
@@ +1831,4 @@
+          IsFirstDeclInGroup) {
+        Diag(EqualLoc, diag::warn_single_decl_assign_in_for_range)
+            << FixItHint::CreateReplacement(EqualLoc, ":");
+      }
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Please try to avoid follow-on errors here. After giving your error message, perhaps mark `Init` as invalid, and make sure that the rest of the parsing code handles this without producing spurious diagnostics.

http://reviews.llvm.org/D3370