[cfe-commits] [PATCH] Add a warning for a function declaration that shadows a tag type

[Kaelyn Uhrain]

Hi,

This warning is to help make code like:

class Foo {
 public:
  enum Bar { X, Y };
  void SetBar(Bar bar);  // Setter
  Bar Bar()  // Getter
 private:
  Bar bar_;
};
void Foo::SetBar(Bar bar) { bar_ = bar; }
Foo::Bar Foo::Bar() { return bar_; }


be a bit easier to diagnose. Currently clang spits out a bunch of errors
without any real indication of what went wrong (the first error is the only
remotely helpful one, but it doesn't give any reason why an 'enum' tag has
to be added):

tmp.cc:7:3: error: must use 'enum' tag to refer to type 'Bar' in this scope
  Bar bar_;
  ^
  enum
tmp.cc:9:11: error: variable has incomplete type 'void'
void Foo::SetBar(Bar bar) { bar_ = bar; }
          ^
tmp.cc:9:18: error: use of undeclared identifier 'Bar'
void Foo::SetBar(Bar bar) { bar_ = bar; }
                 ^
tmp.cc:9:26: error: expected ';' after top level declarator
void Foo::SetBar(Bar bar) { bar_ = bar; }
                         ^
                         ;
4 errors generated.


With the patch, clang emits a warning before that cascade of errors:

tmp.cc:5:7: warning: function 'Bar' shadows enum 'Bar'; uses of enum 'Bar'
will require an 'enum'
      tag [-Wshadow]
  Bar Bar();  // Getter
      ^
tmp.cc:3:3: note: 'Bar' declared here
  enum Bar { X, Y };
  ^
tmp.cc:7:3: error: must use 'enum' tag to refer to type 'Bar' in this scope
<and the rest of the messages from the first output example>


I'm sending the patch for pre-commit review both because I'm uncertain
about the wording of the wording, and primarily because I'm not sure that
modifying Sema::ActOnStartFunctionDeclarator is the right place for the
check (though it was the best candidate I could find).

I'd also like to clean up the errors (in a separate patch) but the errors
seem to involve a lot of interactions between the parser and sema and may
take a while for me to figure out how to get things to work right. ;)

Cheers,
Kaelyn
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