r194002 - Try to correct a mistyped "-" or ">" to "->" for some C++ cases.

[Kaelyn Uhrain]

On Mon, Nov 4, 2013 at 6:37 PM, Richard Smith <richard at metafoo.co.uk> wrote:

>
> On 4 Nov 2013 11:05, "Kaelyn Uhrain" <rikka at google.com> wrote:
> >
> > Author: rikka
> > Date: Mon Nov  4 12:59:34 2013
> > New Revision: 194002
> >
> > URL: http://llvm.org/viewvc/llvm-project?rev=194002&view=rev
> > Log:
> > Try to correct a mistyped "-" or ">" to "->" for some C++ cases.
> >
> > Similar C code isn't caught as it seems to hit a different code path.
> > Also, as the check is only done for record pointers, cases involving
> > an overloaded operator-> are not handled either. Note that the reason
> > this check is done in the parser instead of Sema is not related to
> > having enough knowledge about the current state as it is about being
> > able to fix up the parser's state to be able to recover and traverse the
> > correct code paths.
> >
> > Modified:
> >     cfe/trunk/include/clang/Basic/DiagnosticParseKinds.td
> >     cfe/trunk/lib/Parse/ParseExpr.cpp
> >     cfe/trunk/test/SemaCXX/member-expr.cpp
> >
> > Modified: cfe/trunk/include/clang/Basic/DiagnosticParseKinds.td
> > URL:
> http://llvm.org/viewvc/llvm-project/cfe/trunk/include/clang/Basic/DiagnosticParseKinds.td?rev=194002&r1=194001&r2=194002&view=diff
> >
> ==============================================================================
> > --- cfe/trunk/include/clang/Basic/DiagnosticParseKinds.td (original)
> > +++ cfe/trunk/include/clang/Basic/DiagnosticParseKinds.td Mon Nov  4
> 12:59:34 2013
> > @@ -499,6 +499,9 @@ def ext_abstract_pack_declarator_parens
> >  def err_function_is_not_record : Error<
> >    "unexpected '%select{.|->}0' in function call; perhaps remove the "
> >    "'%select{.|->}0'?">;
> > +def err_mistyped_arrow_in_member_access : Error<
> > +  "use of undeclared identifier %0; did you mean '->' instead of "
> > +  "'%select{-|>}1'?">;
> >
> >  // C++ derived classes
> >  def err_dup_virtual : Error<"duplicate 'virtual' in base specifier">;
> >
> > Modified: cfe/trunk/lib/Parse/ParseExpr.cpp
> > URL:
> http://llvm.org/viewvc/llvm-project/cfe/trunk/lib/Parse/ParseExpr.cpp?rev=194002&r1=194001&r2=194002&view=diff
> >
> ==============================================================================
> > --- cfe/trunk/lib/Parse/ParseExpr.cpp (original)
> > +++ cfe/trunk/lib/Parse/ParseExpr.cpp Mon Nov  4 12:59:34 2013
> > @@ -166,6 +166,46 @@ ExprResult Parser::ParseAssignmentExpres
> >    ExprResult LHS = ParseCastExpression(/*isUnaryExpression=*/false,
> >                                         /*isAddressOfOperand=*/false,
> >                                         isTypeCast);
> > +
> > +  // Check for a possible typo of "-" or ">" instead of "->" after a
> > +  // pointer to a struct or class, while recovery is still possible.
> > +  if (LHS.isUsable() && (Tok.is(tok::minus) || Tok.is(tok::greater))) {
> > +    QualType LHSType = LHS.get()->getType();
> > +    const RecordType *Pointee =
> > +        LHSType->isPointerType()
> > +            ? LHSType->getPointeeType()->getAsStructureType()
> > +            : 0;
> > +    const RecordDecl *RD = Pointee ? Pointee->getDecl() : 0;
> > +    const Token &NextTok = NextToken();
> > +    if (RD && NextTok.is(tok::identifier)) {
> > +      UnqualifiedId Name;
> > +      CXXScopeSpec ScopeSpec;
> > +      SourceLocation TemplateKWLoc;
> > +      NoTypoCorrectionCCC NoTCValidator;
> > +      Name.setIdentifier(NextTok.getIdentifierInfo(),
> NextTok.getLocation());
> > +      Sema::SFINAETrap Trap(Actions);
> > +      ExprResult Res =
> > +          Actions.ActOnIdExpression(getCurScope(), ScopeSpec,
> TemplateKWLoc,
> > +                                    Name, false, false, &NoTCValidator);
> > +      if (Res.isInvalid()) {
>
> What happens if the next token is ( or :: or similar, and this identifier
> is not an id-expression by itself? For instance, p-f(x) might find f by adl.
>
Assuming (1) "f" is both the name of a member of "p" and something not
found through a simple lookup but through adl or similar, and (2) the
pointer arithmetic/comparison on an object pointer is intended, then yes
this will probably do the wrong thing. And while it's not great, working
around that should be pretty trivial (e.g. adding parentheses around the
rhs of the "-" or ">").

> Also, in the case where this succeeds, we should annotate the produced
> expression onto the token stream to avoid reparsing it later.
>
I'm not sure what you're saying here... care to explain?

> > +        Token OpTok = Tok;
> > +        Tok.setKind(tok::arrow);
> > +        PP.EnableBacktrackAtThisPos();
> > +        Res = ParsePostfixExpressionSuffix(LHS);
> > +        if (Res.isUsable()) {
> > +          LHS = Res;
> > +          PP.CommitBacktrackedTokens();
> > +          Diag(OpTok, diag::err_mistyped_arrow_in_member_access)
> > +              << NextTok.getIdentifierInfo() << OpTok.is(tok::greater)
> > +              << FixItHint::CreateReplacement(OpTok.getLocation(),
> "->");
> > +        } else {
> > +          Tok = OpTok;
> > +          PP.Backtrack();
> > +        }
> > +      }
> > +    }
> > +  }
> > +
> >    return ParseRHSOfBinaryExpression(LHS, prec::Assignment);
> >  }
> >
> >
> > Modified: cfe/trunk/test/SemaCXX/member-expr.cpp
> > URL:
> http://llvm.org/viewvc/llvm-project/cfe/trunk/test/SemaCXX/member-expr.cpp?rev=194002&r1=194001&r2=194002&view=diff
> >
> ==============================================================================
> > --- cfe/trunk/test/SemaCXX/member-expr.cpp (original)
> > +++ cfe/trunk/test/SemaCXX/member-expr.cpp Mon Nov  4 12:59:34 2013
> > @@ -224,3 +224,16 @@ namespace pr16676 {
> >          .i;  // expected-error {{member reference type 'pr16676::S *'
> is a pointer; maybe you meant to use '->'}}
> >    }
> >  }
> > +
> > +namespace PR9054 {
> > +struct Foo {
> > +  void bar(int);
> > +  int fiz;
> > +};
> > +
> > +int test(struct Foo *foo) {
> > +  foo-bar(5);  // expected-error {{use of undeclared identifier 'bar';
> did you mean '->' instead of '-'?}}
> > +  foo>baz(4);  // expected-error-re {{use of undeclared identifier
> 'baz'$}}
> > +  return foo>fiz;  // expected-error {{use of undeclared identifier
> 'fiz'; did you mean '->' instead of '>'?}}
> > +}
> > +}
> >
> >
> > _______________________________________________
> > cfe-commits mailing list
> > cfe-commits at cs.uiuc.edu
> > http://lists.cs.uiuc.edu/mailman/listinfo/cfe-commits
>
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