[cfe-dev] [clang-tidy] problem finding AST matcher for nested implicit const-cast

[Don Hinton via cfe-dev]

Hi Torbjörn:

This behavior appears to be intentional, though it would be friendly to
emit a warning.  I believe this is the case your are hitting:

   794      } else if (!Context->hasSameType(CanonicalInitVarType,
   795                                       CanonicalBeginType)) {
   796        // Check for qualified types to avoid conversions from
non-const to const
   797        // iterator types.
   798        return false;
   799      }

hth...
don

On Tue, May 7, 2019 at 1:06 PM Torbjörn Klatt via cfe-dev <
cfe-dev at lists.llvm.org> wrote:

> Hi all,
>
> I'm trying to fix the clang-tidy bug 35082 [1] as a starter for getting
> into LLVM development and contribution.
>
> I think, I've tracked down the issue to
>
> clang-tidy/modernize/LoopConvertCheck.cpp:123ff:
> clang::tidy::modernize::makeIteratorLoopMatcher()
> ```
>   DeclarationMatcher InitDeclMatcher =
>       varDecl(hasInitializer(anyOf(ignoringParenImpCasts(BeginCallMatcher),
>                                    materializeTemporaryExpr(
>
>  ignoringParenImpCasts(BeginCallMatcher)),
>                                    hasDescendant(BeginCallMatcher))))
>           .bind(InitVarName);
> ```
> The definition of `InitDeclMatcher` seems to not match  the AST tree
> ```
>   |-ForStmt
>   | |-DeclStmt
>   | | `-VarDecl
>   | |   `-ExprWithCleanups
>   | |     `-ImplicitCastExpr
>   | |       `-CXXConstructExpr
>   | |         `-MaterializeTemporaryExpr
>   | |           `-ImplicitCastExpr
>   | |             `-CXXMemberCallExpr
>   | |               `-MemberExpr
>   | |                 `-DeclRefExpr
> ```
> of
> ```
> std::vector<int> vec{1, 2, 3, 4, 5};
> for(std::vector<int>::const_iterator i = vec.begin(); i != vec.end(); ++i)
> { ... }
> ```
>
> In my naivety, I tried to include the following into the `anyOf`:
> ```
>                                    exprWithCleanups(
>                                        ignoringParenImpCasts(
>                                            cxxConstructExpr(
>                                                materializeTemporaryExpr(
>                                                    ignoringParenImpCasts(
>
>  BeginCallMatcher))))),
> ```
> mimicking the specific AST tree. Without luck.
>
> I browsed through include/clang/ASTMatchers.h for better suited matchers,
> but couldn't find any.
>
> What important detail am I missing?
>
> Best
> Torbjörn
>
> [1]: https://bugs.llvm.org/show_bug.cgi?id=35082
>
>
>
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