Fix #13847 (simplifyTypedef should not simplify all using statements)

[danmar]

No description provided.

[chrchr-github]

Do we handle this code?

namespace x {
    struct a{};
}

int main() {
    int a = 0;
    using x::a;
    return a + 2;
}

FYI accepted by clang and gcc, rejected by msvc.

[danmar]

Do we handle this code?

I thought it would.. do I understand it correctly that the using x::a should be ignored..

[chrchr-github]

Do we handle this code?

I thought it would.. do I understand it correctly that the using x::a should be ignored..

Yes, at least two compilers interpret a as a variable.

[danmar]

After simplifyTypedef the tokens are now:

1: namespace x {
2: struct a { } ;
3: }
4:
5: int main ( ) {
6: int a ; a = 0 ;
7: using x :: a ;
8: return a + 2 ;
9: }

And then after this the simplifyUsing is called which transforms the code to:

1: namespace x {
2: struct a { } ;
3: }
4:
5: int main ( ) {
6: int a ; a = 0 ;
7:
8: return x :: a + 2 ;
9: }

[danmar]

I feel I would rather not update simplifyUsing also in this PR.

But if I move the variable a little then clang suddenly seems to reject the code:

namespace x {
    struct a{};
}

int main() {
    int a = 0;
    {
      using x::a;
      return a + 2;
    }
}

so it seems if we make some exception in simplifyUsing it should only be for the variables in local scope

[Copilot]

Pull Request Overview

This PR addresses issue #13847 by preventing the simplifyTypedef pass from converting all using statements into typedefs in C++ code.

• Added a new tokenizer test (tokenize41) to cover the no-simplify-using scenario.
• Introduced typedefInfo3 to verify that dumpTypedefInfo ignores using statements.
• Removed the old simplifyUsingToTypedef method and inlined minimal using→typedef logic into simplifyTypedefCpp.

Reviewed Changes

Copilot reviewed 4 out of 4 changed files in this pull request and generated no comments.

File	Description
test/testtokenize.cpp	Added tokenize41 test for using statements (#13847).
test/testsimplifytypedef.cpp	Registered new typedefInfo3 test; removed typedefInfo2 registration.
lib/tokenize.h	Dropped simplifyUsingToTypedef declaration.
lib/tokenize.cpp	Removed simplifyUsingToTypedef implementation; inlined simple using→typedef pattern.

Comments suppressed due to low confidence (3)

test/testtokenize.cpp:873

• The test currently discards errout_str(). Add an assertion like ASSERT_EQUALS("", errout_str()); to ensure no unexpected errors are emitted during tokenization.

(void)errout_str();

test/testsimplifytypedef.cpp:253

• The original TEST_CASE(typedefInfo2) registration was removed, so its test will no longer run. Either restore TEST_CASE(typedefInfo2) or remove its function definition to keep the suite consistent.

TEST_CASE(typedefInfo3);

lib/tokenize.cpp:1951

• This pattern only matches single-level using X::Y; and misses global-namespace or nested qualifiers (e.g., using ::X::Y;). Consider extending the match to also cover using :: %name% ::|; or refactor using logic to handle all valid cases.

if (cpp && Token::Match(tok2->previous(), "using %name% ::|;")) {

[danmar]

This PR is about making simplifyTypedef less aggressive. It would simplify "using" that was not supposed to be simplified.

[danmar]

I created https://trac.cppcheck.net/ticket/13872 about your issue