[Clang FE] Possible logic issue in `TransformTypos::TransformDesignatedInitExpr`

[d367wang]

When running the tree-visitor TransformTypos on a DesignatedInitExpr node, it first tries to transform its initializer

// transform the initializer value
  ExprResult Init = getDerived().TransformExpr(E->getInit());

and later on decides whether the AST changes by

ExprChanged = ExprChanged || Init.get() != E->getArrayIndex(D);

at

llvm-project/clang/lib/Sema/TreeTransform.h

Line 13659 in 5492199

ExprChanged = ExprChanged || Init.get() != E->getArrayIndex(D);

The logic in Init.get() != E->getArrayIndex(D) seems not correct as the initializer and the index of the designator are being compared, which is likely to always be true. In contrast, later in the same function

llvm-project/clang/lib/Sema/TreeTransform.h

Line 13685 in 5492199

Init.get() == E->getInit() &&

The old initializer and the initializer after transform are compared.

Ran debugger on clang compiling a designator example

const char *str[] = {
    [some_typo] = "0"
};

and stepped in to the line, Init.get() is a StringLiteral and E->getArrayIndex(D) is a TypoExpr.

[llvmbot]

@llvm/issue-subscribers-clang-frontend

Author: None (d367wang)

When running the tree-visitor `TransformTypos` on a `DesignatedInitExpr` node, it first tries to transform its initializer ``` // transform the initializer value ExprResult Init = getDerived().TransformExpr(E->getInit()); ``` and later on decides whether the AST changes by ``` ExprChanged = ExprChanged || Init.get() != E->getArrayIndex(D); ``` at https://github.com/llvm/llvm-project/blob/5492199a9aa4b5d31c38e36928ac153570091d6d/clang/lib/Sema/TreeTransform.h#L13659

The logic in Init.get() != E->getArrayIndex(D) seems not correct as the initializer and the index of the designator are being compared, which is likely to always be false.

Ran debugger on clang compiling a designator example

const char *str[] = {
    [some_typo] = "0"
};

and stepped in to the line, Init.get() is a StringLiteral and E->getArrayIndex(D) is a TypoExpr.

[llvmbot]

Hi!

This issue may be a good introductory issue for people new to working on LLVM. If you would like to work on this issue, your first steps are:

1. Check that no other contributor has already been assigned to this issue. If you believe that no one is actually working on it despite an assignment, ping the person. After one week without a response, the assignee may be changed.
2. In the comments of this issue, request for it to be assigned to you, or just create a pull request after following the steps below. Mention this issue in the description of the pull request.
3. Fix the issue locally.
4. Run the test suite locally. Remember that the subdirectories under test/ create fine-grained testing targets, so you can e.g. use make check-clang-ast to only run Clang's AST tests.
5. Create a Git commit.
6. Run git clang-format HEAD~1 to format your changes.
7. Open a pull request to the upstream repository on GitHub. Detailed instructions can be found in GitHub's documentation. Mention this issue in the description of the pull request.

If you have any further questions about this issue, don't hesitate to ask via a comment in the thread below.

[llvmbot]

@llvm/issue-subscribers-good-first-issue

Author: None (d367wang)

When running the tree-visitor `TransformTypos` on a `DesignatedInitExpr` node, it first tries to transform its initializer ``` // transform the initializer value ExprResult Init = getDerived().TransformExpr(E->getInit()); ``` and later on decides whether the AST changes by ``` ExprChanged = ExprChanged || Init.get() != E->getArrayIndex(D); ``` at https://github.com/llvm/llvm-project/blob/5492199a9aa4b5d31c38e36928ac153570091d6d/clang/lib/Sema/TreeTransform.h#L13659

The logic in Init.get() != E->getArrayIndex(D) seems not correct as the initializer and the index of the designator are being compared, which is likely to always be true. In contrast, later in the same function

llvm-project/clang/lib/Sema/TreeTransform.h

Line 13685 in 5492199

Init.get() == E->getInit() &&

The old initializer and the initializer after transform are compared.

Ran debugger on clang compiling a designator example

const char *str[] = {
    [some_typo] = "0"
};

and stepped in to the line, Init.get() is a StringLiteral and E->getArrayIndex(D) is a TypoExpr.

[beamandala]

Hi, can I work on this issue?