NRVO not eliding copy on immediatly-invoked lambda

[hcmh]

clang trunk from Compiler Explorer does not perform NRVO on the following code (triggering -Wnrvo):

    const char d = 'a';
    const auto b = [] (auto c) {
        std::string a{c};
        return a;
    }(d);

Changing the lambda argument from auto

[] (char c) { ...

or adding an explicit trailing return type:

[] (auto c) -> std::string { ...

does lead to NRVO.

Expected behavior: No error when compiling with -Werror -Wnrvo.
LLVM version: trunk from Compiler Explorer

Example on Compiler Explorer

[llvmbot]

@llvm/issue-subscribers-clang-frontend

Author: Christian Bardey (hcmh)

`clang` trunk from Compiler Explorer does not perform NRVO on the following code (triggering `-Wnrvo`):

    const char d = 'a';
    const auto b = [] (auto c) {
        std::string a{c};
        return a;
    }(d);

Changing the lambda argument from auto

[] (char c) { ...

or adding an explicit trailing return type:

[] (auto c) -> std::string { ...

does lead to NRVO.

Expected behavior: No error when compiling with -Werror -Wnrvo.
LLVM version: trunk from Compiler Explorer

Example on Compiler Explorer

[zwuis]

Maybe related: #38674.

[hcmh]

Maybe related: #38674.

True, that seems like the same or a very similar issue, especially since a fix (add explicit return type) is the same.