[all-commits] [llvm/llvm-project] 217668: [nfc] Allow forwarding `Error` returns from `Expec...

[Mircea Trofin via All-commits]

  Branch: refs/heads/main
  Home:   https://github.com/llvm/llvm-project
  Commit: 217668f641e82f901645f428ae0d07a3c01e9a8a
      https://github.com/llvm/llvm-project/commit/217668f641e82f901645f428ae0d07a3c01e9a8a
  Author: Mircea Trofin <mtrofin at google.com>
  Date:   2024-05-15 (Wed, 15 May 2024)

  Changed paths:
    M llvm/include/llvm/Support/Error.h
    M llvm/lib/Bitstream/Reader/BitstreamReader.cpp
    M llvm/lib/Object/COFFObjectFile.cpp
    M llvm/lib/Object/WindowsResource.cpp

  Log Message:
  -----------
  [nfc] Allow forwarding `Error` returns from `Expected` callers (#92208)

On a few compilers (clang 11/12 for example [1]), the following does not
result in a copy elision, and since `Error`'s copy dtor is elided,
results in a compile error:

```
  Expect<Something> foobar() {
    ...
    if (Error E = aCallReturningError())
      return E;
    ...
  }
```

Moving `E` would, conversely, result in the pessimizing-move warning on
more recent clangs ("moving a local object in a return statement
prevents copy elision")

We just need to make the `Expected` ctor taking an `Error` take it as a
r-value reference.

[1] https://lab.llvm.org/buildbot/#/builders/54/builds/10505



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