[all-commits] [llvm/llvm-project] bc8b19: [Clang] Introduce a trait to determine the structu...

[cor3ntin via All-commits]

  Branch: refs/heads/main
  Home:   https://github.com/llvm/llvm-project
  Commit: bc8b19c7575f3882b7655e129d4fc3b74c7fbba3
      https://github.com/llvm/llvm-project/commit/bc8b19c7575f3882b7655e129d4fc3b74c7fbba3
  Author: cor3ntin <corentinjabot at gmail.com>
  Date:   2025-03-18 (Tue, 18 Mar 2025)

  Changed paths:
    M clang/docs/LanguageExtensions.rst
    M clang/docs/ReleaseNotes.rst
    M clang/include/clang/AST/ExprCXX.h
    M clang/include/clang/AST/Stmt.h
    M clang/include/clang/Basic/DiagnosticSemaKinds.td
    M clang/include/clang/Basic/TokenKinds.def
    M clang/include/clang/Sema/Sema.h
    M clang/lib/AST/ASTImporter.cpp
    M clang/lib/AST/ByteCode/Compiler.cpp
    M clang/lib/AST/ExprCXX.cpp
    M clang/lib/AST/ExprConstant.cpp
    M clang/lib/CodeGen/CGExprScalar.cpp
    M clang/lib/Sema/SemaDeclCXX.cpp
    M clang/lib/Sema/SemaExprCXX.cpp
    M clang/lib/Serialization/ASTReaderStmt.cpp
    M clang/lib/Serialization/ASTWriterStmt.cpp
    M clang/lib/StaticAnalyzer/Core/SValBuilder.cpp
    M clang/test/CodeGenCXX/builtins.cpp
    M clang/test/CodeGenCXX/mangle.cpp
    A clang/test/SemaCXX/builtin-structured-binding-size.cpp

  Log Message:
  -----------
  [Clang] Introduce a trait to determine the structure binding size (#131515)

Introduce a trait to determine the number of bindings that would be
produced by

```cpp

   auto [...p] = expr;

```

This is necessary to implement P2300
(https://eel.is/c++draft/exec#snd.concepts-5), but can also be used to
implement a general get<N> function that supports aggregates

`__builtin_structured_binding_size` is a unary type trait that evaluates
to the number of bindings in a decomposition

If the argument cannot be decomposed, a sfinae-friendly error is
produced.

A type is considered a valid tuple if `std::tuple_size_v<T>` is a valid
expression, even if there is no valid `std::tuple_element`
specialization or suitable `get` function for that type.


Fixes #46049



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