[PATCH] D138914: Make evaluation of nested requirement consistent with requires expr.

[Utkarsh Saxena via Phabricator via cfe-commits]

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Fixes: https://github.com/llvm/llvm-project/issues/45563

  template<class T>  concept True = true;
  
  template <class T>
  concept C1 = requires (T) {
     requires True<typename T::value> || True<T>;
  };
  
  template <class T>
  constexpr bool foo()
  requires True<typename T::value> || True<T> {
      return true;
  }
  static_assert(C1<double>); // Previously failed due to SFINAE error
  static_assert(foo<int>()); // but this works fine.

The issue here is the discrepancy between how a nested requirement is evaluated <https://github.com/llvm/llvm-project/blob/main/clang/lib/Sema/SemaTemplateInstantiate.cpp#L2331> Vs how a non-nested requirement is evaluated <https://github.com/llvm/llvm-project/blob/main/clang/lib/Sema/SemaConcept.cpp#L167-L200>.

This patch makes constraint checking consistent for nested requirement
and trailing requires expressions by reusing the same evaluator.


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D138914

Files:
  clang/include/clang/AST/ExprConcepts.h
  clang/lib/Sema/SemaConcept.cpp
  clang/lib/Sema/SemaTemplateInstantiate.cpp
  clang/test/CXX/expr/expr.prim/expr.prim.req/nested-requirement.cpp
  clang/test/SemaTemplate/instantiate-requires-expr.cpp

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