[all-commits] [llvm/llvm-project] c9aaf3: [SemaCXX] Handle lack of TypeSourceInfo on special...

[Bruno Cardoso Lopes via All-commits]

  Branch: refs/heads/main
  Home:   https://github.com/llvm/llvm-project
  Commit: c9aaf34b8db884faa3d3ced4d2fb88fd45697408
      https://github.com/llvm/llvm-project/commit/c9aaf34b8db884faa3d3ced4d2fb88fd45697408
  Author: Bruno Cardoso Lopes <bruno.cardoso at gmail.com>
  Date:   2021-06-22 (Tue, 22 Jun 2021)

  Changed paths:
    M clang/lib/Sema/SemaDeclCXX.cpp
    M clang/lib/Sema/SemaTemplateInstantiate.cpp
    M clang/lib/Sema/SemaTemplateInstantiateDecl.cpp
    M clang/lib/Sema/TreeTransform.h
    A clang/test/SemaCXX/lambdas-implicit-explicit-template.cpp

  Log Message:
  -----------
  [SemaCXX] Handle lack of TypeSourceInfo on special member functions in templated lambdas

During template instantiation involving templated lambdas, clang
could hit an assertion in `TemplateDeclInstantiator::SubstFunctionType`
since the functions are not associated with any `TypeSourceInfo`:

`assert(OldTInfo && "substituting function without type source info");`

This path is triggered when using templated lambdas like the one added as
a test to this patch. To fix this:

- Create `TypeSourceInfo`s for special members and make sure the template
instantiator can get through all patterns.
- Introduce a `SpecialMemberTypeInfoRebuilder` tree transform to rewrite
such member function arguments. Without this, we get errors like:

`error: only special member functions and comparison operators may be defaulted`

since `getDefaultedFunctionKind` can't properly recognize these functions
as special members as part of `SetDeclDefaulted`.

Fixes PR45828 and PR44848

Differential Revision: https://reviews.llvm.org/D88327