[PATCH] D123668: [Testing] TestAST, a helper for writing straight-line AST tests

[Sam McCall via Phabricator via cfe-commits]

sammccall created this revision.
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Tests that need ASTs have to deal with the awkward control flow of
FrontendAction in some way. There are a few idioms used:

- don't bother with unit tests, use clang -dump-ast
- create an ASTConsumer by hand, which is bulky
- use ASTMatchFinder - works pretty well if matchers are actually needed, very strange if they are not
- use ASTUnit - this yields nice straight-line code, but ASTUnit is a terrifically complicated library not designed for this purpose

TestAST provides a very simple way to write straight-line tests: specify
the code/flags and it provides an AST that is kept alive until the
object is destroyed.
It's loosely modeled after TestTU in clangd, which we've successfully
used for a variety of tests.

I've updated a couple of clang tests to use this helper, IMO they're clearer.


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D123668

Files:
  clang/include/clang/Basic/Diagnostic.h
  clang/include/clang/Testing/CommandLineArgs.h
  clang/include/clang/Testing/TestAST.h
  clang/lib/Basic/Diagnostic.cpp
  clang/lib/Testing/CMakeLists.txt
  clang/lib/Testing/CommandLineArgs.cpp
  clang/lib/Testing/TestAST.cpp
  clang/unittests/Tooling/CMakeLists.txt
  clang/unittests/Tooling/FixItTest.cpp
  clang/unittests/Tooling/StandardLibraryTest.cpp

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