[PATCH] D134618: [Syntax] Fix macro-arg handling in TokenBuffer::spelledForExpanded

[Sam McCall via Phabricator via cfe-commits]

sammccall created this revision.
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A few cases were not handled correctly. Notably:

  #define ID(X) X
  #define HIDE a ID(b)
  HIDE

spelledForExpanded() would claim HIDE is an equivalent range of the 'b' it
contains, despite the fact that HIDE also covers 'a'.

While trying to fix this bug, I found findCommonRangeForMacroArgs hard
to understand (both the implementation and how it's used in spelledForExpanded).
It relies on details of the SourceLocation graph that are IMO fairly obscure.
So I've added/revised quite a lot of comments and made some naming tweaks.

Fixes https://github.com/clangd/clangd/issues/1289


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D134618

Files:
  clang/lib/Tooling/Syntax/Tokens.cpp
  clang/unittests/Tooling/Syntax/TokensTest.cpp

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