[PATCH] D103087: [clang-tidy] performances-unnecessary-* checks: Extend isOnlyUsedAsConst to expressions and catch const methods returning non-const references/pointers.

[Felix Berger via Phabricator via cfe-commits]

flx created this revision.
flx added reviewers: aaron.ballman, hokein, ymandel.
Herald added a subscriber: xazax.hun.
flx requested review of this revision.
Herald added a project: clang-tools-extra.
Herald added a subscriber: cfe-commits.

This change extends isOnlyUsedAsConst() to avoid false positives in cases where
a const method returns a mutable pointer or refernce and the pointed to object
is modified.

To achieve this we look at each const method or operator call and check if it
returns a mutable pointer/reference. If that's the case the call expression
itself is checked for constant use.

We also capture assignments of expressions to non-const references/pointers and
then check that the declared alias variables are used in a const-only fasion as
well.


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D103087

Files:
  clang-tools-extra/clang-tidy/utils/DeclRefExprUtils.cpp
  clang-tools-extra/clang-tidy/utils/DeclRefExprUtils.h
  clang-tools-extra/clang-tidy/utils/Matchers.h
  clang-tools-extra/test/clang-tidy/checkers/performance-unnecessary-copy-initialization.cpp

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