New lint: deref_method_call_chain

[tanndlin]

fixes #2094

• Followed [lint naming conventions][lint_naming]
• Added passing UI tests (including committed .stderr file)
• cargo test passes locally
• Executed cargo dev update_lints
• Added lint documentation
• Run cargo dev fmt

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changelog: New lint [deref_method_call_chain]

[Copilot]

Pull request overview

Adds a new Clippy methods lint, deref_method_call_chain, to detect and suggest removing redundant deref-like conversion calls (e.g., as_slice, as_str, as_path) before method calls when deref coercion would resolve the same inherent method.

Changes:

• Introduces the deref_method_call_chain lint (declaration, registration, implementation) plus a dedicated UI test (with .fixed and .stderr).
• Updates several existing UI tests to allow(clippy::deref_method_call_chain) and refreshes expected .stderr line numbers.
• Minor cleanup in lintcheck to remove a redundant .as_os_str() in a method chain.

Reviewed changes

Copilot reviewed 25 out of 25 changed files in this pull request and generated 1 comment.

Show a summary per file

File	Description
tests/ui/return_and_then.stderr	Updated expected diagnostics line numbers after adding a crate-level allow.
tests/ui/return_and_then.rs	Adds #![allow(clippy::deref_method_call_chain)] to avoid new lint affecting this test.
tests/ui/return_and_then.fixed	Mirrors the new crate-level allow in the rustfix output.
tests/ui/redundant_as_str.stderr	Updated expected diagnostics line numbers after adding a crate-level allow.
tests/ui/redundant_as_str.rs	Adds #![allow(clippy::deref_method_call_chain)] to avoid interaction with new lint.
tests/ui/redundant_as_str.fixed	Mirrors the new crate-level allow in the rustfix output.
tests/ui/new_without_default.stderr	Updated expected diagnostics line numbers after adding a crate-level allow.
tests/ui/new_without_default.rs	Adds #![allow(clippy::deref_method_call_chain)].
tests/ui/new_without_default.fixed	Mirrors the new crate-level allow in the rustfix output.
tests/ui/needless_for_each_fixable.stderr	Updated expected diagnostics line numbers after adding a crate-level allow.
tests/ui/needless_for_each_fixable.rs	Adds #![allow(clippy::deref_method_call_chain)].
tests/ui/needless_for_each_fixable.fixed	Mirrors the new crate-level allow in the rustfix output.
tests/ui/manual_find_fixable.rs	Adds clippy::deref_method_call_chain to existing allow list.
tests/ui/manual_find_fixable.fixed	Mirrors the updated allow list in the rustfix output.
tests/ui/into_iter_without_iter.stderr	Updated expected diagnostics line numbers after adding a crate-level allow.
tests/ui/into_iter_without_iter.rs	Adds #![allow(clippy::deref_method_call_chain)].
tests/ui/deref_method_call_chain.stderr	New UI stderr expectations for the new lint.
tests/ui/deref_method_call_chain.rs	New UI test cases covering std and user-defined deref-like conversions and exclusions.
tests/ui/deref_method_call_chain.fixed	New rustfix output expectations for the new lint.
lintcheck/src/main.rs	Removes a redundant as_os_str() call in a method chain.
clippy_utils/src/sym.rs	Adds extra symbols used by the new lint implementation/tests.
clippy_lints/src/methods/mod.rs	Declares, registers, and calls the new lint from the Methods pass.
clippy_lints/src/methods/deref_method_call_chain.rs	Implements the new lint logic and suggestion.
clippy_lints/src/declared_lints.rs	Adds the lint to the declared lint registry.
CHANGELOG.md	Adds a documentation link entry for the new lint.

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View changes since this review

[tanndlin]

Fixed and added test cases, but did not take suggested code

[github-actions]

Lintcheck changes for ee6b42f

Lint	Added	Removed	Changed
clippy::deref_method_call_chain	14	0	0

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