make path_statements lint machine applicable for statements with no effect

[yaahc]

The motivation for this change is to make it easier to clean up code generated by c2rust, which tends to include a lot of unnecessary path statements.

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[jieyouxu]

Suggestion: since this is machine-applicable, can you add a test case for the suggestion where the stmt span constitutes of macro_call!();, where macro_call!()-the-expr-span might have a different syntax context?

(Unless this already exists, ofc)

[nnethercote]

@rustbot author

[rustbot]

⚠️ Warning ⚠️

• This PR is based on an upstream commit that is 26 days old.

  It's recommended to update your branch according to the rustc-dev-guide.

[yaahc]

@jieyouxu is this what you meant? Right now this is emitting the lint. Is the idea that this lint shouldn't be emitted the lint in this case or that it shouldn't be machine applicable?

[jieyouxu]

I somehow completely lost this notification, sorry about that. Now that I read my own comment #140830 (review) back, I think what I had in mind at the time was stuff like having a path statement that comes from a macro expansion from another crate, where I think I thought that a machine-applicable suggestion in that case wouldn't be very actionable.

... But that can be a follow-up or further adjusted as suitable, and does not need to block this PR at all.

[rust-log-analyzer]

The job aarch64-gnu-llvm-19-1 failed! Check out the build log: (web) (plain)

Click to see the possible cause of the failure (guessed by this bot)

failures:

---- [ui] tests/ui/lint/warn-path-statement.rs stdout ----

error: /checkout/tests/ui/lint/warn-path-statement.rs:20: unexpected ERROR: '20:13: 20:16: path statement with no effect [path_statements]'

error: 1 unexpected errors found, 0 expected errors not found
status: exit status: 1
command: env -u RUSTC_LOG_COLOR RUSTC_ICE="0" RUST_BACKTRACE="short" "/checkout/obj/build/aarch64-unknown-linux-gnu/stage2/bin/rustc" "/checkout/tests/ui/lint/warn-path-statement.rs" "-Zthreads=1" "-Zsimulate-remapped-rust-src-base=/rustc/FAKE_PREFIX" "-Ztranslate-remapped-path-to-local-path=no" "-Z" "ignore-directory-in-diagnostics-source-blocks=/cargo" "-Z" "ignore-directory-in-diagnostics-source-blocks=/checkout/vendor" "--sysroot" "/checkout/obj/build/aarch64-unknown-linux-gnu/stage2" "--target=aarch64-unknown-linux-gnu" "--check-cfg" "cfg(test,FALSE)" "--error-format" "json" "--json" "future-incompat" "-Ccodegen-units=1" "-Zui-testing" "-Zdeduplicate-diagnostics=no" "-Zwrite-long-types-to-disk=no" "-Cstrip=debuginfo" "--emit" "metadata" "-C" "prefer-dynamic" "--out-dir" "/checkout/obj/build/aarch64-unknown-linux-gnu/test/ui/lint/warn-path-statement" "-A" "unused" "-A" "internal_features" "-Crpath" "-Cdebuginfo=0" "-Lnative=/checkout/obj/build/aarch64-unknown-linux-gnu/native/rust-test-helpers" "-D" "path-statements"

--- unexpected errors (from JSON output) ---
ERRORline  20: 20:13: 20:16: path statement with no effect [path_statements]
---

thread '[ui] tests/ui/lint/warn-path-statement.rs' panicked at src/tools/compiletest/src/runtest.rs:790:13:
errors differ from expected
note: run with `RUST_BACKTRACE=1` environment variable to display a backtrace

[yaahc]

@rustbot ready

[nnethercote]

r? @jieyouxu

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[jieyouxu]

Note: I think you'll need a

//~^ ERROR: path statement with no effect

annotation here. I guess partly what I had in mind re. macros was also this case, where the suggestion is tied to removing $e;, though arguably maybe it's the invocation foo!(x); that should be removed.

Again, this is not blocking IMO.

[jieyouxu]

Sorry about losing the notification, I just had some thoughts on the suggestion which are not blocking. Feel free to r=me after adding the missing error annotation.

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