Supress swapping lhs and rhs in equality suggestion in extern macro #144266

xizheyin · 2025-07-21T16:10:32Z

I have tried to find the initial call point via find_oldest_ancestor_in_same_ctxt, but it terminates inside the debug_assert_eq macro and doesn't get the span we were expecting.

For this reason #139316 (comment) , the test can not show the diff.
I test it locally.
In master branch:

error[E0412]: cannot find type `Item` in this scope
 --> src/main.rs:5:5
  |
5 |     Item: Eq + Debug, //~ ERROR cannot find type `Item` in this scope [E0412]
  |     ^^^^ not found in this scope

error[E0308]: mismatched types
 --> src/main.rs:7:35
  |
7 |     debug_assert_eq!(iter.next(), Some(value)); //~ ERROR  mismatched types [E0308]
  |                                   ^^^^^^^^^^^ expected `Option<<I as Iterator>::Item>`, found `Option<&<I as Iterator>::Item>`
  |
  = note: expected enum `Option<_>`
             found enum `Option<&_>`
  = note: `Option<&<I as Iterator>::Item>` implements `PartialEq<Option<<I as Iterator>::Item>>`
help: consider swapping the equality
 --> /home/nju/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/lib/rustlib/src/rust/library/core/src/macros/mod.rs:46:22
  |
46-                 if !(*left_val == *right_val) {
46+                 if !(*right_val == *left_val) {
  |

error[E0308]: mismatched types
 --> src/main.rs:8:29
  |
8 |     assert_eq!(iter.next(), Some(value)); //~ ERROR  mismatched types [E0308]
  |                             ^^^^^^^^^^^ expected `Option<<I as Iterator>::Item>`, found `Option<&<I as Iterator>::Item>`
  |
  = note: expected enum `Option<_>`
             found enum `Option<&_>`
  = note: `Option<&<I as Iterator>::Item>` implements `PartialEq<Option<<I as Iterator>::Item>>`
help: consider swapping the equality
 --> /home/nju/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/lib/rustlib/src/rust/library/core/src/macros/mod.rs:46:22
  |
46-                 if !(*left_val == *right_val) {
46+                 if !(*right_val == *left_val) {
  |

error: aborting due to 3 previous errors

In this branch:

error[E0412]: cannot find type `Item` in this scope
 --> src/main.rs:5:5
  |
5 |     Item: Eq + Debug, //~ ERROR cannot find type `Item` in this scope [E0412]
  |     ^^^^ not found in this scope

error[E0308]: mismatched types
 --> src/main.rs:7:35
  |
7 |     debug_assert_eq!(iter.next(), Some(value)); //~ ERROR  mismatched types [E0308]
  |                                   ^^^^^^^^^^^ expected `Option<<I as Iterator>::Item>`, found `Option<&<I as Iterator>::Item>`
  |
  = note: expected enum `Option<_>`
             found enum `Option<&_>`

error[E0308]: mismatched types
 --> src/main.rs:8:29
  |
8 |     assert_eq!(iter.next(), Some(value)); //~ ERROR  mismatched types [E0308]
  |                             ^^^^^^^^^^^ expected `Option<<I as Iterator>::Item>`, found `Option<&<I as Iterator>::Item>`
  |
  = note: expected enum `Option<_>`
             found enum `Option<&_>`

error: aborting due to 3 previous errors

compiler-errors · 2025-07-21T16:11:25Z

If the test can't actually demonstrate the change, then there's no reason to make this into two commits. Please squash this into one.

compiler/rustc_hir_typeck/src/fn_ctxt/suggestions.rs

xizheyin

Pretty fast review!

@rustbot ready

xizheyin · 2025-07-21T16:16:38Z

compiler/rustc_hir_typeck/src/fn_ctxt/suggestions.rs

+            if rhs_expr.span.in_external_macro(sm) || lhs_expr.span.in_external_macro(sm) {
+                return;
+            }
+


Now I checked both.

compiler/rustc_hir_typeck/src/fn_ctxt/suggestions.rs

xizheyin · 2025-07-23T04:28:25Z

I submitted #144268. We can find the correct span with the newly added methods, thus not needing to suppress this suggestion.

Signed-off-by: xizheyin <[email protected]>

xizheyin

Now, we could reproduce the bug.
@rustbot ready

xizheyin · 2025-08-07T11:54:44Z

compiler/rustc_hir_typeck/src/fn_ctxt/suggestions.rs

+            if let Some(rhs_span) = rhs_expr.span.find_ancestor_not_from_extern_macro(sm)
+                && let Some(lhs_span) = lhs_expr.span.find_ancestor_not_from_extern_macro(sm)


If the == is from the extern macro, it will find the first ancestor that is not from extern macro by find_ancestor_not_from_extern_macro.

xizheyin · 2025-08-07T11:55:53Z

compiler/rustc_hir_typeck/src/fn_ctxt/suggestions.rs

+                } else {
+                    // rhs_span and lhs_span are the same because it from extern macro.
+                    // we should suggest to swap two arguments of the equality
+                    err.span_help(rhs_span, "consider swapping two arguments of the equality");
+                }


Itrhs_span and lhs_span is the same, it is expand from extern macro, we use span_help to hint.

rust-log-analyzer · 2025-08-07T12:33:29Z

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

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

test [ui] tests/ui/zero-sized/zero-sized-btreemap-insert.rs ... ok

failures:

---- [ui] tests/ui/typeck/sugg-swap-equality-in-macro-issue-139050.rs stdout ----
Saved the actual stderr to `/checkout/obj/build/aarch64-unknown-linux-gnu/test/ui/typeck/sugg-swap-equality-in-macro-issue-139050/sugg-swap-equality-in-macro-issue-139050.stderr`
diff of stderr:

26 LL |                 if !(*left_val == *right_val) {
27    |                                   ^^^^^^^^^^ expected `Option<<I as Iterator>::Item>`, found `Option<&<I as Iterator>::Item>`
28 ...
- LL |     eq_local!(assert iter.next(), Some(value)); 
+ LL |     eq_local!(assert iter.next(), Some(value));
30    |     ------------------------------------------ in this macro invocation
31    |
32    = note: expected enum `Option<_>`


The actual stderr differed from the expected stderr
To update references, rerun the tests and pass the `--bless` flag
To only update this specific test, also pass `--test-args typeck/sugg-swap-equality-in-macro-issue-139050.rs`

error: 1 errors occurred comparing output.
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/typeck/sugg-swap-equality-in-macro-issue-139050.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/typeck/sugg-swap-equality-in-macro-issue-139050" "-A" "unused" "-A" "internal_features" "-A" "unused_parens" "-A" "unused_braces" "-Crpath" "-Cdebuginfo=0" "-Lnative=/checkout/obj/build/aarch64-unknown-linux-gnu/native/rust-test-helpers" "-L" "/checkout/obj/build/aarch64-unknown-linux-gnu/test/ui/typeck/sugg-swap-equality-in-macro-issue-139050/auxiliary" "--extern" "ext=/checkout/obj/build/aarch64-unknown-linux-gnu/test/ui/typeck/sugg-swap-equality-in-macro-issue-139050/auxiliary/libextern_macro_issue_139050.so"
stdout: none
--- stderr -------------------------------
error[E0412]: cannot find type `Item` in this scope
##[error]  --> /checkout/tests/ui/typeck/sugg-swap-equality-in-macro-issue-139050.rs:28:5
   |
LL |     Item: Eq + Debug, //~ ERROR cannot find type `Item` in this scope [E0412]
   |     ^^^^ not found in this scope

error[E0308]: mismatched types
##[error]  --> /checkout/tests/ui/typeck/sugg-swap-equality-in-macro-issue-139050.rs:30:5
   |
LL |     ext::eq!(assert iter.next(), Some(value)); //~ ERROR  mismatched types [E0308]
   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ expected `Option<<I as Iterator>::Item>`, found `Option<&<I as Iterator>::Item>`
   |
   = note: expected enum `Option<_>`
              found enum `Option<&_>`
   = note: `Option<&<I as Iterator>::Item>` implements `PartialEq<Option<<I as Iterator>::Item>>`
help: consider swapping two arguments of the equality
  --> /checkout/tests/ui/typeck/sugg-swap-equality-in-macro-issue-139050.rs:30:5
   |
LL |     ext::eq!(assert iter.next(), Some(value)); //~ ERROR  mismatched types [E0308]
   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
   = note: this error originates in the macro `ext::eq` (in Nightly builds, run with -Z macro-backtrace for more info)

error[E0308]: mismatched types
##[error]  --> /checkout/tests/ui/typeck/sugg-swap-equality-in-macro-issue-139050.rs:15:35
   |
LL |                 if !(*left_val == *right_val) { //~ ERROR  mismatched types [E0308]
   |                                   ^^^^^^^^^^ expected `Option<<I as Iterator>::Item>`, found `Option<&<I as Iterator>::Item>`
...
LL |     eq_local!(assert iter.next(), Some(value));
   |     ------------------------------------------ in this macro invocation
   |
   = note: expected enum `Option<_>`
              found enum `Option<&_>`
   = note: `Option<&<I as Iterator>::Item>` implements `PartialEq<Option<<I as Iterator>::Item>>`
   = note: this error originates in the macro `eq_local` (in Nightly builds, run with -Z macro-backtrace for more info)
help: consider swapping the equality
   |
LL -                 if !(*left_val == *right_val) { //~ ERROR  mismatched types [E0308]
LL +                 if !(*right_val == *left_val) { //~ ERROR  mismatched types [E0308]
   |

error: aborting due to 3 previous errors

Some errors have detailed explanations: E0308, E0412.

rustbot assigned compiler-errors Jul 21, 2025

rustbot added S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. T-compiler Relevant to the compiler team, which will review and decide on the PR/issue. labels Jul 21, 2025

xizheyin changed the title ~~139050~~ Supress swapping lhs and rhs in equality suggestion in extern macro Jul 21, 2025

compiler-errors requested changes Jul 21, 2025

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rustbot added S-waiting-on-author Status: This is awaiting some action (such as code changes or more information) from the author. and removed S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. labels Jul 21, 2025

xizheyin force-pushed the 139050 branch 2 times, most recently from 2ec2014 to 749762a Compare July 21, 2025 16:16

xizheyin commented Jul 21, 2025

View reviewed changes

rustbot added S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. and removed S-waiting-on-author Status: This is awaiting some action (such as code changes or more information) from the author. labels Jul 21, 2025

compiler-errors reviewed Jul 21, 2025

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This was referenced Jul 28, 2025

Add method find_ancestor_not_from_macro and find_ancestor_not_from_extern_macro to supersede find_oldest_ancestor_in_same_ctxt #144268

Merged

Suggest only Span without source changes when source code is unavailable #144585

Open

Add test sugg-swap-equality-in-macro

b0812d9

Signed-off-by: xizheyin <[email protected]>

xizheyin force-pushed the 139050 branch from 749762a to 3abc2ff Compare August 7, 2025 11:47

Suggest swapping the equality in user-written code

68ea691

Signed-off-by: xizheyin <[email protected]>

xizheyin force-pushed the 139050 branch from 3abc2ff to 68ea691 Compare August 7, 2025 11:52

xizheyin commented Aug 7, 2025

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Supress swapping lhs and rhs in equality suggestion in extern macro #144266

Supress swapping lhs and rhs in equality suggestion in extern macro #144266

xizheyin commented Jul 21, 2025 •

edited

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rust-log-analyzer commented Aug 7, 2025

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Uh oh!

		if let Some(rhs_span) = rhs_expr.span.find_ancestor_not_from_extern_macro(sm)
		&& let Some(lhs_span) = lhs_expr.span.find_ancestor_not_from_extern_macro(sm)

Supress swapping lhs and rhs in equality suggestion in extern macro #144266

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Supress swapping lhs and rhs in equality suggestion in extern macro #144266

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