Do not point at #[allow(_)] as the reason for compat lint triggering

Fix #121009.

compiler/rustc_middle/src/lint.rs

@@ -207,6 +207,11 @@ pub fn explain_lint_level_source(
     err: &mut Diagnostic,
 ) {
     let name = lint.name_lower();
+    if let Level::Allow = level {
+        // Do not point at `#[allow(compat_lint)]` as the reason for a compatibility lint
+        // triggering. (#121009)
+        return;
+    }
     match src {
         LintLevelSource::Default => {
             err.note_once(format!("`#[{}({})]` on by default", level.as_str(), name));

tests/ui/consts/issue-89088.stderr

@@ -9,9 +9,4 @@ LL |         FOO => todo!(),
    = note: for more information, see issue #120362 <https://github.com/rust-lang/rust/issues/120362>
    = note: the traits must be derived, manual `impl`s are not sufficient
    = note: see https://doc.rust-lang.org/stable/std/marker/trait.StructuralPartialEq.html for details
-note: the lint level is defined here
-  --> $DIR/issue-89088.rs:5:10
-   |
-LL | #![allow(indirect_structural_match)]
-   |          ^^^^^^^^^^^^^^^^^^^^^^^^^
 

tests/ui/lint/future-incompat-json-test.stderr

@@ -1,10 +1,7 @@
-{"$message_type":"future_incompat","future_incompat_report":[{"diagnostic":{"$message_type":"diagnostic","message":"unused variable: `x`","code":{"code":"unused_variables","explanation":null},"level":"warning","spans":[{"file_name":"$DIR/future-incompat-json-test.rs","byte_start":338,"byte_end":339,"line_start":9,"line_end":9,"column_start":9,"column_end":10,"is_primary":true,"text":[{"text":"    let x = 1;","highlight_start":9,"highlight_end":10}],"label":null,"suggested_replacement":null,"suggestion_applicability":null,"expansion":null}],"children":[{"message":"`-A unused-variables` implied by `-A unused`","code":null,"level":"note","spans":[],"children":[],"rendered":null},{"message":"to override `-A unused` add `#[allow(unused_variables)]`","code":null,"level":"help","spans":[],"children":[],"rendered":null},{"message":"if this is intentional, prefix it with an underscore","code":null,"level":"help","spans":[{"file_name":"$DIR/future-incompat-json-test.rs","byte_start":338,"byte_end":339,"line_start":9,"line_end":9,"column_start":9,"column_end":10,"is_primary":true,"text":[{"text":"    let x = 1;","highlight_start":9,"highlight_end":10}],"label":null,"suggested_replacement":"_x","suggestion_applicability":"MaybeIncorrect","expansion":null}],"children":[],"rendered":null}],"rendered":"warning: unused variable: `x`
+{"$message_type":"future_incompat","future_incompat_report":[{"diagnostic":{"$message_type":"diagnostic","message":"unused variable: `x`","code":{"code":"unused_variables","explanation":null},"level":"warning","spans":[{"file_name":"$DIR/future-incompat-json-test.rs","byte_start":338,"byte_end":339,"line_start":9,"line_end":9,"column_start":9,"column_end":10,"is_primary":true,"text":[{"text":"    let x = 1;","highlight_start":9,"highlight_end":10}],"label":null,"suggested_replacement":null,"suggestion_applicability":null,"expansion":null}],"children":[{"message":"if this is intentional, prefix it with an underscore","code":null,"level":"help","spans":[{"file_name":"$DIR/future-incompat-json-test.rs","byte_start":338,"byte_end":339,"line_start":9,"line_end":9,"column_start":9,"column_end":10,"is_primary":true,"text":[{"text":"    let x = 1;","highlight_start":9,"highlight_end":10}],"label":null,"suggested_replacement":"_x","suggestion_applicability":"MaybeIncorrect","expansion":null}],"children":[],"rendered":null}],"rendered":"warning: unused variable: `x`
   --> $DIR/future-incompat-json-test.rs:9:9
    |
 LL |     let x = 1;
    |         ^ help: if this is intentional, prefix it with an underscore: `_x`
-   |
-   = note: `-A unused-variables` implied by `-A unused`
-   = help: to override `-A unused` add `#[allow(unused_variables)]`
 
 "}}]}

tests/ui/lint/future-incompat-test.stderr

@@ -4,7 +4,4 @@ warning: unused variable: `x`
    |
 LL |     let x = 1;
    |         ^ help: if this is intentional, prefix it with an underscore: `_x`
-   |
-   = note: `-A unused-variables` implied by `-A unused`
-   = help: to override `-A unused` add `#[allow(unused_variables)]`
 

tests/ui/lint/semicolon-in-expressions-from-macros/semicolon-in-expressions-from-macros.stderr

@@ -60,11 +60,6 @@ LL |         foo!(first)
    = note: for more information, see issue #79813 <https://github.com/rust-lang/rust/issues/79813>
    = note: macro invocations at the end of a block are treated as expressions
    = note: to ignore the value produced by the macro, add a semicolon after the invocation of `foo`
-note: the lint level is defined here
-  --> $DIR/semicolon-in-expressions-from-macros.rs:24:13
-   |
-LL |     #[allow(semicolon_in_expressions_from_macros)]
-   |             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
    = note: this warning originates in the macro `foo` (in Nightly builds, run with -Z macro-backtrace for more info)
 
 Future breakage diagnostic:
@@ -79,11 +74,6 @@ LL |     let _ = foo!(second);
    |
    = warning: this was previously accepted by the compiler but is being phased out; it will become a hard error in a future release!
    = note: for more information, see issue #79813 <https://github.com/rust-lang/rust/issues/79813>
-note: the lint level is defined here
-  --> $DIR/semicolon-in-expressions-from-macros.rs:29:13
-   |
-LL |     #[allow(semicolon_in_expressions_from_macros)]
-   |             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
    = note: this warning originates in the macro `foo` (in Nightly builds, run with -Z macro-backtrace for more info)
 
 Future breakage diagnostic:
@@ -98,11 +88,6 @@ LL |         let _ = foo!(third);
    |
    = warning: this was previously accepted by the compiler but is being phased out; it will become a hard error in a future release!
    = note: for more information, see issue #79813 <https://github.com/rust-lang/rust/issues/79813>
-note: the lint level is defined here
-  --> $DIR/semicolon-in-expressions-from-macros.rs:32:13
-   |
-LL |     #[allow(semicolon_in_expressions_from_macros)]
-   |             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
    = note: this warning originates in the macro `foo` (in Nightly builds, run with -Z macro-backtrace for more info)
 
 Future breakage diagnostic:
@@ -117,11 +102,6 @@ LL |         let _ = foo!(fourth);
    |
    = warning: this was previously accepted by the compiler but is being phased out; it will become a hard error in a future release!
    = note: for more information, see issue #79813 <https://github.com/rust-lang/rust/issues/79813>
-note: the lint level is defined here
-  --> $DIR/semicolon-in-expressions-from-macros.rs:37:13
-   |
-LL |     #[allow(semicolon_in_expressions_from_macros)]
-   |             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
    = note: this warning originates in the macro `foo` (in Nightly builds, run with -Z macro-backtrace for more info)
 
 Future breakage diagnostic:

tests/ui/pattern/usefulness/const-partial_eq-fallback-ice.stderr

@@ -20,10 +20,4 @@ LL |     if let CONSTANT = &&MyType {
    = note: for more information, see issue #120362 <https://github.com/rust-lang/rust/issues/120362>
    = note: the traits must be derived, manual `impl`s are not sufficient
    = note: see https://doc.rust-lang.org/stable/std/marker/trait.StructuralPartialEq.html for details
-note: the lint level is defined here
-  --> $DIR/const-partial_eq-fallback-ice.rs:1:10
-   |
-LL | #![allow(warnings)]
-   |          ^^^^^^^^
-   = note: `#[allow(indirect_structural_match)]` implied by `#[allow(warnings)]`
 

tests/ui/proc-macro/generate-mod.stderr

@@ -139,11 +139,6 @@ LL | #[derive(generate_mod::CheckDeriveLint)] // OK, lint is suppressed
    |
    = warning: this was previously accepted by the compiler but is being phased out; it will become a hard error in a future release!
    = note: for more information, see issue #83583 <https://github.com/rust-lang/rust/issues/83583>
-note: the lint level is defined here
-  --> $DIR/generate-mod.rs:30:10
-   |
-LL | #[derive(generate_mod::CheckDeriveLint)] // OK, lint is suppressed
-   |          ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
    = note: this warning originates in the derive macro `generate_mod::CheckDeriveLint` (in Nightly builds, run with -Z macro-backtrace for more info)
 
 Future breakage diagnostic:
@@ -155,10 +150,5 @@ LL | #[derive(generate_mod::CheckDeriveLint)] // OK, lint is suppressed
    |
    = warning: this was previously accepted by the compiler but is being phased out; it will become a hard error in a future release!
    = note: for more information, see issue #83583 <https://github.com/rust-lang/rust/issues/83583>
-note: the lint level is defined here
-  --> $DIR/generate-mod.rs:30:10
-   |
-LL | #[derive(generate_mod::CheckDeriveLint)] // OK, lint is suppressed
-   |          ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
    = note: this warning originates in the derive macro `generate_mod::CheckDeriveLint` (in Nightly builds, run with -Z macro-backtrace for more info)
 

tests/ui/traits/issue-33140-hack-boundaries.stderr

@@ -77,9 +77,4 @@ LL | impl Trait0 for dyn Send {}
    |
    = warning: this was previously accepted by the compiler but is being phased out; it will become a hard error in a future release!
    = note: for more information, see issue #56484 <https://github.com/rust-lang/rust/issues/56484>
-note: the lint level is defined here
-  --> $DIR/issue-33140-hack-boundaries.rs:2:10
-   |
-LL | #![allow(order_dependent_trait_objects)]
-   |          ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^