Rollup merge of #119388 - Enselic:prevent-lint-triplication, r=cjgillot

rustc_lint: Prevent triplication of various lints

Prevent triplication of various lints. The triplication happens because we run the same lint three times (or less in some cases):
* In `BuiltinCombinedPreExpansionLintPass`
* In `BuiltinCombinedEarlyLintPass`
* In `shallow_lint_levels_on()`

Only run the lints one time by checking the `lint_added_lints` bool.

Set your GitHub diff setting to ignore whitespaces changes when reviewing this PR, since I had to enclose a block inside an if.

Closes #73301

(I found this while exploring the code related to [this](#119251 (comment)) comment.)

Author: matthiaskrgr

compiler/rustc_error_codes/src/error_codes/E0453.md

@@ -8,8 +8,8 @@ Example of erroneous code:
 
 #[allow(non_snake_case)]
 fn main() {
-    let MyNumber = 2; // error: allow(non_snake_case) overruled by outer
-                      //        forbid(non_snake_case)
+    // error: allow(non_snake_case) incompatible with previous forbid
+    let MyNumber = 2;
 }
 ```
 

compiler/rustc_lint/src/context.rs

@@ -1069,7 +1069,7 @@ impl<'a> EarlyContext<'a> {
     pub(crate) fn new(
         sess: &'a Session,
         features: &'a Features,
-        warn_about_weird_lints: bool,
+        lint_added_lints: bool,
         lint_store: &'a LintStore,
         registered_tools: &'a RegisteredTools,
         buffered: LintBuffer,
@@ -1078,7 +1078,7 @@ impl<'a> EarlyContext<'a> {
             builder: LintLevelsBuilder::new(
                 sess,
                 features,
-                warn_about_weird_lints,
+                lint_added_lints,
                 lint_store,
                 registered_tools,
             ),

compiler/rustc_lint/src/levels.rs

@@ -135,7 +135,7 @@ fn lint_expectations(tcx: TyCtxt<'_>, (): ()) -> Vec<(LintExpectationId, LintExp
             unstable_to_stable_ids: FxHashMap::default(),
             empty: FxHashMap::default(),
         },
-        warn_about_weird_lints: false,
+        lint_added_lints: false,
         store,
         registered_tools: tcx.registered_tools(()),
     };
@@ -164,7 +164,7 @@ fn shallow_lint_levels_on(tcx: TyCtxt<'_>, owner: hir::OwnerId) -> ShallowLintLe
             empty: FxHashMap::default(),
             attrs,
         },
-        warn_about_weird_lints: false,
+        lint_added_lints: false,
         store,
         registered_tools: tcx.registered_tools(()),
     };
@@ -451,7 +451,7 @@ pub struct LintLevelsBuilder<'s, P> {
     sess: &'s Session,
     features: &'s Features,
     provider: P,
-    warn_about_weird_lints: bool,
+    lint_added_lints: bool,
     store: &'s LintStore,
     registered_tools: &'s RegisteredTools,
 }
@@ -464,15 +464,15 @@ impl<'s> LintLevelsBuilder<'s, TopDown> {
     pub(crate) fn new(
         sess: &'s Session,
         features: &'s Features,
-        warn_about_weird_lints: bool,
+        lint_added_lints: bool,
         store: &'s LintStore,
         registered_tools: &'s RegisteredTools,
     ) -> Self {
         let mut builder = LintLevelsBuilder {
             sess,
             features,
             provider: TopDown { sets: LintLevelSets::new(), cur: COMMAND_LINE },
-            warn_about_weird_lints,
+            lint_added_lints,
             store,
             registered_tools,
         };
@@ -642,7 +642,7 @@ impl<'s, P: LintLevelsProvider> LintLevelsBuilder<'s, P> {
         //
         // This means that this only errors if we're truly lowering the lint
         // level from forbid.
-        if level != Level::Forbid {
+        if self.lint_added_lints && level != Level::Forbid {
             if let Level::Forbid = old_level {
                 // Backwards compatibility check:
                 //
@@ -968,7 +968,7 @@ impl<'s, P: LintLevelsProvider> LintLevelsBuilder<'s, P> {
                         continue;
                     }
 
-                    _ if !self.warn_about_weird_lints => {}
+                    _ if !self.lint_added_lints => {}
 
                     CheckLintNameResult::Renamed(ref replace) => {
                         let suggestion =
@@ -1029,7 +1029,7 @@ impl<'s, P: LintLevelsProvider> LintLevelsBuilder<'s, P> {
             }
         }
 
-        if !is_crate_node {
+        if self.lint_added_lints && !is_crate_node {
             for (id, &(level, ref src)) in self.current_specs().iter() {
                 if !id.lint.crate_level_only {
                     continue;
@@ -1054,33 +1054,33 @@ impl<'s, P: LintLevelsProvider> LintLevelsBuilder<'s, P> {
     /// Checks if the lint is gated on a feature that is not enabled.
     ///
     /// Returns `true` if the lint's feature is enabled.
-    // FIXME only emit this once for each attribute, instead of repeating it 4 times for
-    // pre-expansion lints, post-expansion lints, `shallow_lint_levels_on` and `lint_expectations`.
     #[track_caller]
     fn check_gated_lint(&self, lint_id: LintId, span: Span, lint_from_cli: bool) -> bool {
         if let Some(feature) = lint_id.lint.feature_gate {
             if !self.features.active(feature) {
-                let lint = builtin::UNKNOWN_LINTS;
-                let (level, src) = self.lint_level(builtin::UNKNOWN_LINTS);
-                struct_lint_level(
-                    self.sess,
-                    lint,
-                    level,
-                    src,
-                    Some(span.into()),
-                    fluent::lint_unknown_gated_lint,
-                    |lint| {
-                        lint.set_arg("name", lint_id.lint.name_lower());
-                        lint.note(fluent::lint_note);
-                        rustc_session::parse::add_feature_diagnostics_for_issue(
-                            lint,
-                            &self.sess.parse_sess,
-                            feature,
-                            GateIssue::Language,
-                            lint_from_cli,
-                        );
-                    },
-                );
+                if self.lint_added_lints {
+                    let lint = builtin::UNKNOWN_LINTS;
+                    let (level, src) = self.lint_level(builtin::UNKNOWN_LINTS);
+                    struct_lint_level(
+                        self.sess,
+                        lint,
+                        level,
+                        src,
+                        Some(span.into()),
+                        fluent::lint_unknown_gated_lint,
+                        |lint| {
+                            lint.set_arg("name", lint_id.lint.name_lower());
+                            lint.note(fluent::lint_note);
+                            rustc_session::parse::add_feature_diagnostics_for_issue(
+                                lint,
+                                &self.sess.parse_sess,
+                                feature,
+                                GateIssue::Language,
+                                lint_from_cli,
+                            );
+                        },
+                    );
+                }
                 return false;
             }
         }

tests/ui/error-codes/E0453.rs

@@ -2,6 +2,5 @@
 
 #[allow(non_snake_case)]
 //~^ ERROR allow(non_snake_case) incompatible
-//~| ERROR allow(non_snake_case) incompatible
 fn main() {
 }

tests/ui/error-codes/E0453.stderr

@@ -7,17 +7,6 @@ LL |
 LL | #[allow(non_snake_case)]
    |         ^^^^^^^^^^^^^^ overruled by previous forbid
 
-error[E0453]: allow(non_snake_case) incompatible with previous forbid
-  --> $DIR/E0453.rs:3:9
-   |
-LL | #![forbid(non_snake_case)]
-   |           -------------- `forbid` level set here
-LL |
-LL | #[allow(non_snake_case)]
-   |         ^^^^^^^^^^^^^^ overruled by previous forbid
-   |
-   = note: duplicate diagnostic emitted due to `-Z deduplicate-diagnostics=no`
-
-error: aborting due to 2 previous errors
+error: aborting due to 1 previous error
 
 For more information about this error, try `rustc --explain E0453`.

tests/ui/feature-gates/feature-gate-multiple_supertrait_upcastable.rs

@@ -2,11 +2,7 @@
 
 #![deny(multiple_supertrait_upcastable)]
 //~^ WARNING unknown lint: `multiple_supertrait_upcastable`
-//~| WARNING unknown lint: `multiple_supertrait_upcastable`
-//~| WARNING unknown lint: `multiple_supertrait_upcastable`
 #![warn(multiple_supertrait_upcastable)]
 //~^ WARNING unknown lint: `multiple_supertrait_upcastable`
-//~| WARNING unknown lint: `multiple_supertrait_upcastable`
-//~| WARNING unknown lint: `multiple_supertrait_upcastable`
 
 fn main() {}

tests/ui/feature-gates/feature-gate-multiple_supertrait_upcastable.stderr

@@ -9,53 +9,13 @@ LL | #![deny(multiple_supertrait_upcastable)]
    = note: `#[warn(unknown_lints)]` on by default
 
 warning: unknown lint: `multiple_supertrait_upcastable`
-  --> $DIR/feature-gate-multiple_supertrait_upcastable.rs:7:1
+  --> $DIR/feature-gate-multiple_supertrait_upcastable.rs:5:1
    |
 LL | #![warn(multiple_supertrait_upcastable)]
    | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
    |
    = note: the `multiple_supertrait_upcastable` lint is unstable
    = help: add `#![feature(multiple_supertrait_upcastable)]` to the crate attributes to enable
 
-warning: unknown lint: `multiple_supertrait_upcastable`
-  --> $DIR/feature-gate-multiple_supertrait_upcastable.rs:3:1
-   |
-LL | #![deny(multiple_supertrait_upcastable)]
-   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
-   |
-   = note: the `multiple_supertrait_upcastable` lint is unstable
-   = help: add `#![feature(multiple_supertrait_upcastable)]` to the crate attributes to enable
-   = note: duplicate diagnostic emitted due to `-Z deduplicate-diagnostics=no`
-
-warning: unknown lint: `multiple_supertrait_upcastable`
-  --> $DIR/feature-gate-multiple_supertrait_upcastable.rs:7:1
-   |
-LL | #![warn(multiple_supertrait_upcastable)]
-   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
-   |
-   = note: the `multiple_supertrait_upcastable` lint is unstable
-   = help: add `#![feature(multiple_supertrait_upcastable)]` to the crate attributes to enable
-   = note: duplicate diagnostic emitted due to `-Z deduplicate-diagnostics=no`
-
-warning: unknown lint: `multiple_supertrait_upcastable`
-  --> $DIR/feature-gate-multiple_supertrait_upcastable.rs:3:1
-   |
-LL | #![deny(multiple_supertrait_upcastable)]
-   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
-   |
-   = note: the `multiple_supertrait_upcastable` lint is unstable
-   = help: add `#![feature(multiple_supertrait_upcastable)]` to the crate attributes to enable
-   = note: duplicate diagnostic emitted due to `-Z deduplicate-diagnostics=no`
-
-warning: unknown lint: `multiple_supertrait_upcastable`
-  --> $DIR/feature-gate-multiple_supertrait_upcastable.rs:7:1
-   |
-LL | #![warn(multiple_supertrait_upcastable)]
-   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
-   |
-   = note: the `multiple_supertrait_upcastable` lint is unstable
-   = help: add `#![feature(multiple_supertrait_upcastable)]` to the crate attributes to enable
-   = note: duplicate diagnostic emitted due to `-Z deduplicate-diagnostics=no`
-
-warning: 6 warnings emitted
+warning: 2 warnings emitted
 

tests/ui/feature-gates/feature-gate-non_exhaustive_omitted_patterns_lint.rs

@@ -2,12 +2,8 @@
 
 #![deny(non_exhaustive_omitted_patterns)]
 //~^ WARNING unknown lint: `non_exhaustive_omitted_patterns`
-//~| WARNING unknown lint: `non_exhaustive_omitted_patterns`
-//~| WARNING unknown lint: `non_exhaustive_omitted_patterns`
 #![allow(non_exhaustive_omitted_patterns)]
 //~^ WARNING unknown lint: `non_exhaustive_omitted_patterns`
-//~| WARNING unknown lint: `non_exhaustive_omitted_patterns`
-//~| WARNING unknown lint: `non_exhaustive_omitted_patterns`
 
 fn main() {
     enum Foo {
@@ -19,9 +15,6 @@ fn main() {
     #[allow(non_exhaustive_omitted_patterns)]
     //~^ WARNING unknown lint: `non_exhaustive_omitted_patterns`
     //~| WARNING unknown lint: `non_exhaustive_omitted_patterns`
-    //~| WARNING unknown lint: `non_exhaustive_omitted_patterns`
-    //~| WARNING unknown lint: `non_exhaustive_omitted_patterns`
-    //~| WARNING unknown lint: `non_exhaustive_omitted_patterns`
     match Foo::A {
         //~^ ERROR non-exhaustive patterns: `Foo::C` not covered
         Foo::A => {}
@@ -31,9 +24,6 @@ fn main() {
     #[warn(non_exhaustive_omitted_patterns)]
     //~^ WARNING unknown lint: `non_exhaustive_omitted_patterns`
     //~| WARNING unknown lint: `non_exhaustive_omitted_patterns`
-    //~| WARNING unknown lint: `non_exhaustive_omitted_patterns`
-    //~| WARNING unknown lint: `non_exhaustive_omitted_patterns`
-    //~| WARNING unknown lint: `non_exhaustive_omitted_patterns`
     match Foo::A {
         Foo::A => {}
         Foo::B => {}