Make MissingDebugImplementation a module lint.

Author: cjgillot

compiler/rustc_lint/src/builtin.rs

@@ -39,7 +39,7 @@ use crate::{
         BuiltinUnstableFeatures, BuiltinUnusedDocComment, BuiltinUnusedDocCommentSub,
         BuiltinWhileTrue, SuggestChangingAssocTypes,
     },
-    EarlyContext, EarlyLintPass, LateContext, LateLintPass, LintContext,
+    EarlyContext, EarlyLintPass, LateContext, LateLintPass, Level, LintContext,
 };
 use hir::IsAsync;
 use rustc_ast::attr;
@@ -51,7 +51,7 @@ use rustc_errors::{Applicability, DecorateLint, MultiSpan};
 use rustc_feature::{deprecated_attributes, AttributeGate, BuiltinAttribute, GateIssue, Stability};
 use rustc_hir as hir;
 use rustc_hir::def::{DefKind, Res};
-use rustc_hir::def_id::{DefId, LocalDefId, LocalDefIdSet, CRATE_DEF_ID};
+use rustc_hir::def_id::{DefId, LocalDefId, CRATE_DEF_ID};
 use rustc_hir::intravisit::FnKind as HirFnKind;
 use rustc_hir::{Body, FnDecl, GenericParamKind, Node, PatKind, PredicateOrigin};
 use rustc_middle::lint::in_external_macro;
@@ -774,9 +774,7 @@ declare_lint! {
 }
 
 #[derive(Default)]
-pub struct MissingDebugImplementations {
-    impling_types: Option<LocalDefIdSet>,
-}
+pub(crate) struct MissingDebugImplementations;
 
 impl_lint_pass!(MissingDebugImplementations => [MISSING_DEBUG_IMPLEMENTATIONS]);
 
@@ -793,21 +791,18 @@ impl<'tcx> LateLintPass<'tcx> for MissingDebugImplementations {
 
         let Some(debug) = cx.tcx.get_diagnostic_item(sym::Debug) else { return };
 
-        if self.impling_types.is_none() {
-            let mut impls = LocalDefIdSet::default();
-            cx.tcx.for_each_impl(debug, |d| {
-                if let Some(ty_def) = cx.tcx.type_of(d).instantiate_identity().ty_adt_def() {
-                    if let Some(def_id) = ty_def.did().as_local() {
-                        impls.insert(def_id);
-                    }
-                }
-            });
-
-            self.impling_types = Some(impls);
-            debug!("{:?}", self.impling_types);
+        // Avoid listing trait impls if the trait is allowed.
+        let (level, _) = cx.tcx.lint_level_at_node(MISSING_DEBUG_IMPLEMENTATIONS, item.hir_id());
+        if level == Level::Allow {
+            return;
         }
 
-        if !self.impling_types.as_ref().unwrap().contains(&item.owner_id.def_id) {
+        let has_impl = cx
+            .tcx
+            .non_blanket_impls_for_ty(debug, cx.tcx.type_of(item.owner_id).instantiate_identity())
+            .next()
+            .is_some();
+        if !has_impl {
             cx.emit_spanned_lint(
                 MISSING_DEBUG_IMPLEMENTATIONS,
                 item.span,

compiler/rustc_lint/src/lib.rs

@@ -193,10 +193,6 @@ late_lint_methods!(
         [
             // Tracks attributes of parents
             MissingDoc: MissingDoc::new(),
-            // Builds a global list of all impls of `Debug`.
-            // FIXME: Turn the computation of types which implement Debug into a query
-            // and change this to a module lint pass
-            MissingDebugImplementations: MissingDebugImplementations::default(),
         ]
     ]
 );
@@ -253,6 +249,7 @@ late_lint_methods!(
             OpaqueHiddenInferredBound: OpaqueHiddenInferredBound,
             MultipleSupertraitUpcastable: MultipleSupertraitUpcastable,
             MapUnitFn: MapUnitFn,
+            MissingDebugImplementations: MissingDebugImplementations,
         ]
     ]
 );

tests/ui/lint/issue-111359.stderr

@@ -1,26 +1,26 @@
-error: type does not implement `Debug`; consider adding `#[derive(Debug)]` or a manual implementation
+error: type could implement `Copy`; consider adding `impl Copy`
   --> $DIR/issue-111359.rs:7:5
    |
 LL |     pub struct BarPub;
    |     ^^^^^^^^^^^^^^^^^^
    |
 note: the lint level is defined here
-  --> $DIR/issue-111359.rs:1:8
+  --> $DIR/issue-111359.rs:2:8
    |
-LL | #[deny(missing_debug_implementations)]
-   |        ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+LL | #[deny(missing_copy_implementations)]
+   |        ^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
-error: type could implement `Copy`; consider adding `impl Copy`
+error: type does not implement `Debug`; consider adding `#[derive(Debug)]` or a manual implementation
   --> $DIR/issue-111359.rs:7:5
    |
 LL |     pub struct BarPub;
    |     ^^^^^^^^^^^^^^^^^^
    |
 note: the lint level is defined here
-  --> $DIR/issue-111359.rs:2:8
+  --> $DIR/issue-111359.rs:1:8
    |
-LL | #[deny(missing_copy_implementations)]
-   |        ^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+LL | #[deny(missing_debug_implementations)]
+   |        ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
 error: aborting due to 2 previous errors
 

tests/ui/missing_debug_impls.rs

@@ -35,4 +35,4 @@ struct PrivateStruct;
 enum PrivateEnum {}
 
 #[derive(Debug)]
-struct GenericType<T>(T);
+pub struct GenericType<T>(T);