Migrate trait_impl_difference.rs

Author: IntQuant

compiler/rustc_error_messages/locales/en-US/infer.ftl

@@ -211,3 +211,13 @@ infer_trait_placeholder_mismatch = implementation of `{$trait_def_id}` is not ge
     .label_satisfy = doesn't satisfy where-clause
     .label_where = due to a where-clause on `{$def_id}`...
     .label_dup = implementation of `{$trait_def_id}` is not general enough
+
+infer_trait_impl_diff = `impl` item signature doesn't match `trait` item signature
+    .found = found `{$found}`
+    .expected = expected `{$expected}`
+    .expected_found = expected `{$expected}`
+               {"   "}found `{$found}`
+
+infer_tid_rel_help = verify the lifetime relationships in the `trait` and `impl` between the `self` argument, the other inputs and its output
+infer_tid_consider_borriwing = consider borrowing this type parameter in the trait
+infer_tid_param_help = the lifetime requirements from the `impl` do not correspond to the requirements in the `trait`

compiler/rustc_infer/src/errors/mod.rs

@@ -581,3 +581,41 @@ pub struct TraitPlaceholderMismatch {
     #[subdiagnostic]
     pub actual_impl_expl_notes: Vec<ActualImplExplNotes>,
 }
+
+pub struct ConsiderBorrowingParamHelp {
+    pub spans: Vec<Span>,
+}
+
+impl AddSubdiagnostic for ConsiderBorrowingParamHelp {
+    fn add_to_diagnostic(self, diag: &mut rustc_errors::Diagnostic) {
+        let mut type_param_span: MultiSpan = self.spans.clone().into();
+        for &span in &self.spans {
+            type_param_span.push_span_label(span, fluent::infer::tid_consider_borriwing);
+        }
+        diag.span_help(type_param_span, fluent::infer::tid_param_help);
+    }
+}
+
+#[derive(SessionSubdiagnostic)]
+#[help(infer::tid_rel_help)]
+pub struct RelationshipHelp;
+
+#[derive(SessionDiagnostic)]
+#[diag(infer::trait_impl_diff)]
+pub struct TraitImplDiff {
+    #[primary_span]
+    #[label(infer::found)]
+    pub sp: Span,
+    #[label(infer::expected)]
+    pub trait_sp: Span,
+    #[note(infer::expected_found)]
+    pub note: (),
+    #[subdiagnostic]
+    pub param_help: ConsiderBorrowingParamHelp,
+    #[subdiagnostic]
+    // Seems like subdiagnostics are always pushed to the end, so this one
+    // also has to be a subdiagnostic to maintain order.
+    pub rel_help: Option<RelationshipHelp>,
+    pub expected: String,
+    pub found: String,
+}

compiler/rustc_infer/src/infer/error_reporting/nice_region_error/trait_impl_difference.rs

@@ -1,10 +1,11 @@
 //! Error Reporting for `impl` items that do not match the obligations from their `trait`.
 
+use crate::errors::{ConsiderBorrowingParamHelp, RelationshipHelp, TraitImplDiff};
 use crate::infer::error_reporting::nice_region_error::NiceRegionError;
 use crate::infer::lexical_region_resolve::RegionResolutionError;
 use crate::infer::Subtype;
 use crate::traits::ObligationCauseCode::CompareImplItemObligation;
-use rustc_errors::{ErrorGuaranteed, MultiSpan};
+use rustc_errors::ErrorGuaranteed;
 use rustc_hir as hir;
 use rustc_hir::def::Res;
 use rustc_hir::def_id::DefId;
@@ -51,10 +52,6 @@ impl<'a, 'tcx> NiceRegionError<'a, 'tcx> {
         trait_def_id: DefId,
     ) -> ErrorGuaranteed {
         let trait_sp = self.tcx().def_span(trait_def_id);
-        let mut err = self
-            .tcx()
-            .sess
-            .struct_span_err(sp, "`impl` item signature doesn't match `trait` item signature");
 
         // Mark all unnamed regions in the type with a number.
         // This diagnostic is called in response to lifetime errors, so be informative.
@@ -91,9 +88,6 @@ impl<'a, 'tcx> NiceRegionError<'a, 'tcx> {
         let found =
             self.cx.extract_inference_diagnostics_data(found.into(), Some(found_highlight)).name;
 
-        err.span_label(sp, &format!("found `{}`", found));
-        err.span_label(trait_sp, &format!("expected `{}`", expected));
-
         // Get the span of all the used type parameters in the method.
         let assoc_item = self.tcx().associated_item(trait_def_id);
         let mut visitor = TypeParamSpanVisitor { tcx: self.tcx(), types: vec![] };
@@ -110,26 +104,18 @@ impl<'a, 'tcx> NiceRegionError<'a, 'tcx> {
             }
             _ => {}
         }
-        let mut type_param_span: MultiSpan = visitor.types.to_vec().into();
-        for &span in &visitor.types {
-            type_param_span
-                .push_span_label(span, "consider borrowing this type parameter in the trait");
-        }
 
-        err.note(&format!("expected `{}`\n   found `{}`", expected, found));
-
-        err.span_help(
-            type_param_span,
-            "the lifetime requirements from the `impl` do not correspond to the requirements in \
-             the `trait`",
-        );
-        if visitor.types.is_empty() {
-            err.help(
-                "verify the lifetime relationships in the `trait` and `impl` between the `self` \
-                 argument, the other inputs and its output",
-            );
-        }
-        err.emit()
+        let diag = TraitImplDiff {
+            sp,
+            trait_sp,
+            note: (),
+            param_help: ConsiderBorrowingParamHelp { spans: visitor.types.to_vec() },
+            rel_help: visitor.types.is_empty().then_some(RelationshipHelp),
+            expected,
+            found,
+        };
+
+        self.tcx().sess.emit_err(diag)
     }
 }