Explicitly mention Self

compiler/rustc_hir_analysis/messages.ftl

@@ -351,7 +351,7 @@ hir_analysis_param_in_ty_of_assoc_const_binding =
         *[normal] the {$param_def_kind} `{$param_name}` is defined here
     }
 
-hir_analysis_param_not_captured = `impl Trait` must mention all {$kind} parameters in scope
+hir_analysis_param_not_captured = `impl Trait` must mention all {$kind} parameters in scope in `use<...>`
     .label = {$kind} parameter is implicitly captured by this `impl Trait`
     .note = currently, all {$kind} parameters are required to be mentioned in the precise captures list
 
@@ -405,6 +405,10 @@ hir_analysis_self_in_impl_self =
     `Self` is not valid in the self type of an impl block
     .note = replace `Self` with a different type
 
+hir_analysis_self_ty_not_captured = `impl Trait` must mention the `Self` type of the trait in `use<...>`
+    .label = `Self` type parameter is implicitly captured by this `impl Trait`
+    .note = currently, all type parameters are required to be mentioned in the precise captures list
+
 hir_analysis_simd_ffi_highly_experimental = use of SIMD type{$snip} in FFI is highly experimental and may result in invalid code
     .help = add `#![feature(simd_ffi)]` to the crate attributes to enable
 

compiler/rustc_hir_analysis/src/check/check.rs

@@ -612,12 +612,20 @@ fn check_opaque_precise_captures<'tcx>(tcx: TyCtxt<'tcx>, opaque_def_id: LocalDe
                     }
                 }
                 ty::GenericParamDefKind::Type { .. } => {
-                    // FIXME(precise_capturing): Structured suggestion for this would be useful
+                    if matches!(tcx.def_kind(param.def_id), DefKind::Trait | DefKind::TraitAlias) {
-                    tcx.dcx().emit_err(errors::ParamNotCaptured {
+                        // FIXME(precise_capturing): Structured suggestion for this would be useful
-                        param_span: tcx.def_span(param.def_id),
+                        tcx.dcx().emit_err(errors::SelfTyNotCaptured {
-                        opaque_span: tcx.def_span(opaque_def_id),
+                            trait_span: tcx.def_span(param.def_id),
-                        kind: "type",
+                            opaque_span: tcx.def_span(opaque_def_id),
-                    });
+                        });
+                    } else {
+                        // FIXME(precise_capturing): Structured suggestion for this would be useful
+                        tcx.dcx().emit_err(errors::ParamNotCaptured {
+                            param_span: tcx.def_span(param.def_id),
+                            opaque_span: tcx.def_span(opaque_def_id),
+                            kind: "type",
+                        });
+                    }
                 }
                 ty::GenericParamDefKind::Const { .. } => {
                     // FIXME(precise_capturing): Structured suggestion for this would be useful

compiler/rustc_hir_analysis/src/errors/precise_captures.rs

@@ -12,6 +12,16 @@ pub struct ParamNotCaptured {
     pub kind: &'static str,
 }
 
+#[derive(Diagnostic)]
+#[diag(hir_analysis_self_ty_not_captured)]
+#[note]
+pub struct SelfTyNotCaptured {
+    #[primary_span]
+    pub opaque_span: Span,
+    #[label]
+    pub trait_span: Span,
+}
+
 #[derive(Diagnostic)]
 #[diag(hir_analysis_lifetime_not_captured)]
 pub struct LifetimeNotCaptured {

tests/ui/impl-trait/precise-capturing/forgot-to-capture-const.stderr

@@ -7,7 +7,7 @@ LL | #![feature(precise_capturing)]
    = note: see issue #123432 <https://github.com/rust-lang/rust/issues/123432> for more information
    = note: `#[warn(incomplete_features)]` on by default
 
-error: `impl Trait` must mention all const parameters in scope
+error: `impl Trait` must mention all const parameters in scope in `use<...>`
   --> $DIR/forgot-to-capture-const.rs:4:34
    |
 LL | fn constant<const C: usize>() -> impl use<> Sized {}

tests/ui/impl-trait/precise-capturing/forgot-to-capture-type.rs

@@ -6,7 +6,7 @@ fn type_param<T>() -> impl use<> Sized {}
 
 trait Foo {
     fn bar() -> impl use<> Sized;
-    //~^ ERROR `impl Trait` must mention all type parameters in scope
+    //~^ ERROR `impl Trait` must mention the `Self` type of the trait
 }
 
 fn main() {}

tests/ui/impl-trait/precise-capturing/forgot-to-capture-type.stderr

@@ -7,7 +7,7 @@ LL | #![feature(precise_capturing)]
    = note: see issue #123432 <https://github.com/rust-lang/rust/issues/123432> for more information
    = note: `#[warn(incomplete_features)]` on by default
 
-error: `impl Trait` must mention all type parameters in scope
+error: `impl Trait` must mention all type parameters in scope in `use<...>`
   --> $DIR/forgot-to-capture-type.rs:4:23
    |
 LL | fn type_param<T>() -> impl use<> Sized {}
@@ -17,11 +17,11 @@ LL | fn type_param<T>() -> impl use<> Sized {}
    |
    = note: currently, all type parameters are required to be mentioned in the precise captures list
 
-error: `impl Trait` must mention all type parameters in scope
+error: `impl Trait` must mention the `Self` type of the trait in `use<...>`
   --> $DIR/forgot-to-capture-type.rs:8:17
    |
 LL | trait Foo {
-   | --------- type parameter is implicitly captured by this `impl Trait`
+   | --------- `Self` type parameter is implicitly captured by this `impl Trait`
 LL |     fn bar() -> impl use<> Sized;
    |                 ^^^^^^^^^^^^^^^^
    |