Do precise capturing arg validation in resolve

Author: compiler-errors

Diff for: compiler/rustc_hir_analysis/src/collect/resolve_bound_vars.rs

@@ -584,7 +584,6 @@ impl<'a, 'tcx> Visitor<'tcx> for BoundVarContext<'a, 'tcx> {
                 | Res::SelfTyParam { trait_: def_id } => {
                     self.resolve_type_ref(def_id.expect_local(), param.hir_id);
                 }
-                Res::Err => {}
                 Res::SelfTyAlias { alias_to, .. } => {
                     self.tcx.dcx().emit_err(errors::PreciseCaptureSelfAlias {
                         span: param.ident.span,
@@ -593,11 +592,10 @@ impl<'a, 'tcx> Visitor<'tcx> for BoundVarContext<'a, 'tcx> {
                     });
                 }
                 res => {
-                    self.tcx.dcx().emit_err(errors::BadPreciseCapture {
-                        span: param.ident.span,
-                        kind: "type or const",
-                        found: res.descr().to_string(),
-                    });
+                    self.tcx.dcx().span_delayed_bug(
+                        param.ident.span,
+                        format!("expected type or const param, found {res:?}"),
+                    );
                 }
             },
         }

Diff for: compiler/rustc_resolve/src/late.rs

@@ -402,6 +402,8 @@ pub(crate) enum PathSource<'a> {
     TraitItem(Namespace),
     // Paths in delegation item
     Delegation,
+    /// An arg in a `use<'a, N>` precise-capturing bound.
+    PreciseCapturingArg(Namespace),
 }
 
 impl<'a> PathSource<'a> {
@@ -413,6 +415,7 @@ impl<'a> PathSource<'a> {
             | PathSource::TupleStruct(..)
             | PathSource::Delegation => ValueNS,
             PathSource::TraitItem(ns) => ns,
+            PathSource::PreciseCapturingArg(ns) => ns,
         }
     }
 
@@ -423,7 +426,10 @@ impl<'a> PathSource<'a> {
             | PathSource::Pat
             | PathSource::Struct
             | PathSource::TupleStruct(..) => true,
-            PathSource::Trait(_) | PathSource::TraitItem(..) | PathSource::Delegation => false,
+            PathSource::Trait(_)
+            | PathSource::TraitItem(..)
+            | PathSource::Delegation
+            | PathSource::PreciseCapturingArg(..) => false,
         }
     }
 
@@ -466,6 +472,7 @@ impl<'a> PathSource<'a> {
                 _ => "value",
             },
             PathSource::Delegation => "function",
+            PathSource::PreciseCapturingArg(..) => "type or const parameter",
         }
     }
 
@@ -534,15 +541,25 @@ impl<'a> PathSource<'a> {
                 _ => false,
             },
             PathSource::Delegation => matches!(res, Res::Def(DefKind::Fn | DefKind::AssocFn, _)),
+            PathSource::PreciseCapturingArg(ValueNS) => {
+                matches!(res, Res::Def(DefKind::ConstParam, _))
+            }
+            // We allow `SelfTyAlias` here so we can give a more descriptive error later.
+            PathSource::PreciseCapturingArg(TypeNS) => matches!(
+                res,
+                Res::Def(DefKind::TyParam, _) | Res::SelfTyParam { .. } | Res::SelfTyAlias { .. }
+            ),
+            PathSource::PreciseCapturingArg(MacroNS) => false,
         }
     }
 
     fn error_code(self, has_unexpected_resolution: bool) -> ErrCode {
         match (self, has_unexpected_resolution) {
             (PathSource::Trait(_), true) => E0404,
             (PathSource::Trait(_), false) => E0405,
-            (PathSource::Type, true) => E0573,
-            (PathSource::Type, false) => E0412,
+            // TODO:
+            (PathSource::Type | PathSource::PreciseCapturingArg(..), true) => E0573,
+            (PathSource::Type | PathSource::PreciseCapturingArg(..), false) => E0412,
             (PathSource::Struct, true) => E0574,
             (PathSource::Struct, false) => E0422,
             (PathSource::Expr(..), true) | (PathSource::Delegation, true) => E0423,
@@ -1077,9 +1094,19 @@ impl<'ra: 'ast, 'ast, 'tcx> Visitor<'ast> for LateResolutionVisitor<'_, 'ast, 'r
                 };
                 // Like `Ty::Param`, we try resolving this as both a const and a type.
                 if !check_ns(TypeNS) && check_ns(ValueNS) {
-                    self.smart_resolve_path(*id, &None, path, PathSource::Expr(None));
+                    self.smart_resolve_path(
+                        *id,
+                        &None,
+                        path,
+                        PathSource::PreciseCapturingArg(ValueNS),
+                    );
                 } else {
-                    self.smart_resolve_path(*id, &None, path, PathSource::Type);
+                    self.smart_resolve_path(
+                        *id,
+                        &None,
+                        path,
+                        PathSource::PreciseCapturingArg(TypeNS),
+                    );
                 }
             }
         }
@@ -1889,7 +1916,10 @@ impl<'a, 'ast, 'ra: 'ast, 'tcx> LateResolutionVisitor<'a, 'ast, 'ra, 'tcx> {
             );
 
             let inferred = match source {
-                PathSource::Trait(..) | PathSource::TraitItem(..) | PathSource::Type => false,
+                PathSource::Trait(..)
+                | PathSource::TraitItem(..)
+                | PathSource::Type
+                | PathSource::PreciseCapturingArg(..) => false,
                 PathSource::Expr(..)
                 | PathSource::Pat
                 | PathSource::Struct
@@ -3982,7 +4012,9 @@ impl<'a, 'ast, 'ra: 'ast, 'tcx> LateResolutionVisitor<'a, 'ast, 'ra, 'tcx> {
                         Applicability::MaybeIncorrect,
                     ))
                 } else if res.is_none()
-                    && let PathSource::Type | PathSource::Expr(_) = source
+                    && let PathSource::Type
+                    | PathSource::Expr(_)
+                    | PathSource::PreciseCapturingArg(..) = source
                 {
                     this.suggest_adding_generic_parameter(path, source)
                 } else {

Diff for: compiler/rustc_resolve/src/late/diagnostics.rs

@@ -2538,8 +2538,13 @@ impl<'ast, 'ra: 'ast, 'tcx> LateResolutionVisitor<'_, 'ast, 'ra, 'tcx> {
                     }
 
                     let (msg, sugg) = match source {
-                        PathSource::Type => ("you might be missing a type parameter", ident),
-                        PathSource::Expr(_) => ("you might be missing a const parameter", format!("const {ident}: /* Type */")),
+                        PathSource::Type | PathSource::PreciseCapturingArg(TypeNS) => {
+                            ("you might be missing a type parameter", ident)
+                        }
+                        PathSource::Expr(_) | PathSource::PreciseCapturingArg(ValueNS) => (
+                            "you might be missing a const parameter",
+                            format!("const {ident}: /* Type */"),
+                        ),
                         _ => return None,
                     };
                     let (span, sugg) = if let [.., param] = &generics.params[..] {

Diff for: tests/crashes/130399.rs

@@ -1,8 +1,8 @@
 fn missing() -> impl Sized + use<T> {}
-//~^ ERROR cannot find type `T` in this scope
+//~^ ERROR cannot find type or const parameter `T` in this scope
 
 fn missing_self() -> impl Sized + use<Self> {}
-//~^ ERROR cannot find type `Self` in this scope
+//~^ ERROR cannot find type or const parameter `Self` in this scope
 
 struct MyType;
 impl MyType {
@@ -11,6 +11,9 @@ impl MyType {
 }
 
 fn hello() -> impl Sized + use<hello> {}
-//~^ ERROR expected type or const parameter in `use<...>` precise captures list, found function
+//~^ ERROR expected type or const parameter, found function `hello`
+
+fn arg(x: ()) -> impl Sized + use<x> {}
+//~^ ERROR expected type or const parameter, found local variable `x`
 
 fn main() {}

Diff for: tests/ui/impl-trait/precise-capturing/bad-params.rs

@@ -1,4 +1,4 @@
-error[E0412]: cannot find type `T` in this scope
+error[E0412]: cannot find type or const parameter `T` in this scope
   --> $DIR/bad-params.rs:1:34
    |
 LL | fn missing() -> impl Sized + use<T> {}
@@ -9,14 +9,26 @@ help: you might be missing a type parameter
 LL | fn missing<T>() -> impl Sized + use<T> {}
    |           +++
 
-error[E0411]: cannot find type `Self` in this scope
+error[E0411]: cannot find type or const parameter `Self` in this scope
   --> $DIR/bad-params.rs:4:39
    |
 LL | fn missing_self() -> impl Sized + use<Self> {}
    |    ------------                       ^^^^ `Self` is only available in impls, traits, and type definitions
    |    |
    |    `Self` not allowed in a function
 
+error[E0573]: expected type or const parameter, found function `hello`
+  --> $DIR/bad-params.rs:13:32
+   |
+LL | fn hello() -> impl Sized + use<hello> {}
+   |                                ^^^^^ not a type or const parameter
+
+error[E0573]: expected type or const parameter, found local variable `x`
+  --> $DIR/bad-params.rs:16:35
+   |
+LL | fn arg(x: ()) -> impl Sized + use<x> {}
+   |                                   ^ not a type or const parameter
+
 error: `Self` can't be captured in `use<...>` precise captures list, since it is an alias
   --> $DIR/bad-params.rs:9:48
    |
@@ -25,13 +37,7 @@ LL | impl MyType {
 LL |     fn self_is_not_param() -> impl Sized + use<Self> {}
    |                                                ^^^^
 
-error: expected type or const parameter in `use<...>` precise captures list, found function
-  --> $DIR/bad-params.rs:13:32
-   |
-LL | fn hello() -> impl Sized + use<hello> {}
-   |                                ^^^^^
-
-error: aborting due to 4 previous errors
+error: aborting due to 5 previous errors
 
-Some errors have detailed explanations: E0411, E0412.
+Some errors have detailed explanations: E0411, E0412, E0573.
 For more information about an error, try `rustc --explain E0411`.