Use more detailed spans in dyn compat errors within bodies

Author: oli-obk

compiler/rustc_hir_analysis/src/collect.rs

@@ -31,7 +31,7 @@ use rustc_hir::def_id::{DefId, LocalDefId};
 use rustc_hir::intravisit::{self, InferKind, Visitor, VisitorExt, walk_generics};
 use rustc_hir::{self as hir, GenericParamKind, HirId, Node, PreciseCapturingArgKind};
 use rustc_infer::infer::{InferCtxt, TyCtxtInferExt};
-use rustc_infer::traits::ObligationCause;
+use rustc_infer::traits::{DynCompatibilityViolation, ObligationCause};
 use rustc_middle::hir::nested_filter;
 use rustc_middle::query::Providers;
 use rustc_middle::ty::util::{Discr, IntTypeExt};
@@ -40,7 +40,7 @@ use rustc_middle::{bug, span_bug};
 use rustc_span::{DUMMY_SP, Ident, Span, Symbol, kw, sym};
 use rustc_trait_selection::error_reporting::traits::suggestions::NextTypeParamName;
 use rustc_trait_selection::infer::InferCtxtExt;
-use rustc_trait_selection::traits::ObligationCtxt;
+use rustc_trait_selection::traits::{ObligationCtxt, hir_ty_lowering_dyn_compatibility_violations};
 use tracing::{debug, instrument};
 
 use crate::errors;
@@ -626,6 +626,10 @@ impl<'tcx> HirTyLowerer<'tcx> for ItemCtxt<'tcx> {
 
         (input_tys, output_ty)
     }
+
+    fn dyn_compatibility_violations(&self, trait_def_id: DefId) -> Vec<DynCompatibilityViolation> {
+        hir_ty_lowering_dyn_compatibility_violations(self.tcx, trait_def_id)
+    }
 }
 
 /// Synthesize a new lifetime name that doesn't clash with any of the lifetimes already present.

compiler/rustc_hir_analysis/src/hir_ty_lowering/dyn_compatibility.rs

@@ -11,7 +11,7 @@ use rustc_middle::ty::{
 };
 use rustc_span::{ErrorGuaranteed, Span};
 use rustc_trait_selection::error_reporting::traits::report_dyn_incompatibility;
-use rustc_trait_selection::traits::{self, hir_ty_lowering_dyn_compatibility_violations};
+use rustc_trait_selection::traits;
 use smallvec::{SmallVec, smallvec};
 use tracing::{debug, instrument};
 
@@ -99,8 +99,7 @@ impl<'tcx> dyn HirTyLowerer<'tcx> + '_ {
         // to avoid ICEs.
         for (clause, span) in user_written_bounds {
             if let Some(trait_pred) = clause.as_trait_clause() {
-                let violations =
-                    hir_ty_lowering_dyn_compatibility_violations(tcx, trait_pred.def_id());
+                let violations = self.dyn_compatibility_violations(trait_pred.def_id());
                 if !violations.is_empty() {
                     let reported = report_dyn_incompatibility(
                         tcx,

compiler/rustc_hir_analysis/src/hir_ty_lowering/mod.rs

@@ -33,7 +33,7 @@ use rustc_hir::def::{CtorKind, CtorOf, DefKind, Res};
 use rustc_hir::def_id::{DefId, LocalDefId};
 use rustc_hir::{self as hir, AnonConst, GenericArg, GenericArgs, HirId};
 use rustc_infer::infer::{InferCtxt, TyCtxtInferExt};
-use rustc_infer::traits::ObligationCause;
+use rustc_infer::traits::{DynCompatibilityViolation, ObligationCause};
 use rustc_middle::middle::stability::AllowUnstable;
 use rustc_middle::mir::interpret::LitToConstInput;
 use rustc_middle::ty::print::PrintPolyTraitRefExt as _;
@@ -203,6 +203,10 @@ pub trait HirTyLowerer<'tcx> {
     {
         self
     }
+
+    /// Performs minimalistic dyn compat checks outside of bodies, but full within bodies.
+    /// Outside of bodies we could end up in cycles, so we delay most checks to later phases.
+    fn dyn_compatibility_violations(&self, trait_def_id: DefId) -> Vec<DynCompatibilityViolation>;
 }
 
 /// The "qualified self" of an associated item path.

compiler/rustc_hir_typeck/src/fn_ctxt/mod.rs

@@ -14,7 +14,7 @@ use rustc_hir::def_id::{DefId, LocalDefId};
 use rustc_hir::{self as hir, HirId, ItemLocalMap};
 use rustc_hir_analysis::hir_ty_lowering::{HirTyLowerer, RegionInferReason};
 use rustc_infer::infer;
-use rustc_infer::traits::Obligation;
+use rustc_infer::traits::{DynCompatibilityViolation, Obligation};
 use rustc_middle::ty::{self, Const, Ty, TyCtxt, TypeVisitableExt};
 use rustc_session::Session;
 use rustc_span::{self, DUMMY_SP, ErrorGuaranteed, Ident, Span, sym};
@@ -389,6 +389,10 @@ impl<'tcx> HirTyLowerer<'tcx> for FnCtxt<'_, 'tcx> {
         };
         (input_tys, output_ty)
     }
+
+    fn dyn_compatibility_violations(&self, trait_def_id: DefId) -> Vec<DynCompatibilityViolation> {
+        self.tcx.dyn_compatibility_violations(trait_def_id).to_vec()
+    }
 }
 
 /// The `ty` representation of a user-provided type. Depending on the use-site

tests/ui/async-await/dyn/mut-is-pointer-like.stderr

@@ -8,10 +8,10 @@ LL | #![feature(async_fn_in_dyn_trait)]
    = note: `#[warn(incomplete_features)]` on by default
 
 error[E0038]: the trait `AsyncTrait` is not dyn compatible
-  --> $DIR/mut-is-pointer-like.rs:35:16
+  --> $DIR/mut-is-pointer-like.rs:35:29
    |
 LL |         let x: Pin<&mut dyn AsyncTrait<Output = ()>> = f;
-   |                ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ `AsyncTrait` is not dyn compatible
+   |                             ^^^^^^^^^^^^^^^^^^^^^^^ `AsyncTrait` is not dyn compatible
    |
 note: for a trait to be dyn compatible it needs to allow building a vtable
       for more information, visit <https://doc.rust-lang.org/reference/items/traits.html#dyn-compatibility>
@@ -24,48 +24,6 @@ LL |     async fn async_dispatch(self: Pin<&mut Self>) -> Self::Output;
    |              ^^^^^^^^^^^^^^ ...because method `async_dispatch` is `async`
    = help: consider moving `async_dispatch` to another trait
 
-error[E0038]: the trait `AsyncTrait` is not dyn compatible
-  --> $DIR/mut-is-pointer-like.rs:35:56
-   |
-LL |         let x: Pin<&mut dyn AsyncTrait<Output = ()>> = f;
-   |                                                        ^ `AsyncTrait` is not dyn compatible
-   |
-note: for a trait to be dyn compatible it needs to allow building a vtable
-      for more information, visit <https://doc.rust-lang.org/reference/items/traits.html#dyn-compatibility>
-  --> $DIR/mut-is-pointer-like.rs:16:14
-   |
-LL | trait AsyncTrait {
-   |       ---------- this trait is not dyn compatible...
-...
-LL |     async fn async_dispatch(self: Pin<&mut Self>) -> Self::Output;
-   |              ^^^^^^^^^^^^^^ ...because method `async_dispatch` is `async`
-   = help: consider moving `async_dispatch` to another trait
-   = note: required for the cast from `Pin<&mut {async block@$DIR/mut-is-pointer-like.rs:32:32: 32:37}>` to `Pin<&mut dyn AsyncTrait<Output = ()>>`
-
-error[E0277]: the trait bound `dyn AsyncTrait<Output = ()>: AsyncTrait` is not satisfied
-  --> $DIR/mut-is-pointer-like.rs:36:11
-   |
-LL |         x.async_dispatch().await;
-   |           ^^^^^^^^^^^^^^ the trait `AsyncTrait` is not implemented for `dyn AsyncTrait<Output = ()>`
-
-error[E0038]: the trait `AsyncTrait` is not dyn compatible
-  --> $DIR/mut-is-pointer-like.rs:36:9
-   |
-LL |         x.async_dispatch().await;
-   |         ^^^^^^^^^^^^^^^^^^ `AsyncTrait` is not dyn compatible
-   |
-note: for a trait to be dyn compatible it needs to allow building a vtable
-      for more information, visit <https://doc.rust-lang.org/reference/items/traits.html#dyn-compatibility>
-  --> $DIR/mut-is-pointer-like.rs:16:14
-   |
-LL | trait AsyncTrait {
-   |       ---------- this trait is not dyn compatible...
-...
-LL |     async fn async_dispatch(self: Pin<&mut Self>) -> Self::Output;
-   |              ^^^^^^^^^^^^^^ ...because method `async_dispatch` is `async`
-   = help: consider moving `async_dispatch` to another trait
-
-error: aborting due to 4 previous errors; 1 warning emitted
+error: aborting due to 1 previous error; 1 warning emitted
 
-Some errors have detailed explanations: E0038, E0277.
-For more information about an error, try `rustc --explain E0038`.
+For more information about this error, try `rustc --explain E0038`.

tests/ui/async-await/dyn/works.stderr

@@ -8,10 +8,10 @@ LL | #![feature(async_fn_in_dyn_trait)]
    = note: `#[warn(incomplete_features)]` on by default
 
 error[E0038]: the trait `AsyncTrait` is not dyn compatible
-  --> $DIR/works.rs:27:34
+  --> $DIR/works.rs:27:21
    |
 LL |         let x: &dyn AsyncTrait = &"hello, world!";
-   |                                  ^^^^^^^^^^^^^^^^ `AsyncTrait` is not dyn compatible
+   |                     ^^^^^^^^^^ `AsyncTrait` is not dyn compatible
    |
 note: for a trait to be dyn compatible it needs to allow building a vtable
       for more information, visit <https://doc.rust-lang.org/reference/items/traits.html#dyn-compatibility>
@@ -23,59 +23,7 @@ LL |     async fn async_dispatch(&self);
    |              ^^^^^^^^^^^^^^ ...because method `async_dispatch` is `async`
    = help: consider moving `async_dispatch` to another trait
    = help: only type `&'static str` implements `AsyncTrait`; consider using it directly instead.
-   = note: required for the cast from `&&'static str` to `&dyn AsyncTrait`
 
-error[E0038]: the trait `AsyncTrait` is not dyn compatible
-  --> $DIR/works.rs:27:16
-   |
-LL |         let x: &dyn AsyncTrait = &"hello, world!";
-   |                ^^^^^^^^^^^^^^^ `AsyncTrait` is not dyn compatible
-   |
-note: for a trait to be dyn compatible it needs to allow building a vtable
-      for more information, visit <https://doc.rust-lang.org/reference/items/traits.html#dyn-compatibility>
-  --> $DIR/works.rs:14:14
-   |
-LL | trait AsyncTrait {
-   |       ---------- this trait is not dyn compatible...
-LL |     async fn async_dispatch(&self);
-   |              ^^^^^^^^^^^^^^ ...because method `async_dispatch` is `async`
-   = help: consider moving `async_dispatch` to another trait
-   = help: only type `&'static str` implements `AsyncTrait`; consider using it directly instead.
-
-error[E0038]: the trait `AsyncTrait` is not dyn compatible
-  --> $DIR/works.rs:28:11
-   |
-LL |         x.async_dispatch().await;
-   |           ^^^^^^^^^^^^^^ `AsyncTrait` is not dyn compatible
-   |
-note: for a trait to be dyn compatible it needs to allow building a vtable
-      for more information, visit <https://doc.rust-lang.org/reference/items/traits.html#dyn-compatibility>
-  --> $DIR/works.rs:14:14
-   |
-LL | trait AsyncTrait {
-   |       ---------- this trait is not dyn compatible...
-LL |     async fn async_dispatch(&self);
-   |              ^^^^^^^^^^^^^^ ...because method `async_dispatch` is `async`
-   = help: consider moving `async_dispatch` to another trait
-   = help: only type `&'static str` implements `AsyncTrait`; consider using it directly instead.
-
-error[E0038]: the trait `AsyncTrait` is not dyn compatible
-  --> $DIR/works.rs:28:9
-   |
-LL |         x.async_dispatch().await;
-   |         ^^^^^^^^^^^^^^^^^^ `AsyncTrait` is not dyn compatible
-   |
-note: for a trait to be dyn compatible it needs to allow building a vtable
-      for more information, visit <https://doc.rust-lang.org/reference/items/traits.html#dyn-compatibility>
-  --> $DIR/works.rs:14:14
-   |
-LL | trait AsyncTrait {
-   |       ---------- this trait is not dyn compatible...
-LL |     async fn async_dispatch(&self);
-   |              ^^^^^^^^^^^^^^ ...because method `async_dispatch` is `async`
-   = help: consider moving `async_dispatch` to another trait
-   = help: only type `&'static str` implements `AsyncTrait`; consider using it directly instead.
-
-error: aborting due to 4 previous errors; 1 warning emitted
+error: aborting due to 1 previous error; 1 warning emitted
 
 For more information about this error, try `rustc --explain E0038`.

tests/ui/async-await/dyn/wrong-size.stderr

@@ -8,10 +8,10 @@ LL | #![feature(async_fn_in_dyn_trait)]
    = note: `#[warn(incomplete_features)]` on by default
 
 error[E0038]: the trait `AsyncTrait` is not dyn compatible
-  --> $DIR/wrong-size.rs:21:30
+  --> $DIR/wrong-size.rs:21:17
    |
 LL |     let x: &dyn AsyncTrait = &"hello, world!";
-   |                              ^^^^^^^^^^^^^^^^ `AsyncTrait` is not dyn compatible
+   |                 ^^^^^^^^^^ `AsyncTrait` is not dyn compatible
    |
 note: for a trait to be dyn compatible it needs to allow building a vtable
       for more information, visit <https://doc.rust-lang.org/reference/items/traits.html#dyn-compatibility>
@@ -23,25 +23,7 @@ LL |     async fn async_dispatch(&self);
    |              ^^^^^^^^^^^^^^ ...because method `async_dispatch` is `async`
    = help: consider moving `async_dispatch` to another trait
    = help: only type `&'static str` implements `AsyncTrait`; consider using it directly instead.
-   = note: required for the cast from `&&'static str` to `&dyn AsyncTrait`
 
-error[E0038]: the trait `AsyncTrait` is not dyn compatible
-  --> $DIR/wrong-size.rs:21:12
-   |
-LL |     let x: &dyn AsyncTrait = &"hello, world!";
-   |            ^^^^^^^^^^^^^^^ `AsyncTrait` is not dyn compatible
-   |
-note: for a trait to be dyn compatible it needs to allow building a vtable
-      for more information, visit <https://doc.rust-lang.org/reference/items/traits.html#dyn-compatibility>
-  --> $DIR/wrong-size.rs:9:14
-   |
-LL | trait AsyncTrait {
-   |       ---------- this trait is not dyn compatible...
-LL |     async fn async_dispatch(&self);
-   |              ^^^^^^^^^^^^^^ ...because method `async_dispatch` is `async`
-   = help: consider moving `async_dispatch` to another trait
-   = help: only type `&'static str` implements `AsyncTrait`; consider using it directly instead.
-
-error: aborting due to 2 previous errors; 1 warning emitted
+error: aborting due to 1 previous error; 1 warning emitted
 
 For more information about this error, try `rustc --explain E0038`.

tests/ui/async-await/in-trait/dyn-compatibility.stderr

@@ -1,8 +1,8 @@
 error[E0038]: the trait `Foo` is not dyn compatible
-  --> $DIR/dyn-compatibility.rs:9:12
+  --> $DIR/dyn-compatibility.rs:9:17
    |
 LL |     let x: &dyn Foo = todo!();
-   |            ^^^^^^^^ `Foo` is not dyn compatible
+   |                 ^^^ `Foo` is not dyn compatible
    |
 note: for a trait to be dyn compatible it needs to allow building a vtable
       for more information, visit <https://doc.rust-lang.org/reference/items/traits.html#dyn-compatibility>

tests/ui/did_you_mean/trait-object-reference-without-parens-suggestion.rs

@@ -4,4 +4,5 @@ fn main() {
     let _: &Copy + 'static; //~ ERROR expected a path
     //~^ ERROR is not dyn compatible
     let _: &'static Copy + 'static; //~ ERROR expected a path
+    //~^ ERROR is not dyn compatible
 }

tests/ui/did_you_mean/trait-object-reference-without-parens-suggestion.stderr

@@ -21,16 +21,26 @@ LL |     let _: &'static (Copy + 'static);
    |                     +              +
 
 error[E0038]: the trait `Copy` is not dyn compatible
-  --> $DIR/trait-object-reference-without-parens-suggestion.rs:4:12
+  --> $DIR/trait-object-reference-without-parens-suggestion.rs:4:13
    |
 LL |     let _: &Copy + 'static;
-   |            ^^^^^ `Copy` is not dyn compatible
+   |             ^^^^ `Copy` is not dyn compatible
+   |
+   = note: the trait is not dyn compatible because it requires `Self: Sized`
+   = note: for a trait to be dyn compatible it needs to allow building a vtable
+           for more information, visit <https://doc.rust-lang.org/reference/items/traits.html#dyn-compatibility>
+
+error[E0038]: the trait `Copy` is not dyn compatible
+  --> $DIR/trait-object-reference-without-parens-suggestion.rs:6:21
+   |
+LL |     let _: &'static Copy + 'static;
+   |                     ^^^^ `Copy` is not dyn compatible
    |
    = note: the trait is not dyn compatible because it requires `Self: Sized`
    = note: for a trait to be dyn compatible it needs to allow building a vtable
            for more information, visit <https://doc.rust-lang.org/reference/items/traits.html#dyn-compatibility>
 
-error: aborting due to 3 previous errors
+error: aborting due to 4 previous errors
 
 Some errors have detailed explanations: E0038, E0178.
 For more information about an error, try `rustc --explain E0038`.