diff --git a/src/librustc/traits/error_reporting.rs b/src/librustc/traits/error_reporting.rs index 0144d51a9693f..00b575adbce0a 100644 --- a/src/librustc/traits/error_reporting.rs +++ b/src/librustc/traits/error_reporting.rs @@ -38,6 +38,7 @@ use std::fmt; use syntax::ast; use syntax::symbol::{sym, kw}; use syntax_pos::{DUMMY_SP, Span, ExpnKind, MultiSpan}; +use rustc::hir::def_id::LOCAL_CRATE; use rustc_error_codes::*; @@ -799,6 +800,7 @@ impl<'a, 'tcx> InferCtxt<'a, 'tcx> { self.suggest_fn_call(&obligation, &mut err, &trait_ref, points_at_arg); self.suggest_remove_reference(&obligation, &mut err, &trait_ref); self.suggest_semicolon_removal(&obligation, &mut err, span, &trait_ref); + self.note_version_mismatch(&mut err, &trait_ref); // Try to report a help message if !trait_ref.has_infer_types() && @@ -1050,6 +1052,43 @@ impl<'a, 'tcx> InferCtxt<'a, 'tcx> { err.emit(); } + /// If the `Self` type of the unsatisfied trait `trait_ref` implements a trait + /// with the same path as `trait_ref`, a help message about + /// a probable version mismatch is added to `err` + fn note_version_mismatch( + &self, + err: &mut DiagnosticBuilder<'_>, + trait_ref: &ty::PolyTraitRef<'tcx>, + ) { + let get_trait_impl = |trait_def_id| { + let mut trait_impl = None; + self.tcx.for_each_relevant_impl(trait_def_id, trait_ref.self_ty(), |impl_def_id| { + if trait_impl.is_none() { + trait_impl = Some(impl_def_id); + } + }); + trait_impl + }; + let required_trait_path = self.tcx.def_path_str(trait_ref.def_id()); + let all_traits = self.tcx.all_traits(LOCAL_CRATE); + let traits_with_same_path: std::collections::BTreeSet<_> = all_traits + .iter() + .filter(|trait_def_id| **trait_def_id != trait_ref.def_id()) + .filter(|trait_def_id| self.tcx.def_path_str(**trait_def_id) == required_trait_path) + .collect(); + for trait_with_same_path in traits_with_same_path { + if let Some(impl_def_id) = get_trait_impl(*trait_with_same_path) { + let impl_span = self.tcx.def_span(impl_def_id); + err.span_help(impl_span, "Trait impl with same name found"); + let trait_crate = self.tcx.crate_name(trait_with_same_path.krate); + let crate_msg = format!( + "Perhaps two different versions of crate `{}` are being used?", + trait_crate + ); + err.note(&crate_msg); + } + } + } fn suggest_restricting_param_bound( &self, err: &mut DiagnosticBuilder<'_>, diff --git a/src/test/ui/traits/auxiliary/crate_a1.rs b/src/test/ui/traits/auxiliary/crate_a1.rs index e2e18500541ef..724206860fe50 100644 --- a/src/test/ui/traits/auxiliary/crate_a1.rs +++ b/src/test/ui/traits/auxiliary/crate_a1.rs @@ -2,10 +2,4 @@ pub struct Foo; pub trait Bar{} -pub fn bar() -> Box { - unimplemented!() -} - - -pub fn try_foo(x: Foo){} -pub fn try_bar(x: Box){} +pub fn try_foo(x: impl Bar){} diff --git a/src/test/ui/traits/auxiliary/crate_a2.rs b/src/test/ui/traits/auxiliary/crate_a2.rs new file mode 100644 index 0000000000000..d8a178dc0d90e --- /dev/null +++ b/src/test/ui/traits/auxiliary/crate_a2.rs @@ -0,0 +1,5 @@ +pub struct Foo; + +pub trait Bar{} + +impl Bar for Foo {} diff --git a/src/test/ui/traits/trait-bounds-same-crate-name.rs b/src/test/ui/traits/trait-bounds-same-crate-name.rs new file mode 100644 index 0000000000000..2ef1c989a5661 --- /dev/null +++ b/src/test/ui/traits/trait-bounds-same-crate-name.rs @@ -0,0 +1,21 @@ +// aux-build:crate_a1.rs +// aux-build:crate_a2.rs + +// Issue 22750 +// This tests the extra help message reported when a trait bound +// is not met but the struct implements a trait with the same path. + +fn main() { + let foo2 = { + extern crate crate_a2 as a; + a::Foo + }; + + { + extern crate crate_a1 as a; + a::try_foo(foo2); + //~^ ERROR E0277 + //~| Trait impl with same name found + //~| Perhaps two different versions of crate `crate_a2` + } +} diff --git a/src/test/ui/traits/trait-bounds-same-crate-name.stderr b/src/test/ui/traits/trait-bounds-same-crate-name.stderr new file mode 100644 index 0000000000000..78ea9a849f437 --- /dev/null +++ b/src/test/ui/traits/trait-bounds-same-crate-name.stderr @@ -0,0 +1,21 @@ +error[E0277]: the trait bound `main::a::Foo: main::a::Bar` is not satisfied + --> $DIR/trait-bounds-same-crate-name.rs:16:20 + | +LL | a::try_foo(foo2); + | ^^^^ the trait `main::a::Bar` is not implemented for `main::a::Foo` + | + ::: $DIR/auxiliary/crate_a1.rs:5:24 + | +LL | pub fn try_foo(x: impl Bar){} + | --- required by this bound in `main::a::try_foo` + | +help: Trait impl with same name found + --> $DIR/auxiliary/crate_a2.rs:5:1 + | +LL | impl Bar for Foo {} + | ^^^^^^^^^^^^^^^^^^^ + = note: Perhaps two different versions of crate `crate_a2` are being used? + +error: aborting due to previous error + +For more information about this error, try `rustc --explain E0277`.