diff options
4 files changed, 138 insertions, 7 deletions
diff --git a/src/librustc_typeck/check/method/suggest.rs b/src/librustc_typeck/check/method/suggest.rs index 3cf9a1a9456..6f64374ea4a 100644 --- a/src/librustc_typeck/check/method/suggest.rs +++ b/src/librustc_typeck/check/method/suggest.rs @@ -34,6 +34,11 @@ pub fn report_error<'a, 'tcx>(fcx: &FnCtxt<'a, 'tcx>, method_name: ast::Name, error: MethodError) { + // avoid suggestions when we don't know what's going on. + if ty::type_is_error(rcvr_ty) { + return + } + match error { MethodError::NoMatch(static_sources, out_of_scope_traits) => { let cx = fcx.tcx(); @@ -135,7 +140,7 @@ pub type AllTraitsVec = Vec<TraitInfo>; fn suggest_traits_to_import<'a, 'tcx>(fcx: &FnCtxt<'a, 'tcx>, span: Span, - _rcvr_ty: Ty<'tcx>, + rcvr_ty: Ty<'tcx>, method_name: ast::Name, valid_out_of_scope_traits: Vec<ast::DefId>) { @@ -165,9 +170,22 @@ fn suggest_traits_to_import<'a, 'tcx>(fcx: &FnCtxt<'a, 'tcx>, return } - // there's no implemented traits, so lets suggest some traits to implement + let type_is_local = type_derefs_to_local(fcx, span, rcvr_ty); + + // there's no implemented traits, so lets suggest some traits to + // implement, by finding ones that have the method name, and are + // legal to implement. let mut candidates = all_traits(fcx.ccx) - .filter(|info| trait_method(tcx, info.def_id, method_name).is_some()) + .filter(|info| { + // we approximate the coherence rules to only suggest + // traits that are legal to implement by requiring that + // either the type or trait is local. Multidispatch means + // this isn't perfect (that is, there are cases when + // implementing a trait would be legal but is rejected + // here). + (type_is_local || ast_util::is_local(info.def_id)) + && trait_method(tcx, info.def_id, method_name).is_some() + }) .collect::<Vec<_>>(); if candidates.len() > 0 { @@ -175,6 +193,9 @@ fn suggest_traits_to_import<'a, 'tcx>(fcx: &FnCtxt<'a, 'tcx>, candidates.sort_by(|a, b| a.cmp(b).reverse()); candidates.dedup(); + // FIXME #21673 this help message could be tuned to the case + // of a type parameter: suggest adding a trait bound rather + // than implementing. let msg = format!( "methods from traits can only be called if the trait is implemented and in scope; \ the following {traits_define} a method `{name}`, \ @@ -194,6 +215,39 @@ fn suggest_traits_to_import<'a, 'tcx>(fcx: &FnCtxt<'a, 'tcx>, } } +/// Checks whether there is a local type somewhere in the chain of +/// autoderefs of `rcvr_ty`. +fn type_derefs_to_local<'a, 'tcx>(fcx: &FnCtxt<'a, 'tcx>, + span: Span, + rcvr_ty: Ty<'tcx>) -> bool { + check::autoderef(fcx, span, rcvr_ty, None, + check::UnresolvedTypeAction::Ignore, check::NoPreference, + |&: ty, _| { + let is_local = match ty.sty { + ty::ty_enum(did, _) | ty::ty_struct(did, _) => ast_util::is_local(did), + + ty::ty_trait(ref tr) => ast_util::is_local(tr.principal_def_id()), + + ty::ty_param(_) => true, + + // the user cannot implement traits for unboxed closures, so + // there's no point suggesting anything at all, local or not. + ty::ty_closure(..) => return Some(false), + + // everything else (primitive types etc.) is effectively + // non-local (there are "edge" cases, e.g. (LocalType,), but + // the noise from these sort of types is usually just really + // annoying, rather than any sort of help). + _ => false + }; + if is_local { + Some(true) + } else { + None + } + }).2.unwrap_or(false) +} + #[derive(Copy)] pub struct TraitInfo { pub def_id: ast::DefId, diff --git a/src/test/auxiliary/no_method_suggested_traits.rs b/src/test/auxiliary/no_method_suggested_traits.rs index 328561495ee..20cebb9be17 100644 --- a/src/test/auxiliary/no_method_suggested_traits.rs +++ b/src/test/auxiliary/no_method_suggested_traits.rs @@ -10,6 +10,9 @@ pub use reexport::Reexported; +pub struct Foo; +pub enum Bar { X } + pub mod foo { pub trait PubPub { fn method(&self) {} diff --git a/src/test/compile-fail/method-suggestion-no-duplication.rs b/src/test/compile-fail/method-suggestion-no-duplication.rs index 627fc6f0b05..e807d2b9448 100644 --- a/src/test/compile-fail/method-suggestion-no-duplication.rs +++ b/src/test/compile-fail/method-suggestion-no-duplication.rs @@ -10,7 +10,9 @@ // issue #21405 -fn foo<F>(f: F) where F: FnMut(usize) {} +struct Foo; + +fn foo<F>(f: F) where F: FnMut(Foo) {} fn main() { foo(|s| s.is_empty()); diff --git a/src/test/compile-fail/no-method-suggested-traits.rs b/src/test/compile-fail/no-method-suggested-traits.rs index ba8121eb5cc..2c14dfad3b8 100644 --- a/src/test/compile-fail/no-method-suggested-traits.rs +++ b/src/test/compile-fail/no-method-suggested-traits.rs @@ -12,6 +12,9 @@ extern crate no_method_suggested_traits; +struct Foo; +enum Bar { X } + mod foo { trait Bar { fn method(&self) {} @@ -25,23 +28,48 @@ mod foo { } fn main() { + // test the values themselves, and autoderef. + + 1u32.method(); //~^ HELP following traits are implemented but not in scope, perhaps add a `use` for one of them //~^^ ERROR does not implement //~^^^ HELP `foo::Bar` //~^^^^ HELP `no_method_suggested_traits::foo::PubPub` + std::rc::Rc::new(&mut Box::new(&1u32)).method(); + //~^ HELP following traits are implemented but not in scope, perhaps add a `use` for one of them + //~^^ ERROR does not implement + //~^^^ HELP `foo::Bar` + //~^^^^ HELP `no_method_suggested_traits::foo::PubPub` 'a'.method(); //~^ ERROR does not implement //~^^ HELP the following trait is implemented but not in scope, perhaps add a `use` for it: //~^^^ HELP `foo::Bar` + std::rc::Rc::new(&mut Box::new(&'a')).method(); + //~^ ERROR does not implement + //~^^ HELP the following trait is implemented but not in scope, perhaps add a `use` for it: + //~^^^ HELP `foo::Bar` 1i32.method(); //~^ ERROR does not implement //~^^ HELP the following trait is implemented but not in scope, perhaps add a `use` for it: //~^^^ HELP `no_method_suggested_traits::foo::PubPub` + std::rc::Rc::new(&mut Box::new(&1i32)).method(); + //~^ ERROR does not implement + //~^^ HELP the following trait is implemented but not in scope, perhaps add a `use` for it: + //~^^^ HELP `no_method_suggested_traits::foo::PubPub` - 1u64.method(); + Foo.method(); + //~^ ERROR does not implement + //~^^ HELP following traits define a method `method`, perhaps you need to implement one of them + //~^^^ HELP `foo::Bar` + //~^^^^ HELP `no_method_suggested_traits::foo::PubPub` + //~^^^^^ HELP `no_method_suggested_traits::reexport::Reexported` + //~^^^^^^ HELP `no_method_suggested_traits::bar::PubPriv` + //~^^^^^^^ HELP `no_method_suggested_traits::qux::PrivPub` + //~^^^^^^^^ HELP `no_method_suggested_traits::quz::PrivPriv` + std::rc::Rc::new(&mut Box::new(&Foo)).method(); //~^ ERROR does not implement //~^^ HELP following traits define a method `method`, perhaps you need to implement one of them //~^^^ HELP `foo::Bar` @@ -55,8 +83,52 @@ fn main() { //~^ ERROR does not implement //~^^ HELP the following trait defines a method `method2`, perhaps you need to implement it //~^^^ HELP `foo::Bar` - 1u64.method3(); + std::rc::Rc::new(&mut Box::new(&1u64)).method2(); //~^ ERROR does not implement - //~^^ HELP the following trait defines a method `method3`, perhaps you need to implement it + //~^^ HELP the following trait defines a method `method2`, perhaps you need to implement it + //~^^^ HELP `foo::Bar` + + no_method_suggested_traits::Foo.method2(); + //~^ ERROR does not implement + //~^^ HELP following trait defines a method `method2`, perhaps you need to implement it + //~^^^ HELP `foo::Bar` + std::rc::Rc::new(&mut Box::new(&no_method_suggested_traits::Foo)).method2(); + //~^ ERROR does not implement + //~^^ HELP following trait defines a method `method2`, perhaps you need to implement it + //~^^^ HELP `foo::Bar` + no_method_suggested_traits::Bar::X.method2(); + //~^ ERROR does not implement + //~^^ HELP following trait defines a method `method2`, perhaps you need to implement it + //~^^^ HELP `foo::Bar` + std::rc::Rc::new(&mut Box::new(&no_method_suggested_traits::Bar::X)).method2(); + //~^ ERROR does not implement + //~^^ HELP following trait defines a method `method2`, perhaps you need to implement it + //~^^^ HELP `foo::Bar` + + Foo.method3(); + //~^ ERROR does not implement + //~^^ HELP following trait defines a method `method3`, perhaps you need to implement it + //~^^^ HELP `no_method_suggested_traits::foo::PubPub` + std::rc::Rc::new(&mut Box::new(&Foo)).method3(); + //~^ ERROR does not implement + //~^^ HELP following trait defines a method `method3`, perhaps you need to implement it + //~^^^ HELP `no_method_suggested_traits::foo::PubPub` + Bar::X.method3(); + //~^ ERROR does not implement + //~^^ HELP following trait defines a method `method3`, perhaps you need to implement it //~^^^ HELP `no_method_suggested_traits::foo::PubPub` + std::rc::Rc::new(&mut Box::new(&Bar::X)).method3(); + //~^ ERROR does not implement + //~^^ HELP following trait defines a method `method3`, perhaps you need to implement it + //~^^^ HELP `no_method_suggested_traits::foo::PubPub` + + // should have no help: + 1us.method3(); //~ ERROR does not implement + std::rc::Rc::new(&mut Box::new(&1us)).method3(); //~ ERROR does not implement + no_method_suggested_traits::Foo.method3(); //~ ERROR does not implement + std::rc::Rc::new(&mut Box::new(&no_method_suggested_traits::Foo)).method3(); + //~^ ERROR does not implement + no_method_suggested_traits::Bar::X.method3(); //~ ERROR does not implement + std::rc::Rc::new(&mut Box::new(&no_method_suggested_traits::Bar::X)).method3(); + //~^ ERROR does not implement } |