From ef68bf3929e5073e84b48fd76a689b071842d756 Mon Sep 17 00:00:00 2001 From: Donough Liu Date: Sat, 20 Jun 2020 18:30:12 +0800 Subject: [PATCH] Try to suggest dereferences when trait selection failed. --- .../traits/error_reporting/mod.rs | 1 + .../traits/error_reporting/suggestions.rs | 67 ++++++++++++++++++- ...trait-suggest-deferences-issue-39029.fixed | 18 +++++ .../trait-suggest-deferences-issue-39029.rs | 18 +++++ ...rait-suggest-deferences-issue-39029.stderr | 19 ++++++ ...trait-suggest-deferences-issue-62530.fixed | 15 +++++ .../trait-suggest-deferences-issue-62530.rs | 15 +++++ ...rait-suggest-deferences-issue-62530.stderr | 15 +++++ .../trait-suggest-deferences-multiple.fixed | 36 ++++++++++ .../trait-suggest-deferences-multiple.rs | 36 ++++++++++ .../trait-suggest-deferences-multiple.stderr | 15 +++++ 11 files changed, 254 insertions(+), 1 deletion(-) create mode 100644 src/test/ui/traits/trait-suggest-deferences-issue-39029.fixed create mode 100644 src/test/ui/traits/trait-suggest-deferences-issue-39029.rs create mode 100644 src/test/ui/traits/trait-suggest-deferences-issue-39029.stderr create mode 100644 src/test/ui/traits/trait-suggest-deferences-issue-62530.fixed create mode 100644 src/test/ui/traits/trait-suggest-deferences-issue-62530.rs create mode 100644 src/test/ui/traits/trait-suggest-deferences-issue-62530.stderr create mode 100644 src/test/ui/traits/trait-suggest-deferences-multiple.fixed create mode 100644 src/test/ui/traits/trait-suggest-deferences-multiple.rs create mode 100644 src/test/ui/traits/trait-suggest-deferences-multiple.stderr diff --git a/src/librustc_trait_selection/traits/error_reporting/mod.rs b/src/librustc_trait_selection/traits/error_reporting/mod.rs index 060877f80ade..fd0c1a54d27a 100644 --- a/src/librustc_trait_selection/traits/error_reporting/mod.rs +++ b/src/librustc_trait_selection/traits/error_reporting/mod.rs @@ -402,6 +402,7 @@ impl<'a, 'tcx> InferCtxtExt<'tcx> for InferCtxt<'a, 'tcx> { err.span_label(enclosing_scope_span, s.as_str()); } + self.suggest_dereferences(&obligation, &mut err, &trait_ref, points_at_arg); self.suggest_borrow_on_unsized_slice(&obligation.cause.code, &mut err); self.suggest_fn_call(&obligation, &mut err, &trait_ref, points_at_arg); self.suggest_remove_reference(&obligation, &mut err, &trait_ref); diff --git a/src/librustc_trait_selection/traits/error_reporting/suggestions.rs b/src/librustc_trait_selection/traits/error_reporting/suggestions.rs index dfd7dac72d8e..0c86e33884d6 100644 --- a/src/librustc_trait_selection/traits/error_reporting/suggestions.rs +++ b/src/librustc_trait_selection/traits/error_reporting/suggestions.rs @@ -3,6 +3,7 @@ use super::{ SelectionContext, }; +use crate::autoderef::Autoderef; use crate::infer::InferCtxt; use crate::traits::normalize_projection_type; @@ -13,11 +14,11 @@ use rustc_hir::def_id::DefId; use rustc_hir::intravisit::Visitor; use rustc_hir::lang_items; use rustc_hir::{AsyncGeneratorKind, GeneratorKind, Node}; -use rustc_middle::ty::TypeckTables; use rustc_middle::ty::{ self, suggest_constraining_type_param, AdtKind, DefIdTree, Infer, InferTy, ToPredicate, Ty, TyCtxt, TypeFoldable, WithConstness, }; +use rustc_middle::ty::{TypeAndMut, TypeckTables}; use rustc_span::symbol::{kw, sym, Ident, Symbol}; use rustc_span::{MultiSpan, Span, DUMMY_SP}; use std::fmt; @@ -48,6 +49,14 @@ pub trait InferCtxtExt<'tcx> { err: &mut DiagnosticBuilder<'_>, ); + fn suggest_dereferences( + &self, + obligation: &PredicateObligation<'tcx>, + err: &mut DiagnosticBuilder<'tcx>, + trait_ref: &ty::PolyTraitRef<'tcx>, + points_at_arg: bool, + ); + fn get_closure_name( &self, def_id: DefId, @@ -450,6 +459,62 @@ impl<'a, 'tcx> InferCtxtExt<'tcx> for InferCtxt<'a, 'tcx> { } } + /// When after several dereferencing, the reference satisfies the trait + /// binding. This function provides dereference suggestion for this + /// specific situation. + fn suggest_dereferences( + &self, + obligation: &PredicateObligation<'tcx>, + err: &mut DiagnosticBuilder<'tcx>, + trait_ref: &ty::PolyTraitRef<'tcx>, + points_at_arg: bool, + ) { + // It only make sense when suggesting dereferences for arguments + if !points_at_arg { + return; + } + let param_env = obligation.param_env; + let body_id = obligation.cause.body_id; + let span = obligation.cause.span; + let real_trait_ref = match &obligation.cause.code { + ObligationCauseCode::ImplDerivedObligation(cause) + | ObligationCauseCode::DerivedObligation(cause) + | ObligationCauseCode::BuiltinDerivedObligation(cause) => &cause.parent_trait_ref, + _ => trait_ref, + }; + let real_ty = match real_trait_ref.self_ty().no_bound_vars() { + Some(ty) => ty, + None => return, + }; + + if let ty::Ref(region, base_ty, mutbl) = real_ty.kind { + let mut autoderef = Autoderef::new(self, param_env, body_id, span, base_ty); + if let Some(steps) = autoderef.find_map(|(ty, steps)| { + // Re-add the `&` + let ty = self.tcx.mk_ref(region, TypeAndMut { ty, mutbl }); + let obligation = + self.mk_trait_obligation_with_new_self_ty(param_env, real_trait_ref, ty); + Some(steps).filter(|_| self.predicate_may_hold(&obligation)) + }) { + if steps > 0 { + if let Ok(src) = self.tcx.sess.source_map().span_to_snippet(span) { + // Don't care about `&mut` because `DerefMut` is used less + // often and user will not expect autoderef happens. + if src.starts_with("&") { + let derefs = "*".repeat(steps); + err.span_suggestion( + span, + "consider adding dereference here", + format!("&{}{}", derefs, &src[1..]), + Applicability::MachineApplicable, + ); + } + } + } + } + } + } + /// When encountering an assignment of an unsized trait, like `let x = ""[..];`, provide a /// suggestion to borrow the initializer in order to use have a slice instead. fn suggest_borrow_on_unsized_slice( diff --git a/src/test/ui/traits/trait-suggest-deferences-issue-39029.fixed b/src/test/ui/traits/trait-suggest-deferences-issue-39029.fixed new file mode 100644 index 000000000000..2bb34b0ebee6 --- /dev/null +++ b/src/test/ui/traits/trait-suggest-deferences-issue-39029.fixed @@ -0,0 +1,18 @@ +// run-rustfix +use std::net::TcpListener; + +struct NoToSocketAddrs(String); + +impl std::ops::Deref for NoToSocketAddrs { + type Target = String; + fn deref(&self) -> &Self::Target { + &self.0 + } +} + +fn main() { + let _works = TcpListener::bind("some string"); + let bad = NoToSocketAddrs("bad".to_owned()); + let _errors = TcpListener::bind(&*bad); + //~^ ERROR the trait bound `NoToSocketAddrs: std::net::ToSocketAddrs` is not satisfied +} diff --git a/src/test/ui/traits/trait-suggest-deferences-issue-39029.rs b/src/test/ui/traits/trait-suggest-deferences-issue-39029.rs new file mode 100644 index 000000000000..33d524608a05 --- /dev/null +++ b/src/test/ui/traits/trait-suggest-deferences-issue-39029.rs @@ -0,0 +1,18 @@ +// run-rustfix +use std::net::TcpListener; + +struct NoToSocketAddrs(String); + +impl std::ops::Deref for NoToSocketAddrs { + type Target = String; + fn deref(&self) -> &Self::Target { + &self.0 + } +} + +fn main() { + let _works = TcpListener::bind("some string"); + let bad = NoToSocketAddrs("bad".to_owned()); + let _errors = TcpListener::bind(&bad); + //~^ ERROR the trait bound `NoToSocketAddrs: std::net::ToSocketAddrs` is not satisfied +} diff --git a/src/test/ui/traits/trait-suggest-deferences-issue-39029.stderr b/src/test/ui/traits/trait-suggest-deferences-issue-39029.stderr new file mode 100644 index 000000000000..0bf9794a744c --- /dev/null +++ b/src/test/ui/traits/trait-suggest-deferences-issue-39029.stderr @@ -0,0 +1,19 @@ +error[E0277]: the trait bound `NoToSocketAddrs: std::net::ToSocketAddrs` is not satisfied + --> $DIR/trait-suggest-deferences-issue-39029.rs:16:37 + | +LL | let _errors = TcpListener::bind(&bad); + | ^^^^ + | | + | the trait `std::net::ToSocketAddrs` is not implemented for `NoToSocketAddrs` + | help: consider adding dereference here: `&*bad` + | + ::: $SRC_DIR/libstd/net/tcp.rs:LL:COL + | +LL | pub fn bind(addr: A) -> io::Result { + | ------------- required by this bound in `std::net::TcpListener::bind` + | + = note: required because of the requirements on the impl of `std::net::ToSocketAddrs` for `&NoToSocketAddrs` + +error: aborting due to previous error + +For more information about this error, try `rustc --explain E0277`. diff --git a/src/test/ui/traits/trait-suggest-deferences-issue-62530.fixed b/src/test/ui/traits/trait-suggest-deferences-issue-62530.fixed new file mode 100644 index 000000000000..fa7b9167d8d7 --- /dev/null +++ b/src/test/ui/traits/trait-suggest-deferences-issue-62530.fixed @@ -0,0 +1,15 @@ +// run-rustfix +fn takes_str(_x: &str) {} + +fn takes_type_parameter(_x: T) where T: SomeTrait {} + +trait SomeTrait {} +impl SomeTrait for &'_ str {} +impl SomeTrait for char {} + +fn main() { + let string = String::new(); + takes_str(&string); // Ok + takes_type_parameter(&*string); // Error + //~^ ERROR the trait bound `&std::string::String: SomeTrait` is not satisfied +} diff --git a/src/test/ui/traits/trait-suggest-deferences-issue-62530.rs b/src/test/ui/traits/trait-suggest-deferences-issue-62530.rs new file mode 100644 index 000000000000..e785f0121773 --- /dev/null +++ b/src/test/ui/traits/trait-suggest-deferences-issue-62530.rs @@ -0,0 +1,15 @@ +// run-rustfix +fn takes_str(_x: &str) {} + +fn takes_type_parameter(_x: T) where T: SomeTrait {} + +trait SomeTrait {} +impl SomeTrait for &'_ str {} +impl SomeTrait for char {} + +fn main() { + let string = String::new(); + takes_str(&string); // Ok + takes_type_parameter(&string); // Error + //~^ ERROR the trait bound `&std::string::String: SomeTrait` is not satisfied +} diff --git a/src/test/ui/traits/trait-suggest-deferences-issue-62530.stderr b/src/test/ui/traits/trait-suggest-deferences-issue-62530.stderr new file mode 100644 index 000000000000..9c2a582638ec --- /dev/null +++ b/src/test/ui/traits/trait-suggest-deferences-issue-62530.stderr @@ -0,0 +1,15 @@ +error[E0277]: the trait bound `&std::string::String: SomeTrait` is not satisfied + --> $DIR/trait-suggest-deferences-issue-62530.rs:13:26 + | +LL | fn takes_type_parameter(_x: T) where T: SomeTrait {} + | --------- required by this bound in `takes_type_parameter` +... +LL | takes_type_parameter(&string); // Error + | ^^^^^^^ + | | + | the trait `SomeTrait` is not implemented for `&std::string::String` + | help: consider adding dereference here: `&*string` + +error: aborting due to previous error + +For more information about this error, try `rustc --explain E0277`. diff --git a/src/test/ui/traits/trait-suggest-deferences-multiple.fixed b/src/test/ui/traits/trait-suggest-deferences-multiple.fixed new file mode 100644 index 000000000000..b7160b75c605 --- /dev/null +++ b/src/test/ui/traits/trait-suggest-deferences-multiple.fixed @@ -0,0 +1,36 @@ +// run-rustfix +use std::ops::Deref; + +trait Happy {} +struct LDM; +impl Happy for &LDM {} + +struct Foo(LDM); +struct Bar(Foo); +struct Baz(Bar); +impl Deref for Foo { + type Target = LDM; + fn deref(&self) -> &Self::Target { + &self.0 + } +} +impl Deref for Bar { + type Target = Foo; + fn deref(&self) -> &Self::Target { + &self.0 + } +} +impl Deref for Baz { + type Target = Bar; + fn deref(&self) -> &Self::Target { + &self.0 + } +} + +fn foo(_: T) where T: Happy {} + +fn main() { + let baz = Baz(Bar(Foo(LDM))); + foo(&***baz); + //~^ ERROR the trait bound `&Baz: Happy` is not satisfied +} diff --git a/src/test/ui/traits/trait-suggest-deferences-multiple.rs b/src/test/ui/traits/trait-suggest-deferences-multiple.rs new file mode 100644 index 000000000000..9ac55177ffad --- /dev/null +++ b/src/test/ui/traits/trait-suggest-deferences-multiple.rs @@ -0,0 +1,36 @@ +// run-rustfix +use std::ops::Deref; + +trait Happy {} +struct LDM; +impl Happy for &LDM {} + +struct Foo(LDM); +struct Bar(Foo); +struct Baz(Bar); +impl Deref for Foo { + type Target = LDM; + fn deref(&self) -> &Self::Target { + &self.0 + } +} +impl Deref for Bar { + type Target = Foo; + fn deref(&self) -> &Self::Target { + &self.0 + } +} +impl Deref for Baz { + type Target = Bar; + fn deref(&self) -> &Self::Target { + &self.0 + } +} + +fn foo(_: T) where T: Happy {} + +fn main() { + let baz = Baz(Bar(Foo(LDM))); + foo(&baz); + //~^ ERROR the trait bound `&Baz: Happy` is not satisfied +} diff --git a/src/test/ui/traits/trait-suggest-deferences-multiple.stderr b/src/test/ui/traits/trait-suggest-deferences-multiple.stderr new file mode 100644 index 000000000000..f9b8bba4b412 --- /dev/null +++ b/src/test/ui/traits/trait-suggest-deferences-multiple.stderr @@ -0,0 +1,15 @@ +error[E0277]: the trait bound `&Baz: Happy` is not satisfied + --> $DIR/trait-suggest-deferences-multiple.rs:34:9 + | +LL | fn foo(_: T) where T: Happy {} + | ----- required by this bound in `foo` +... +LL | foo(&baz); + | ^^^^ + | | + | the trait `Happy` is not implemented for `&Baz` + | help: consider adding dereference here: `&***baz` + +error: aborting due to previous error + +For more information about this error, try `rustc --explain E0277`.