Optimized error reporting for recursive requirements #47720
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@ -1194,13 +1194,15 @@ impl<'a, 'gcx, 'tcx> InferCtxt<'a, 'gcx, 'tcx> {
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{
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self.note_obligation_cause_code(err,
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&obligation.predicate,
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&obligation.cause.code);
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&obligation.cause.code,
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&mut vec![]);
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}
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fn note_obligation_cause_code<T>(&self,
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err: &mut DiagnosticBuilder,
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predicate: &T,
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cause_code: &ObligationCauseCode<'tcx>)
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cause_code: &ObligationCauseCode<'tcx>,
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obligated_types: &mut Vec<&ty::TyS<'tcx>>)
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where T: fmt::Display
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{
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let tcx = self.tcx;
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@ -1292,12 +1294,17 @@ impl<'a, 'gcx, 'tcx> InferCtxt<'a, 'gcx, 'tcx> {
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}
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ObligationCauseCode::BuiltinDerivedObligation(ref data) => {
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let parent_trait_ref = self.resolve_type_vars_if_possible(&data.parent_trait_ref);
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err.note(&format!("required because it appears within the type `{}`",
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parent_trait_ref.0.self_ty()));
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let ty = parent_trait_ref.0.self_ty();
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err.note(&format!("required because it appears within the type `{}`", ty));
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obligated_types.push(ty);
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let parent_predicate = parent_trait_ref.to_predicate();
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self.note_obligation_cause_code(err,
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&parent_predicate,
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&data.parent_code);
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if !self.is_recursive_obligation(obligated_types, &data.parent_code) {
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self.note_obligation_cause_code(err,
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&parent_predicate,
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&data.parent_code,
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obligated_types);
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}
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}
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ObligationCauseCode::ImplDerivedObligation(ref data) => {
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let parent_trait_ref = self.resolve_type_vars_if_possible(&data.parent_trait_ref);
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@ -1307,8 +1314,9 @@ impl<'a, 'gcx, 'tcx> InferCtxt<'a, 'gcx, 'tcx> {
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parent_trait_ref.0.self_ty()));
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let parent_predicate = parent_trait_ref.to_predicate();
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self.note_obligation_cause_code(err,
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&parent_predicate,
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&data.parent_code);
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&parent_predicate,
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&data.parent_code,
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obligated_types);
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}
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ObligationCauseCode::CompareImplMethodObligation { .. } => {
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err.note(
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@ -1327,6 +1335,20 @@ impl<'a, 'gcx, 'tcx> InferCtxt<'a, 'gcx, 'tcx> {
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err.help(&format!("consider adding a `#![recursion_limit=\"{}\"]` attribute to your crate",
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suggested_limit));
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}
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fn is_recursive_obligation(&self,
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obligated_types: &mut Vec<&ty::TyS<'tcx>>,
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cause_code: &ObligationCauseCode<'tcx>) -> bool {
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if let ObligationCauseCode::BuiltinDerivedObligation(ref data) = cause_code {
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let parent_trait_ref = self.resolve_type_vars_if_possible(&data.parent_trait_ref);
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for obligated_type in obligated_types {
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if obligated_type == &parent_trait_ref.0.self_ty() {
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return true;
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}
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}
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}
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return false;
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}
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}
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enum ArgKind {
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@ -0,0 +1,27 @@
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// Copyright 2018 The Rust Project Developers. See the COPYRIGHT
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// file at the top-level directory of this distribution and at
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// http://rust-lang.org/COPYRIGHT.
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//
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// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
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// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
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// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
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// option. This file may not be copied, modified, or distributed
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// except according to those terms.
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use std::marker::PhantomData;
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struct AssertSync<T: Sync>(PhantomData<T>);
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pub struct Foo {
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bar: *const Bar,
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phantom: PhantomData<Bar>,
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}
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pub struct Bar {
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foo: *const Foo,
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phantom: PhantomData<Foo>,
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}
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fn main() {
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let _: AssertSync<Foo> = unimplemented!(); //~ ERROR E0275
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}
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@ -0,0 +1,14 @@
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error[E0275]: overflow evaluating the requirement `Foo: std::marker::Sync`
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--> $DIR/recursive-requirements.rs:26:12
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26 | let _: AssertSync<Foo> = unimplemented!(); //~ ERROR E0275
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| ^^^^^^^^^^^^^^^
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= help: consider adding a `#![recursion_limit="128"]` attribute to your crate
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= note: required because it appears within the type `std::marker::PhantomData<Foo>`
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= note: required because it appears within the type `Bar`
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= note: required because it appears within the type `std::marker::PhantomData<Bar>`
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= note: required because it appears within the type `Foo`
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error: aborting due to previous error
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