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estebank committed Nov 24, 2019
1 parent 9fb446d commit 0f530ecb6875540f5cf5032ea7df54a38d01ab1c
@@ -16,9 +16,9 @@ use crate::ty::AdtKind;
use crate::ty::query::Providers;
use crate::util::nodemap::{NodeMap, FxHashSet};

use errors::{Applicability, DiagnosticBuilder, FatalError};
use errors::FatalError;
use syntax_pos::{Span, DUMMY_SP, MultiSpan};
use syntax::source_map::{Spanned, SourceMap};
use syntax::source_map::Spanned;
use syntax::ast::{self, CrateSugar, Ident, Name, NodeId, AsmDialect};
use syntax::ast::{Attribute, Label, LitKind, StrStyle, FloatTy, IntTy, UintTy};
pub use syntax::ast::{Mutability, Constness, Unsafety, Movability, CaptureBy};
@@ -644,79 +644,6 @@ impl Generics {
self.params.iter().map(|p| p.span).collect::<Vec<Span>>().into()
}
}

/// Suggest restricting a type param with a new bound.
pub fn suggest_constraining_type_param(
&self,
err: &mut DiagnosticBuilder<'_>,
param_name: &str,
constraint: &str,
source_map: &SourceMap,
span: Span,
) -> bool {
let restrict_msg = "consider further restricting this bound";
if let Some(param) = self.params.iter().filter(|p| {
p.name.ident().as_str() == param_name
}).next() {
if param_name.starts_with("impl ") {
// `impl Trait` in argument:
// `fn foo(x: impl Trait) {}` → `fn foo(t: impl Trait + Trait2) {}`
err.span_suggestion(
param.span,
restrict_msg,
// `impl CurrentTrait + MissingTrait`
format!("{} + {}", param_name, constraint),
Applicability::MachineApplicable,
);
} else if self.where_clause.predicates.is_empty() &&
param.bounds.is_empty()
{
// If there are no bounds whatsoever, suggest adding a constraint
// to the type parameter:
// `fn foo<T>(t: T) {}` → `fn foo<T: Trait>(t: T) {}`
err.span_suggestion(
param.span,
"consider restricting this bound",
format!("{}: {}", param_name, constraint),
Applicability::MachineApplicable,
);
} else if !self.where_clause.predicates.is_empty() {
// There is a `where` clause, so suggest expanding it:
// `fn foo<T>(t: T) where T: Debug {}` →
// `fn foo<T>(t: T) where T: Debug, T: Trait {}`
err.span_suggestion(
self.where_clause.span().unwrap().shrink_to_hi(),
&format!("consider further restricting type parameter `{}`", param_name),
format!(", {}: {}", param_name, constraint),
Applicability::MachineApplicable,
);
} else {
// If there is no `where` clause lean towards constraining to the
// type parameter:
// `fn foo<X: Bar, T>(t: T, x: X) {}` → `fn foo<T: Trait>(t: T) {}`
// `fn foo<T: Bar>(t: T) {}` → `fn foo<T: Bar + Trait>(t: T) {}`
let sp = param.span.with_hi(span.hi());
let span = source_map.span_through_char(sp, ':');
if sp != param.span && sp != span {
// Only suggest if we have high certainty that the span
// covers the colon in `foo<T: Trait>`.
err.span_suggestion(
span,
restrict_msg,
format!("{}: {} + ", param_name, constraint),
Applicability::MachineApplicable,
);
} else {
err.span_label(
param.span,
&format!("consider adding a `where {}: {}` bound", param_name, constraint),
);
}
}
return true;
}
false
}
}

/// Synthetic type parameters are converted to another form during lowering; this allows
@@ -39,6 +39,7 @@ use syntax::ast;
use syntax::symbol::{sym, kw};
use syntax_pos::{DUMMY_SP, Span, ExpnKind, MultiSpan};
use rustc::hir::def_id::LOCAL_CRATE;
use syntax_pos::source_map::SourceMap;

use rustc_error_codes::*;

@@ -1189,7 +1190,8 @@ impl<'a, 'tcx> InferCtxt<'a, 'tcx> {
// Missing generic type parameter bound.
let param_name = self_ty.to_string();
let constraint = trait_ref.to_string();
if generics.suggest_constraining_type_param(
if suggest_constraining_type_param(
generics,
&mut err,
&param_name,
&constraint,
@@ -2497,3 +2499,76 @@ impl ArgKind {
}
}
}

/// Suggest restricting a type param with a new bound.
pub fn suggest_constraining_type_param(
generics: &hir::Generics,
err: &mut DiagnosticBuilder<'_>,
param_name: &str,
constraint: &str,
source_map: &SourceMap,
span: Span,
) -> bool {
let restrict_msg = "consider further restricting this bound";
if let Some(param) = generics.params.iter().filter(|p| {
p.name.ident().as_str() == param_name
}).next() {
if param_name.starts_with("impl ") {
// `impl Trait` in argument:
// `fn foo(x: impl Trait) {}` → `fn foo(t: impl Trait + Trait2) {}`
err.span_suggestion(
param.span,
restrict_msg,
// `impl CurrentTrait + MissingTrait`
format!("{} + {}", param_name, constraint),
Applicability::MachineApplicable,
);
} else if generics.where_clause.predicates.is_empty() &&
param.bounds.is_empty()
{
// If there are no bounds whatsoever, suggest adding a constraint
// to the type parameter:
// `fn foo<T>(t: T) {}` → `fn foo<T: Trait>(t: T) {}`
err.span_suggestion(
param.span,
"consider restricting this bound",
format!("{}: {}", param_name, constraint),
Applicability::MachineApplicable,
);
} else if !generics.where_clause.predicates.is_empty() {
// There is a `where` clause, so suggest expanding it:
// `fn foo<T>(t: T) where T: Debug {}` →
// `fn foo<T>(t: T) where T: Debug, T: Trait {}`
err.span_suggestion(
generics.where_clause.span().unwrap().shrink_to_hi(),
&format!("consider further restricting type parameter `{}`", param_name),
format!(", {}: {}", param_name, constraint),
Applicability::MachineApplicable,
);
} else {
// If there is no `where` clause lean towards constraining to the
// type parameter:
// `fn foo<X: Bar, T>(t: T, x: X) {}` → `fn foo<T: Trait>(t: T) {}`
// `fn foo<T: Bar>(t: T) {}` → `fn foo<T: Bar + Trait>(t: T) {}`
let sp = param.span.with_hi(span.hi());
let span = source_map.span_through_char(sp, ':');
if sp != param.span && sp != span {
// Only suggest if we have high certainty that the span
// covers the colon in `foo<T: Trait>`.
err.span_suggestion(
span,
restrict_msg,
format!("{}: {} + ", param_name, constraint),
Applicability::MachineApplicable,
);
} else {
err.span_label(
param.span,
&format!("consider adding a `where {}: {}` bound", param_name, constraint),
);
}
}
return true;
}
false
}
@@ -7,6 +7,7 @@ use rustc::mir::{
PlaceRef, ProjectionElem, Rvalue, Statement, StatementKind, TerminatorKind, VarBindingForm,
};
use rustc::ty::{self, Ty};
use rustc::traits::error_reporting::suggest_constraining_type_param;
use rustc_data_structures::fx::FxHashSet;
use rustc_index::vec::Idx;
use rustc_errors::{Applicability, DiagnosticBuilder};
@@ -233,7 +234,8 @@ impl<'cx, 'tcx> MirBorrowckCtxt<'cx, 'tcx> {
let generics = tcx.generics_of(self.mir_def_id);
let param = generics.type_param(&param_ty, tcx);
let generics = tcx.hir().get_generics(self.mir_def_id).unwrap();
generics.suggest_constraining_type_param(
suggest_constraining_type_param(
generics,
&mut err,
&param.name.as_str(),
"Copy",

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