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show suggestion to replace generic bounds with associated types in more cases

This commit is contained in:
Robin Appelman 2022-03-27 20:45:08 +02:00
parent 878c7833f6
commit decc04dbfb
6 changed files with 82 additions and 24 deletions
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18
compiler/rustc_typeck/src/astconv/errors.rs
View File

@ -10,7 +10,6 @@ use rustc_span::symbol::{sym, Ident};
use rustc_span::{Span, DUMMY_SP};
use std::collections::BTreeSet;
use std::iter;
impl<'o, 'tcx> dyn AstConv<'tcx> + 'o {
/// On missing type parameters, emit an E0393 error and provide a structured suggestion using
@ -323,6 +322,7 @@ impl<'o, 'tcx> dyn AstConv<'tcx> + 'o {
let mut suggestions = vec![];
let mut types_count = 0;
let mut where_constraints = vec![];
let mut already_has_generics_args_suggestion = false;
for (span, assoc_items) in &associated_types {
let mut names: FxHashMap<_, usize> = FxHashMap::default();
for item in assoc_items {
@ -343,16 +343,10 @@ impl<'o, 'tcx> dyn AstConv<'tcx> + 'o {
}
}
if potential_assoc_types.len() == assoc_items.len() {
// Only suggest when the amount of missing associated types equals the number of
// extra type arguments present, as that gives us a relatively high confidence
// that the user forgot to give the associated type's name. The canonical
// example would be trying to use `Iterator<isize>` instead of
// `Iterator<Item = isize>`.
for (potential, item) in iter::zip(&potential_assoc_types, assoc_items) {
if let Ok(snippet) = tcx.sess.source_map().span_to_snippet(*potential) {
suggestions.push((*potential, format!("{} = {}", item.name, snippet)));
}
}
// When the amount of missing associated types equals the number of
// extra type arguments present. A suggesting to replace the generic args with
// associated types is already emitted.
already_has_generics_args_suggestion = true;
} else if let (Ok(snippet), false) =
(tcx.sess.source_map().span_to_snippet(*span), dupes)
{
@ -382,7 +376,7 @@ impl<'o, 'tcx> dyn AstConv<'tcx> + 'o {
// the same associated type name.
err.help(where_msg);
}
if suggestions.len() != 1 {
if suggestions.len() != 1 || already_has_generics_args_suggestion {
// We don't need this label if there's an inline suggestion, show otherwise.
for (span, assoc_items) in &associated_types {
let mut names: FxHashMap<_, usize> = FxHashMap::default();

45
compiler/rustc_typeck/src/structured_errors/wrong_number_of_generic_args.rs
View File

@ -6,9 +6,10 @@ use rustc_errors::{
use rustc_hir as hir;
use rustc_middle::hir::map::fn_sig;
use rustc_middle::middle::resolve_lifetime::LifetimeScopeForPath;
use rustc_middle::ty::{self as ty, TyCtxt};
use rustc_middle::ty::{self as ty, AssocItems, AssocKind, TyCtxt};
use rustc_session::Session;
use rustc_span::def_id::DefId;
use std::iter;
use GenericArgsInfo::*;
@ -334,6 +335,22 @@ impl<'a, 'tcx> WrongNumberOfGenericArgs<'a, 'tcx> {
.join(", ")
}
fn get_unbound_associated_types(&self) -> Vec<String> {
if self.tcx.is_trait(self.def_id) {
let items: &AssocItems<'_> = self.tcx.associated_items(self.def_id);
items
.in_definition_order()
.filter(|item| item.kind == AssocKind::Type)
.filter(|item| {
!self.gen_args.bindings.iter().any(|binding| binding.ident.name == item.name)
})
.map(|item| item.name.to_ident_string())
.collect()
} else {
Vec::default()
}
}
fn create_error_message(&self) -> String {
let def_path = self.tcx.def_path_str(self.def_id);
let def_kind = self.tcx.def_kind(self.def_id).descr(self.def_id);
@ -618,6 +635,7 @@ impl<'a, 'tcx> WrongNumberOfGenericArgs<'a, 'tcx> {
fn suggest_removing_args_or_generics(&self, err: &mut Diagnostic) {
let num_provided_lt_args = self.num_provided_lifetime_args();
let num_provided_type_const_args = self.num_provided_type_or_const_args();
let unbound_types = self.get_unbound_associated_types();
let num_provided_args = num_provided_lt_args + num_provided_type_const_args;
assert!(num_provided_args > 0);
@ -629,6 +647,8 @@ impl<'a, 'tcx> WrongNumberOfGenericArgs<'a, 'tcx> {
let redundant_type_or_const_args = num_redundant_type_or_const_args > 0;
let remove_entire_generics = num_redundant_args >= self.gen_args.args.len();
let provided_args_matches_unbound_traits =
unbound_types.len() == num_redundant_type_or_const_args;
let remove_lifetime_args = |err: &mut Diagnostic| {
let mut lt_arg_spans = Vec::new();
@ -713,7 +733,28 @@ impl<'a, 'tcx> WrongNumberOfGenericArgs<'a, 'tcx> {
);
};
if remove_entire_generics {
// If there is a single unbound associated type and a single excess generic param
// suggest replacing the generic param with the associated type bound
if provided_args_matches_unbound_traits && !unbound_types.is_empty() {
let mut suggestions = vec![];
let unused_generics = &self.gen_args.args[self.num_expected_type_or_const_args()..];
for (potential, name) in iter::zip(unused_generics, &unbound_types) {
if let Ok(snippet) = self.tcx.sess.source_map().span_to_snippet(potential.span()) {
suggestions.push((potential.span(), format!("{} = {}", name, snippet)));
}
}
if !suggestions.is_empty() {
err.multipart_suggestion(
&format!(
"replace the generic bound{s} with the associated type{s}",
s = pluralize!(unbound_types.len())
),
suggestions,
Applicability::MaybeIncorrect,
);
}
} else if remove_entire_generics {
let span = self
.path_segment
.args

2
src/test/ui/const-generics/issues/issue-87493.stderr
View File

@ -13,7 +13,7 @@ error[E0107]: this trait takes 0 generic arguments but 1 generic argument was su
--> $DIR/issue-87493.rs:8:8
|
LL | T: MyTrait<Assoc == S::Assoc>,
| ^^^^^^^------------------- help: remove these generics
| ^^^^^^^ ----------------- help: replace the generic bound with the associated type: `Assoc = Assoc == S::Assoc`
| |
| expected 0 generic arguments
|

10
src/test/ui/error-codes/E0107.rs
View File

@ -47,4 +47,14 @@ struct Baz<'a, 'b, 'c> {
//~| HELP remove this lifetime argument
}
pub trait T {
type A;
type B;
}
fn trait_bound_generic<I: T<u8, u16>>(_i: I) {
//~^ ERROR this trait takes 0 generic arguments
//~| HELP replace the generic bounds with the associated types
}
fn main() {}

18
src/test/ui/error-codes/E0107.stderr
View File

@ -128,6 +128,22 @@ note: struct defined here, with 0 lifetime parameters
LL | struct Quux<T>(T);
| ^^^^
error: aborting due to 9 previous errors
error[E0107]: this trait takes 0 generic arguments but 2 generic arguments were supplied
--> $DIR/E0107.rs:55:27
|
LL | fn trait_bound_generic<I: T<u8, u16>>(_i: I) {
| ^ expected 0 generic arguments
|
note: trait defined here, with 0 generic parameters
--> $DIR/E0107.rs:50:11
|
LL | pub trait T {
| ^
help: replace the generic bounds with the associated types
|
LL | fn trait_bound_generic<I: T<A = u8, B = u16>>(_i: I) {
| ~~~~~~ ~~~~~~~
error: aborting due to 10 previous errors
For more information about this error, try `rustc --explain E0107`.

13
src/test/ui/suggestions/use-type-argument-instead-of-assoc-type.stderr
View File

@ -2,15 +2,17 @@ error[E0107]: this trait takes 2 generic arguments but 4 generic arguments were
--> $DIR/use-type-argument-instead-of-assoc-type.rs:7:16
|
LL | i: Box<dyn T<usize, usize, usize, usize, B=usize>>,
| ^ ------------ help: remove these generic arguments
| |
| expected 2 generic arguments
| ^ expected 2 generic arguments
|
note: trait defined here, with 2 generic parameters: `X`, `Y`
--> $DIR/use-type-argument-instead-of-assoc-type.rs:1:11
|
LL | pub trait T<X, Y> {
| ^ - -
help: replace the generic bounds with the associated types
|
LL | i: Box<dyn T<usize, usize, A = usize, C = usize, B=usize>>,
| ~~~~~~~~~ ~~~~~~~~~
error[E0191]: the value of the associated types `A` (from trait `T`), `C` (from trait `T`) must be specified
--> $DIR/use-type-argument-instead-of-assoc-type.rs:7:16
@ -23,11 +25,6 @@ LL | type C;
...
LL | i: Box<dyn T<usize, usize, usize, usize, B=usize>>,
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ associated types `A`, `C` must be specified
|
help: specify the associated types
|
LL | i: Box<dyn T<usize, usize, A = usize, C = usize, B=usize>>,
| ~~~~~~~~~ ~~~~~~~~~
error: aborting due to 2 previous errors