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Auto merge of #87033 - FabianWolff:issue-87017, r=estebank

Provide a suggestion when trying to destructure a `Vec` as a slice

Fixes #87017.

r? `@estebank`
This commit is contained in:
bors 2021-08-03 08:00:30 +00:00
commit 3354a44d2f
5 changed files with 110 additions and 2 deletions

View file

@ -16,6 +16,7 @@ use rustc_span::lev_distance::find_best_match_for_name;
use rustc_span::source_map::{Span, Spanned}; use rustc_span::source_map::{Span, Spanned};
use rustc_span::symbol::Ident; use rustc_span::symbol::Ident;
use rustc_span::{BytePos, DUMMY_SP}; use rustc_span::{BytePos, DUMMY_SP};
use rustc_trait_selection::autoderef::Autoderef;
use rustc_trait_selection::traits::{ObligationCause, Pattern}; use rustc_trait_selection::traits::{ObligationCause, Pattern};
use ty::VariantDef; use ty::VariantDef;
@ -1769,7 +1770,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
// The expected type must be an array or slice, but was neither, so error. // The expected type must be an array or slice, but was neither, so error.
_ => { _ => {
if !expected.references_error() { if !expected.references_error() {
self.error_expected_array_or_slice(span, expected); self.error_expected_array_or_slice(span, expected, ti);
} }
let err = self.tcx.ty_error(); let err = self.tcx.ty_error();
(err, Some(err), err) (err, Some(err), err)
@ -1882,7 +1883,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
.emit(); .emit();
} }
fn error_expected_array_or_slice(&self, span: Span, expected_ty: Ty<'tcx>) { fn error_expected_array_or_slice(&self, span: Span, expected_ty: Ty<'tcx>, ti: TopInfo<'tcx>) {
let mut err = struct_span_err!( let mut err = struct_span_err!(
self.tcx.sess, self.tcx.sess,
span, span,
@ -1894,6 +1895,19 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
if let ty::Array(..) | ty::Slice(..) = ty.kind() { if let ty::Array(..) | ty::Slice(..) = ty.kind() {
err.help("the semantics of slice patterns changed recently; see issue #62254"); err.help("the semantics of slice patterns changed recently; see issue #62254");
} }
} else if Autoderef::new(&self.infcx, self.param_env, self.body_id, span, expected_ty, span)
.any(|(ty, _)| matches!(ty.kind(), ty::Slice(..)))
{
if let (Some(span), true) = (ti.span, ti.origin_expr) {
if let Ok(snippet) = self.tcx.sess.source_map().span_to_snippet(span) {
err.span_suggestion(
span,
"consider slicing here",
format!("{}[..]", snippet),
Applicability::MachineApplicable,
);
}
}
} }
err.span_label(span, format!("pattern cannot match with input type `{}`", expected_ty)); err.span_label(span, format!("pattern cannot match with input type `{}`", expected_ty));
err.emit(); err.emit();

View file

@ -15,12 +15,16 @@ LL | [&v] => {},
error[E0529]: expected an array or slice, found `Vec<i32>` error[E0529]: expected an array or slice, found `Vec<i32>`
--> $DIR/match-ergonomics.rs:8:9 --> $DIR/match-ergonomics.rs:8:9
| |
LL | match x {
| - help: consider slicing here: `x[..]`
LL | [&v] => {}, LL | [&v] => {},
| ^^^^ pattern cannot match with input type `Vec<i32>` | ^^^^ pattern cannot match with input type `Vec<i32>`
error[E0529]: expected an array or slice, found `Vec<i32>` error[E0529]: expected an array or slice, found `Vec<i32>`
--> $DIR/match-ergonomics.rs:20:9 --> $DIR/match-ergonomics.rs:20:9
| |
LL | match x {
| - help: consider slicing here: `x[..]`
LL | [v] => {}, LL | [v] => {},
| ^^^ pattern cannot match with input type `Vec<i32>` | ^^^ pattern cannot match with input type `Vec<i32>`

View file

@ -0,0 +1,27 @@
// Regression test for #87017.
// run-rustfix
fn main() {
fn foo() -> Vec<i32> { vec![1, 2, 3] }
if let [_, _, _] = foo()[..] {}
//~^ ERROR: expected an array or slice
//~| HELP: consider slicing here
if let [] = &foo()[..] {}
//~^ ERROR: expected an array or slice
//~| HELP: consider slicing here
if let [] = foo()[..] {}
//~^ ERROR: expected an array or slice
//~| HELP: consider slicing here
let v = vec![];
match &v[..] {
//~^ HELP: consider slicing here
[5] => {}
//~^ ERROR: expected an array or slice
_ => {}
}
}

View file

@ -0,0 +1,27 @@
// Regression test for #87017.
// run-rustfix
fn main() {
fn foo() -> Vec<i32> { vec![1, 2, 3] }
if let [_, _, _] = foo() {}
//~^ ERROR: expected an array or slice
//~| HELP: consider slicing here
if let [] = &foo() {}
//~^ ERROR: expected an array or slice
//~| HELP: consider slicing here
if let [] = foo() {}
//~^ ERROR: expected an array or slice
//~| HELP: consider slicing here
let v = vec![];
match &v {
//~^ HELP: consider slicing here
[5] => {}
//~^ ERROR: expected an array or slice
_ => {}
}
}

View file

@ -0,0 +1,36 @@
error[E0529]: expected an array or slice, found `Vec<i32>`
--> $DIR/pattern-slice-vec.rs:8:12
|
LL | if let [_, _, _] = foo() {}
| ^^^^^^^^^ ----- help: consider slicing here: `foo()[..]`
| |
| pattern cannot match with input type `Vec<i32>`
error[E0529]: expected an array or slice, found `Vec<i32>`
--> $DIR/pattern-slice-vec.rs:12:12
|
LL | if let [] = &foo() {}
| ^^ ------ help: consider slicing here: `&foo()[..]`
| |
| pattern cannot match with input type `Vec<i32>`
error[E0529]: expected an array or slice, found `Vec<i32>`
--> $DIR/pattern-slice-vec.rs:16:12
|
LL | if let [] = foo() {}
| ^^ ----- help: consider slicing here: `foo()[..]`
| |
| pattern cannot match with input type `Vec<i32>`
error[E0529]: expected an array or slice, found `Vec<_>`
--> $DIR/pattern-slice-vec.rs:23:9
|
LL | match &v {
| -- help: consider slicing here: `&v[..]`
LL |
LL | [5] => {}
| ^^^ pattern cannot match with input type `Vec<_>`
error: aborting due to 4 previous errors
For more information about this error, try `rustc --explain E0529`.