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Check bindings around never patterns

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This commit is contained in:
Nadrieril 2024-01-05 10:11:18 +01:00
parent b31735a401
commit 560beb1ad4
13 changed files with 110 additions and 105 deletions
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4
compiler/rustc_resolve/messages.ftl
View File

@ -36,6 +36,10 @@ resolve_attempt_to_use_non_constant_value_in_constant_with_suggestion =
resolve_attempt_to_use_non_constant_value_in_constant_without_suggestion =
this would need to be a `{$suggestion}`
resolve_binding_in_never_pattern =
never patterns cannot contain variable bindings
.suggestion = use a wildcard `_` instead
resolve_binding_shadows_something_unacceptable =
{$shadowing_binding}s cannot shadow {$shadowed_binding}s
.label = cannot be named the same as {$article} {$shadowed_binding}

3
compiler/rustc_resolve/src/diagnostics.rs
View File

@ -960,6 +960,9 @@ pub(crate) fn into_struct_error(
.create_err(errs::TraitImplDuplicate { span, name, trait_item_span, old_span }),
ResolutionError::InvalidAsmSym => self.dcx().create_err(errs::InvalidAsmSym { span }),
ResolutionError::LowercaseSelf => self.dcx().create_err(errs::LowercaseSelf { span }),
ResolutionError::BindingInNeverPattern => {
self.dcx().create_err(errs::BindingInNeverPattern { span })
}
}
}

9
compiler/rustc_resolve/src/errors.rs
View File

@ -486,6 +486,15 @@ pub(crate) struct LowercaseSelf {
pub(crate) span: Span,
}
#[derive(Debug)]
#[derive(Diagnostic)]
#[diag(resolve_binding_in_never_pattern)]
pub(crate) struct BindingInNeverPattern {
#[primary_span]
#[suggestion(code = "_", applicability = "machine-applicable", style = "short")]
pub(crate) span: Span,
}
#[derive(Diagnostic)]
#[diag(resolve_trait_impl_duplicate, code = "E0201")]
pub(crate) struct TraitImplDuplicate {

59
compiler/rustc_resolve/src/late.rs
View File

@ -65,6 +65,8 @@ enum IsRepeatExpr {
Yes,
}
struct IsNeverPattern;
/// Describes whether an `AnonConst` is a type level const arg or
/// some other form of anon const (i.e. inline consts or enum discriminants)
#[derive(Copy, Clone, Debug, PartialEq, Eq)]
@ -3191,11 +3193,15 @@ fn resolve_local(&mut self, local: &'ast Local) {
}
/// Build a map from pattern identifiers to binding-info's, and check the bindings are
/// consistent when encountering or-patterns.
/// consistent when encountering or-patterns and never patterns.
/// This is done hygienically: this could arise for a macro that expands into an or-pattern
/// where one 'x' was from the user and one 'x' came from the macro.
fn compute_and_check_binding_map(&mut self, pat: &Pat) -> FxIndexMap<Ident, BindingInfo> {
fn compute_and_check_binding_map(
&mut self,
pat: &Pat,
) -> Result<FxIndexMap<Ident, BindingInfo>, IsNeverPattern> {
let mut binding_map = FxIndexMap::default();
let mut is_never_pat = false;
pat.walk(&mut |pat| {
match pat.kind {
@ -3207,17 +3213,26 @@ fn compute_and_check_binding_map(&mut self, pat: &Pat) -> FxIndexMap<Ident, Bind
PatKind::Or(ref ps) => {
// Check the consistency of this or-pattern and
// then add all bindings to the larger map.
let bm = self.compute_and_check_or_pat_binding_map(ps);
let (bm, np) = self.compute_and_check_or_pat_binding_map(ps);
binding_map.extend(bm);
is_never_pat |= np;
return false;
}
PatKind::Never => is_never_pat = true,
_ => {}
}
true
});
binding_map
if is_never_pat {
for (_, binding) in binding_map {
self.report_error(binding.span, ResolutionError::BindingInNeverPattern);
}
Err(IsNeverPattern)
} else {
Ok(binding_map)
}
}
fn is_base_res_local(&self, nid: NodeId) -> bool {
@ -3229,24 +3244,29 @@ fn is_base_res_local(&self, nid: NodeId) -> bool {
/// Compute the binding map for an or-pattern. Checks that all of the arms in the or-pattern
/// have exactly the same set of bindings, with the same binding modes for each.
/// Returns the computed binding map.
/// Returns the computed binding map and a boolean indicating whether the pattern is a never
/// pattern.
fn compute_and_check_or_pat_binding_map(
&mut self,
pats: &[P<Pat>],
) -> FxIndexMap<Ident, BindingInfo> {
) -> (FxIndexMap<Ident, BindingInfo>, bool) {
let mut missing_vars = FxIndexMap::default();
let mut inconsistent_vars = FxIndexMap::default();
// 1) Compute the binding maps of all arms.
let maps =
pats.iter().map(|pat| self.compute_and_check_binding_map(pat)).collect::<Vec<_>>();
// 1) Compute the binding maps of all arms; never patterns don't participate in this.
let not_never_pats = pats
.iter()
.filter_map(|pat| {
let binding_map = self.compute_and_check_binding_map(pat).ok()?;
Some((binding_map, pat))
})
.collect::<Vec<_>>();
// 2) Record any missing bindings or binding mode inconsistencies.
for (map_outer, pat_outer) in maps.iter().zip(pats.iter()) {
for (map_outer, pat_outer) in not_never_pats.iter() {
// Check against all arms except for the same pattern which is always self-consistent.
let inners = maps
let inners = not_never_pats
.iter()
.zip(pats.iter())
.filter(|(_, pat)| pat.id != pat_outer.id)
.flat_map(|(map, _)| map);
@ -3294,22 +3314,17 @@ fn compute_and_check_or_pat_binding_map(
}
// 5) Bubble up the final binding map.
let is_never_pat = not_never_pats.is_empty();
let mut binding_map = FxIndexMap::default();
for bm in maps {
for (bm, _) in not_never_pats {
binding_map.extend(bm);
}
binding_map
(binding_map, is_never_pat)
}
/// Check the consistency of bindings wrt or-patterns.
/// Check the consistency of bindings wrt or-patterns and never patterns.
fn check_consistent_bindings(&mut self, pat: &'ast Pat) {
pat.walk(&mut |pat| match pat.kind {
PatKind::Or(ref ps) => {
let _ = self.compute_and_check_or_pat_binding_map(ps);
false
}
_ => true,
})
let _ = self.compute_and_check_binding_map(pat);
}
fn resolve_arm(&mut self, arm: &'ast Arm) {

2
compiler/rustc_resolve/src/lib.rs
View File

@ -265,6 +265,8 @@ enum ResolutionError<'a> {
InvalidAsmSym,
/// `self` used instead of `Self` in a generic parameter
LowercaseSelf,
/// A never pattern has a binding.
BindingInNeverPattern,
}
enum VisResolutionError<'a> {

1
tests/ui/feature-gates/feature-gate-never_patterns.rs
View File

@ -7,7 +7,6 @@ fn main() {
let res: Result<u32, Void> = Ok(0);
let (Ok(_x) | Err(&!)) = res.as_ref();
//~^ ERROR `!` patterns are experimental
//~| ERROR: is not bound in all patterns
unsafe {
let ptr: *const Void = NonNull::dangling().as_ptr();

37
tests/ui/feature-gates/feature-gate-never_patterns.stderr
View File

@ -1,5 +1,5 @@
error: unexpected `,` in pattern
--> $DIR/feature-gate-never_patterns.rs:34:16
--> $DIR/feature-gate-never_patterns.rs:33:16
|
LL | Some(_),
| ^
@ -13,14 +13,6 @@ help: ...or a vertical bar to match on multiple alternatives
LL | Some(_) |
|
error[E0408]: variable `_x` is not bound in all patterns
--> $DIR/feature-gate-never_patterns.rs:8:19
|
LL | let (Ok(_x) | Err(&!)) = res.as_ref();
| -- ^^^^^^^ pattern doesn't bind `_x`
| |
| variable not in all patterns
error[E0658]: `!` patterns are experimental
--> $DIR/feature-gate-never_patterns.rs:8:24
|
@ -31,7 +23,7 @@ LL | let (Ok(_x) | Err(&!)) = res.as_ref();
= help: add `#![feature(never_patterns)]` to the crate attributes to enable
error[E0658]: `!` patterns are experimental
--> $DIR/feature-gate-never_patterns.rs:15:13
--> $DIR/feature-gate-never_patterns.rs:14:13
|
LL | !
| ^
@ -40,7 +32,7 @@ LL | !
= help: add `#![feature(never_patterns)]` to the crate attributes to enable
error[E0658]: `!` patterns are experimental
--> $DIR/feature-gate-never_patterns.rs:21:13
--> $DIR/feature-gate-never_patterns.rs:20:13
|
LL | !
| ^
@ -49,7 +41,7 @@ LL | !
= help: add `#![feature(never_patterns)]` to the crate attributes to enable
error[E0658]: `!` patterns are experimental
--> $DIR/feature-gate-never_patterns.rs:26:13
--> $DIR/feature-gate-never_patterns.rs:25:13
|
LL | ! => {}
| ^
@ -58,25 +50,25 @@ LL | ! => {}
= help: add `#![feature(never_patterns)]` to the crate attributes to enable
error: `match` arm with no body
--> $DIR/feature-gate-never_patterns.rs:39:9
--> $DIR/feature-gate-never_patterns.rs:38:9
|
LL | Some(_)
| ^^^^^^^- help: add a body after the pattern: `=> todo!(),`
error: `match` arm with no body
--> $DIR/feature-gate-never_patterns.rs:44:9
--> $DIR/feature-gate-never_patterns.rs:43:9
|
LL | Some(_) if false,
| ^^^^^^^- help: add a body after the pattern: `=> todo!(),`
error: `match` arm with no body
--> $DIR/feature-gate-never_patterns.rs:46:9
--> $DIR/feature-gate-never_patterns.rs:45:9
|
LL | Some(_) if false
| ^^^^^^^- help: add a body after the pattern: `=> todo!(),`
error[E0658]: `!` patterns are experimental
--> $DIR/feature-gate-never_patterns.rs:51:13
--> $DIR/feature-gate-never_patterns.rs:50:13
|
LL | Err(!),
| ^
@ -85,7 +77,7 @@ LL | Err(!),
= help: add `#![feature(never_patterns)]` to the crate attributes to enable
error[E0658]: `!` patterns are experimental
--> $DIR/feature-gate-never_patterns.rs:55:13
--> $DIR/feature-gate-never_patterns.rs:54:13
|
LL | Err(!) if false,
| ^
@ -94,24 +86,23 @@ LL | Err(!) if false,
= help: add `#![feature(never_patterns)]` to the crate attributes to enable
error: `match` arm with no body
--> $DIR/feature-gate-never_patterns.rs:65:9
--> $DIR/feature-gate-never_patterns.rs:64:9
|
LL | Some(_)
| ^^^^^^^- help: add a body after the pattern: `=> todo!(),`
error: `match` arm with no body
--> $DIR/feature-gate-never_patterns.rs:71:9
--> $DIR/feature-gate-never_patterns.rs:70:9
|
LL | Some(_) if false
| ^^^^^^^- help: add a body after the pattern: `=> todo!(),`
error: a guard on a never pattern will never be run
--> $DIR/feature-gate-never_patterns.rs:55:19
--> $DIR/feature-gate-never_patterns.rs:54:19
|
LL | Err(!) if false,
| ^^^^^ help: remove this guard
error: aborting due to 14 previous errors
error: aborting due to 13 previous errors
Some errors have detailed explanations: E0408, E0658.
For more information about an error, try `rustc --explain E0408`.
For more information about this error, try `rustc --explain E0658`.

5
tests/ui/pattern/never_patterns.rs
View File

@ -7,12 +7,9 @@ fn main() {}
// The classic use for empty types.
fn safe_unwrap_result<T>(res: Result<T, Void>) {
let Ok(_x) = res;
// FIXME(never_patterns): These should be allowed
let Ok(_x) = res; //~ ERROR refutable pattern in local binding
let (Ok(_x) | Err(!)) = &res;
//~^ ERROR: is not bound in all patterns
let (Ok(_x) | Err(&!)) = res.as_ref();
//~^ ERROR: is not bound in all patterns
}
// Check we only accept `!` where we want to.

28
tests/ui/pattern/never_patterns.stderr
View File

@ -1,19 +1,17 @@
error[E0408]: variable `_x` is not bound in all patterns
--> $DIR/never_patterns.rs:12:19
error[E0005]: refutable pattern in local binding
--> $DIR/never_patterns.rs:10:9
|
LL | let (Ok(_x) | Err(!)) = &res;
| -- ^^^^^^ pattern doesn't bind `_x`
| |
| variable not in all patterns
error[E0408]: variable `_x` is not bound in all patterns
--> $DIR/never_patterns.rs:14:19
LL | let Ok(_x) = res;
| ^^^^^^ pattern `Err(_)` not covered
|
LL | let (Ok(_x) | Err(&!)) = res.as_ref();
| -- ^^^^^^^ pattern doesn't bind `_x`
| |
| variable not in all patterns
= note: `let` bindings require an "irrefutable pattern", like a `struct` or an `enum` with only one variant
= note: for more information, visit https://doc.rust-lang.org/book/ch18-02-refutability.html
= note: the matched value is of type `Result<T, Void>`
help: you might want to use `let else` to handle the variant that isn't matched
|
LL | let Ok(_x) = res else { todo!() };
| ++++++++++++++++
error: aborting due to 2 previous errors
error: aborting due to 1 previous error
For more information about this error, try `rustc --explain E0408`.
For more information about this error, try `rustc --explain E0005`.

11
tests/ui/rfcs/rfc-0000-never_patterns/bindings.rs
View File

@ -6,23 +6,20 @@ enum Void {}
fn main() {
let x: Result<bool, &(u32, u32, Void)> = Ok(false);
// FIXME(never_patterns): Never patterns in or-patterns don't need to share the same bindings.
match x {
Ok(_x) | Err(&!) => {}
//~^ ERROR: is not bound in all patterns
}
let (Ok(_x) | Err(&!)) = x;
//~^ ERROR: is not bound in all patterns
// FIXME(never_patterns): A never pattern mustn't have bindings.
match x {
Ok(_) => {}
Err(&(_a, _b, !)),
//~^ ERROR: never patterns cannot contain variable bindings
//~| ERROR: never patterns cannot contain variable bindings
}
match x {
Ok(_ok) | Err(&(_a, _b, !)) => {}
//~^ ERROR: is not bound in all patterns
//~| ERROR: is not bound in all patterns
//~| ERROR: is not bound in all patterns
//~^ ERROR: never patterns cannot contain variable bindings
//~| ERROR: never patterns cannot contain variable bindings
}
}

47
tests/ui/rfcs/rfc-0000-never_patterns/bindings.stderr
View File

@ -1,43 +1,26 @@
error[E0408]: variable `_x` is not bound in all patterns
--> $DIR/bindings.rs:11:18
error: never patterns cannot contain variable bindings
--> $DIR/bindings.rs:16:15
|
LL | Ok(_x) | Err(&!) => {}
| -- ^^^^^^^ pattern doesn't bind `_x`
| |
| variable not in all patterns
LL | Err(&(_a, _b, !)),
| ^^ help: use a wildcard `_` instead
error[E0408]: variable `_x` is not bound in all patterns
--> $DIR/bindings.rs:14:19
error: never patterns cannot contain variable bindings
--> $DIR/bindings.rs:16:19
|
LL | let (Ok(_x) | Err(&!)) = x;
| -- ^^^^^^^ pattern doesn't bind `_x`
| |
| variable not in all patterns
LL | Err(&(_a, _b, !)),
| ^^ help: use a wildcard `_` instead
error[E0408]: variable `_a` is not bound in all patterns
--> $DIR/bindings.rs:23:9
error: never patterns cannot contain variable bindings
--> $DIR/bindings.rs:21:25
|
LL | Ok(_ok) | Err(&(_a, _b, !)) => {}
| ^^^^^^^ -- variable not in all patterns
| |
| pattern doesn't bind `_a`
| ^^ help: use a wildcard `_` instead
error[E0408]: variable `_b` is not bound in all patterns
--> $DIR/bindings.rs:23:9
error: never patterns cannot contain variable bindings
--> $DIR/bindings.rs:21:29
|
LL | Ok(_ok) | Err(&(_a, _b, !)) => {}
| ^^^^^^^ -- variable not in all patterns
| |
| pattern doesn't bind `_b`
| ^^ help: use a wildcard `_` instead
error[E0408]: variable `_ok` is not bound in all patterns
--> $DIR/bindings.rs:23:19
|
LL | Ok(_ok) | Err(&(_a, _b, !)) => {}
| --- ^^^^^^^^^^^^^^^^^ pattern doesn't bind `_ok`
| |
| variable not in all patterns
error: aborting due to 4 previous errors
error: aborting due to 5 previous errors
For more information about this error, try `rustc --explain E0408`.

1
tests/ui/rfcs/rfc-0000-never_patterns/parse.rs
View File

@ -71,6 +71,7 @@ fn parse(x: Void) {
let ! = x;
let y @ ! = x;
//~^ ERROR: never patterns cannot contain variable bindings
}
fn foo(!: Void) {}

8
tests/ui/rfcs/rfc-0000-never_patterns/parse.stderr
View File

@ -22,6 +22,12 @@ error: top-level or-patterns are not allowed in `let` bindings
LL | let Ok(_) | Err(!) = &res; // Disallowed; see #82048.
| ^^^^^^^^^^^^^^ help: wrap the pattern in parentheses: `(Ok(_) | Err(!))`
error: never patterns cannot contain variable bindings
--> $DIR/parse.rs:73:9
|
LL | let y @ ! = x;
| ^ help: use a wildcard `_` instead
error: a guard on a never pattern will never be run
--> $DIR/parse.rs:31:20
|
@ -40,5 +46,5 @@ error: a guard on a never pattern will never be run
LL | never!() if true,
| ^^^^ help: remove this guard
error: aborting due to 7 previous errors
error: aborting due to 8 previous errors