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clubby789clubby789
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Suggest the correct array length on mismatch
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6 files changed

+119
-2
lines changed

6 files changed

+119
-2
lines changed

‎compiler/rustc_infer/src/infer/error_reporting/mod.rs

+65
Original file line numberDiff line numberDiff line change
@@ -64,6 +64,7 @@ use rustc_errors::{Applicability, DiagnosticBuilder, DiagnosticStyledString};
6464
use rustc_hir as hir;
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use rustc_hir::def::DefKind;
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use rustc_hir::def_id::{DefId, LocalDefId};
67+
use rustc_hir::intravisit::Visitor;
6768
use rustc_hir::lang_items::LangItem;
6869
use rustc_hir::Node;
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use rustc_middle::dep_graph::DepContext;
@@ -1975,6 +1976,70 @@ impl<'tcx> TypeErrCtxt<'_, 'tcx> {
19751976
(ty::Bool, ty::Tuple(list)) => if list.len() == 0 {
19761977
self.suggest_let_for_letchains(&mut err, &trace.cause, span);
19771978
}
1979+
(ty::Array(_, _), ty::Array(_, _)) => 'block: {
1980+
let hir = self.tcx.hir();
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let TypeError::FixedArraySize(sz) = terr else {
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break 'block;
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};
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let tykind = match hir.find_by_def_id(trace.cause.body_id) {
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Some(hir::Node::Item(hir::Item {
1986+
kind: hir::ItemKind::Fn(_, _, body_id),
1987+
..
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})) => {
1989+
let body = hir.body(*body_id);
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struct LetVisitor<'v> {
1991+
span: Span,
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result: Option<&'v hir::Ty<'v>>,
1993+
}
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impl<'v> Visitor<'v> for LetVisitor<'v> {
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fn visit_stmt(&mut self, s: &'v hir::Stmt<'v>) {
1996+
if self.result.is_some() {
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return;
1998+
}
1999+
// Find a local statement where the initializer has
2000+
// the same span as the error and the type is specified.
2001+
if let hir::Stmt {
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kind: hir::StmtKind::Local(hir::Local {
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init: Some(hir::Expr {
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span: init_span,
2005+
..
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}),
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ty: Some(array_ty),
2008+
..
2009+
}),
2010+
..
2011+
} = s
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&& init_span == &self.span {
2013+
self.result = Some(*array_ty);
2014+
}
2015+
}
2016+
}
2017+
let mut visitor = LetVisitor {span, result: None};
2018+
visitor.visit_body(body);
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visitor.result.map(|r| &r.peel_refs().kind)
2020+
}
2021+
Some(hir::Node::Item(hir::Item {
2022+
kind: hir::ItemKind::Const(ty, _),
2023+
..
2024+
})) => {
2025+
Some(&ty.peel_refs().kind)
2026+
}
2027+
_ => None
2028+
};
2029+
2030+
if let Some(tykind) = tykind
2031+
&& let hir::TyKind::Array(_, length) = tykind
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&& let hir::ArrayLen::Body(hir::AnonConst { hir_id, .. }) = length
2033+
&& let Some(span) = self.tcx.hir().opt_span(*hir_id)
2034+
{
2035+
err.span_suggestion(
2036+
span,
2037+
"consider specifying the actual array length",
2038+
sz.found,
2039+
Applicability::MaybeIncorrect,
2040+
);
2041+
}
2042+
}
19782043
_ => {}
19792044
}
19802045
}

‎tests/ui/consts/array-literal-len-mismatch.rs

+4
Original file line numberDiff line numberDiff line change
@@ -0,0 +1,4 @@
1+
const NUMBERS: [u8; 3] = [10, 20];
2+
//~^ ERROR mismatched types
3+
//~^^ HELP consider specifying the actual array length
4+
fn main() {}

‎tests/ui/consts/array-literal-len-mismatch.stderr

+11
Original file line numberDiff line numberDiff line change
@@ -0,0 +1,11 @@
1+
error[E0308]: mismatched types
2+
--> $DIR/array-literal-len-mismatch.rs:1:26
3+
|
4+
LL | const NUMBERS: [u8; 3] = [10, 20];
5+
| - ^^^^^^^^ expected an array with a fixed size of 3 elements, found one with 2 elements
6+
| |
7+
| help: consider specifying the actual array length: `2`
8+
9+
error: aborting due to previous error
10+
11+
For more information about this error, try `rustc --explain E0308`.

‎tests/ui/consts/const-array-oob-arith.stderr

+6-2
Original file line numberDiff line numberDiff line change
@@ -2,13 +2,17 @@ error[E0308]: mismatched types
22
--> $DIR/const-array-oob-arith.rs:5:45
33
|
44
LL | const BLUB: [i32; (ARR[0] - 40) as usize] = [5];
5-
| ^^^ expected an array with a fixed size of 2 elements, found one with 1 element
5+
| ---------------------- ^^^ expected an array with a fixed size of 2 elements, found one with 1 element
6+
| |
7+
| help: consider specifying the actual array length: `1`
68

79
error[E0308]: mismatched types
810
--> $DIR/const-array-oob-arith.rs:8:44
911
|
1012
LL | const BOO: [i32; (ARR[0] - 41) as usize] = [5, 99];
11-
| ^^^^^^^ expected an array with a fixed size of 1 element, found one with 2 elements
13+
| ---------------------- ^^^^^^^ expected an array with a fixed size of 1 element, found one with 2 elements
14+
| |
15+
| help: consider specifying the actual array length: `2`
1216

1317
error: aborting due to 2 previous errors
1418

‎tests/ui/inference/array-len-mismatch.rs

+12
Original file line numberDiff line numberDiff line change
@@ -0,0 +1,12 @@
1+
fn returns_arr() -> [u8; 2] {
2+
[1, 2]
3+
}
4+
5+
fn main() {
6+
let wrong: [u8; 3] = [10, 20];
7+
//~^ ERROR mismatched types
8+
//~^^ HELP consider specifying the actual array length
9+
let wrong: [u8; 3] = returns_arr();
10+
//~^ ERROR mismatched types
11+
//~^^ HELP consider specifying the actual array length
12+
}

‎tests/ui/inference/array-len-mismatch.stderr

+21
Original file line numberDiff line numberDiff line change
@@ -0,0 +1,21 @@
1+
error[E0308]: mismatched types
2+
--> $DIR/array-len-mismatch.rs:6:26
3+
|
4+
LL | let wrong: [u8; 3] = [10, 20];
5+
| ------- ^^^^^^^^ expected an array with a fixed size of 3 elements, found one with 2 elements
6+
| | |
7+
| | help: consider specifying the actual array length: `2`
8+
| expected due to this
9+
10+
error[E0308]: mismatched types
11+
--> $DIR/array-len-mismatch.rs:9:26
12+
|
13+
LL | let wrong: [u8; 3] = returns_arr();
14+
| ------- ^^^^^^^^^^^^^ expected an array with a fixed size of 3 elements, found one with 2 elements
15+
| | |
16+
| | help: consider specifying the actual array length: `2`
17+
| expected due to this
18+
19+
error: aborting due to 2 previous errors
20+
21+
For more information about this error, try `rustc --explain E0308`.

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