diff --git a/compiler/rustc_infer/src/infer/error_reporting/mod.rs b/compiler/rustc_infer/src/infer/error_reporting/mod.rs
index 88a0d6def5ec2..e60c86aed012c 100644
--- a/compiler/rustc_infer/src/infer/error_reporting/mod.rs
+++ b/compiler/rustc_infer/src/infer/error_reporting/mod.rs
@@ -64,6 +64,7 @@ use rustc_errors::{Applicability, DiagnosticBuilder, DiagnosticStyledString};
use rustc_hir as hir;
use rustc_hir::def::DefKind;
use rustc_hir::def_id::{DefId, LocalDefId};
+use rustc_hir::intravisit::Visitor;
use rustc_hir::lang_items::LangItem;
use rustc_hir::Node;
use rustc_middle::dep_graph::DepContext;
@@ -1975,6 +1976,70 @@ impl<'tcx> TypeErrCtxt<'_, 'tcx> {
(ty::Bool, ty::Tuple(list)) => if list.len() == 0 {
self.suggest_let_for_letchains(&mut err, &trace.cause, span);
}
+ (ty::Array(_, _), ty::Array(_, _)) => 'block: {
+ let hir = self.tcx.hir();
+ let TypeError::FixedArraySize(sz) = terr else {
+ break 'block;
+ };
+ let tykind = match hir.find_by_def_id(trace.cause.body_id) {
+ Some(hir::Node::Item(hir::Item {
+ kind: hir::ItemKind::Fn(_, _, body_id),
+ ..
+ })) => {
+ let body = hir.body(*body_id);
+ struct LetVisitor<'v> {
+ span: Span,
+ result: Option<&'v hir::Ty<'v>>,
+ }
+ impl<'v> Visitor<'v> for LetVisitor<'v> {
+ fn visit_stmt(&mut self, s: &'v hir::Stmt<'v>) {
+ if self.result.is_some() {
+ return;
+ }
+ // Find a local statement where the initializer has
+ // the same span as the error and the type is specified.
+ if let hir::Stmt {
+ kind: hir::StmtKind::Local(hir::Local {
+ init: Some(hir::Expr {
+ span: init_span,
+ ..
+ }),
+ ty: Some(array_ty),
+ ..
+ }),
+ ..
+ } = s
+ && init_span == &self.span {
+ self.result = Some(*array_ty);
+ }
+ }
+ }
+ let mut visitor = LetVisitor {span, result: None};
+ visitor.visit_body(body);
+ visitor.result.map(|r| &r.peel_refs().kind)
+ }
+ Some(hir::Node::Item(hir::Item {
+ kind: hir::ItemKind::Const(ty, _),
+ ..
+ })) => {
+ Some(&ty.peel_refs().kind)
+ }
+ _ => None
+ };
+
+ if let Some(tykind) = tykind
+ && let hir::TyKind::Array(_, length) = tykind
+ && let hir::ArrayLen::Body(hir::AnonConst { hir_id, .. }) = length
+ && let Some(span) = self.tcx.hir().opt_span(*hir_id)
+ {
+ err.span_suggestion(
+ span,
+ "consider specifying the actual array length",
+ sz.found,
+ Applicability::MaybeIncorrect,
+ );
+ }
+ }
_ => {}
}
}
diff --git a/tests/ui/consts/array-literal-len-mismatch.rs b/tests/ui/consts/array-literal-len-mismatch.rs
new file mode 100644
index 0000000000000..b30ff61a99c53
--- /dev/null
+++ b/tests/ui/consts/array-literal-len-mismatch.rs
@@ -0,0 +1,4 @@
+const NUMBERS: [u8; 3] = [10, 20];
+//~^ ERROR mismatched types
+//~^^ HELP consider specifying the actual array length
+fn main() {}
diff --git a/tests/ui/consts/array-literal-len-mismatch.stderr b/tests/ui/consts/array-literal-len-mismatch.stderr
new file mode 100644
index 0000000000000..22fec638970a7
--- /dev/null
+++ b/tests/ui/consts/array-literal-len-mismatch.stderr
@@ -0,0 +1,11 @@
+error[E0308]: mismatched types
+ --> $DIR/array-literal-len-mismatch.rs:1:26
+ |
+LL | const NUMBERS: [u8; 3] = [10, 20];
+ | - ^^^^^^^^ expected an array with a fixed size of 3 elements, found one with 2 elements
+ | |
+ | help: consider specifying the actual array length: `2`
+
+error: aborting due to previous error
+
+For more information about this error, try `rustc --explain E0308`.
diff --git a/tests/ui/consts/const-array-oob-arith.stderr b/tests/ui/consts/const-array-oob-arith.stderr
index f7a55d3ca7210..029d94273fae1 100644
--- a/tests/ui/consts/const-array-oob-arith.stderr
+++ b/tests/ui/consts/const-array-oob-arith.stderr
@@ -2,13 +2,17 @@ error[E0308]: mismatched types
--> $DIR/const-array-oob-arith.rs:5:45
|
LL | const BLUB: [i32; (ARR[0] - 40) as usize] = [5];
- | ^^^ expected an array with a fixed size of 2 elements, found one with 1 element
+ | ---------------------- ^^^ expected an array with a fixed size of 2 elements, found one with 1 element
+ | |
+ | help: consider specifying the actual array length: `1`
error[E0308]: mismatched types
--> $DIR/const-array-oob-arith.rs:8:44
|
LL | const BOO: [i32; (ARR[0] - 41) as usize] = [5, 99];
- | ^^^^^^^ expected an array with a fixed size of 1 element, found one with 2 elements
+ | ---------------------- ^^^^^^^ expected an array with a fixed size of 1 element, found one with 2 elements
+ | |
+ | help: consider specifying the actual array length: `2`
error: aborting due to 2 previous errors
diff --git a/tests/ui/inference/array-len-mismatch.rs b/tests/ui/inference/array-len-mismatch.rs
new file mode 100644
index 0000000000000..149d061029bc3
--- /dev/null
+++ b/tests/ui/inference/array-len-mismatch.rs
@@ -0,0 +1,12 @@
+fn returns_arr() -> [u8; 2] {
+ [1, 2]
+}
+
+fn main() {
+ let wrong: [u8; 3] = [10, 20];
+ //~^ ERROR mismatched types
+ //~^^ HELP consider specifying the actual array length
+ let wrong: [u8; 3] = returns_arr();
+ //~^ ERROR mismatched types
+ //~^^ HELP consider specifying the actual array length
+}
diff --git a/tests/ui/inference/array-len-mismatch.stderr b/tests/ui/inference/array-len-mismatch.stderr
new file mode 100644
index 0000000000000..7358e47839725
--- /dev/null
+++ b/tests/ui/inference/array-len-mismatch.stderr
@@ -0,0 +1,21 @@
+error[E0308]: mismatched types
+ --> $DIR/array-len-mismatch.rs:6:26
+ |
+LL | let wrong: [u8; 3] = [10, 20];
+ | ------- ^^^^^^^^ expected an array with a fixed size of 3 elements, found one with 2 elements
+ | | |
+ | | help: consider specifying the actual array length: `2`
+ | expected due to this
+
+error[E0308]: mismatched types
+ --> $DIR/array-len-mismatch.rs:9:26
+ |
+LL | let wrong: [u8; 3] = returns_arr();
+ | ------- ^^^^^^^^^^^^^ expected an array with a fixed size of 3 elements, found one with 2 elements
+ | | |
+ | | help: consider specifying the actual array length: `2`
+ | expected due to this
+
+error: aborting due to 2 previous errors
+
+For more information about this error, try `rustc --explain E0308`.