diff --git a/compiler/rustc_infer/src/infer/error_reporting/need_type_info.rs b/compiler/rustc_infer/src/infer/error_reporting/need_type_info.rs
index fd8f46a6926..373f0a602c0 100644
--- a/compiler/rustc_infer/src/infer/error_reporting/need_type_info.rs
+++ b/compiler/rustc_infer/src/infer/error_reporting/need_type_info.rs
@@ -124,6 +124,11 @@ impl<'a, 'tcx> Visitor<'tcx> for FindHirNodeVisitor<'a, 'tcx> {
return;
}
}
+
+ // FIXME(const_generics): Currently, any uninferred `const` generics arguments
+ // are handled specially, but instead they should be handled in `annotate_method_call`,
+ // which currently doesn't work because this evaluates to `false` for const arguments.
+ // See https://github.com/rust-lang/rust/pull/77758 for more details.
if self.node_ty_contains_target(expr.hir_id).is_some() {
match expr.kind {
ExprKind::Closure(..) => self.found_closure = Some(&expr),
@@ -345,11 +350,6 @@ impl<'a, 'tcx> InferCtxt<'a, 'tcx> {
) -> DiagnosticBuilder<'tcx> {
let arg = self.resolve_vars_if_possible(arg);
let arg_data = self.extract_inference_diagnostics_data(arg, None);
- let kind_str = match arg.unpack() {
- GenericArgKind::Type(_) => "type",
- GenericArgKind::Const(_) => "the value",
- GenericArgKind::Lifetime(_) => bug!("unexpected lifetime"),
- };
let mut local_visitor = FindHirNodeVisitor::new(&self, arg, span);
let ty_to_string = |ty: Ty<'tcx>| -> String {
@@ -618,6 +618,28 @@ impl<'a, 'tcx> InferCtxt<'a, 'tcx> {
.any(|span_label| span_label.label.is_some() && span_label.span == span)
&& local_visitor.found_arg_pattern.is_none()
{
+ let (kind_str, const_value) = match arg.unpack() {
+ GenericArgKind::Type(_) => ("type", None),
+ GenericArgKind::Const(_) => ("the value", Some(())),
+ GenericArgKind::Lifetime(_) => bug!("unexpected lifetime"),
+ };
+
+ // FIXME(const_generics): we would like to handle const arguments
+ // as part of the normal diagnostics flow below, but there appear to
+ // be subtleties in doing so, so for now we special-case const args
+ // here.
+ if let Some(suggestion) = const_value
+ .and_then(|_| arg_data.parent_name.as_ref())
+ .map(|parent| format!("{}::<{}>", parent, arg_data.name))
+ {
+ err.span_suggestion_verbose(
+ span,
+ "consider specifying the const argument",
+ suggestion,
+ Applicability::MaybeIncorrect,
+ );
+ }
+
// Avoid multiple labels pointing at `span`.
err.span_label(
span,
diff --git a/src/test/ui/const-generics/infer/cannot-infer-const-args.full.stderr b/src/test/ui/const-generics/infer/cannot-infer-const-args.full.stderr
index b438ed3ad65..05bf67a5ff7 100644
--- a/src/test/ui/const-generics/infer/cannot-infer-const-args.full.stderr
+++ b/src/test/ui/const-generics/infer/cannot-infer-const-args.full.stderr
@@ -3,6 +3,11 @@ error[E0282]: type annotations needed
|
LL | foo();
| ^^^ cannot infer the value of const parameter `X` declared on the function `foo`
+ |
+help: consider specifying the const argument
+ |
+LL | foo::<X>();
+ | ^^^^^^^^
error: aborting due to previous error
diff --git a/src/test/ui/const-generics/infer/cannot-infer-const-args.min.stderr b/src/test/ui/const-generics/infer/cannot-infer-const-args.min.stderr
index b438ed3ad65..05bf67a5ff7 100644
--- a/src/test/ui/const-generics/infer/cannot-infer-const-args.min.stderr
+++ b/src/test/ui/const-generics/infer/cannot-infer-const-args.min.stderr
@@ -3,6 +3,11 @@ error[E0282]: type annotations needed
|
LL | foo();
| ^^^ cannot infer the value of const parameter `X` declared on the function `foo`
+ |
+help: consider specifying the const argument
+ |
+LL | foo::<X>();
+ | ^^^^^^^^
error: aborting due to previous error
diff --git a/src/test/ui/const-generics/infer/issue-77092.stderr b/src/test/ui/const-generics/infer/issue-77092.stderr
index 63facbf3b8c..99894173bc8 100644
--- a/src/test/ui/const-generics/infer/issue-77092.stderr
+++ b/src/test/ui/const-generics/infer/issue-77092.stderr
@@ -3,6 +3,11 @@ error[E0282]: type annotations needed
|
LL | println!("{:?}", take_array_from_mut(&mut arr, i));
| ^^^^^^^^^^^^^^^^^^^ cannot infer the value of const parameter `N` declared on the function `take_array_from_mut`
+ |
+help: consider specifying the const argument
+ |
+LL | println!("{:?}", take_array_from_mut::<N>(&mut arr, i));
+ | ^^^^^^^^^^^^^^^^^^^^^^^^
error: aborting due to previous error
diff --git a/src/test/ui/const-generics/infer/method-chain.full.stderr b/src/test/ui/const-generics/infer/method-chain.full.stderr
index 1fb0b23cf11..7aa3bd44df8 100644
--- a/src/test/ui/const-generics/infer/method-chain.full.stderr
+++ b/src/test/ui/const-generics/infer/method-chain.full.stderr
@@ -3,6 +3,11 @@ error[E0282]: type annotations needed
|
LL | Foo.bar().bar().bar().bar().baz();
| ^^^ cannot infer the value of const parameter `N` declared on the associated function `baz`
+ |
+help: consider specifying the const argument
+ |
+LL | Foo.bar().bar().bar().bar().baz::<N>();
+ | ^^^^^^^^
error: aborting due to previous error
diff --git a/src/test/ui/const-generics/infer/method-chain.min.stderr b/src/test/ui/const-generics/infer/method-chain.min.stderr
index 1fb0b23cf11..7aa3bd44df8 100644
--- a/src/test/ui/const-generics/infer/method-chain.min.stderr
+++ b/src/test/ui/const-generics/infer/method-chain.min.stderr
@@ -3,6 +3,11 @@ error[E0282]: type annotations needed
|
LL | Foo.bar().bar().bar().bar().baz();
| ^^^ cannot infer the value of const parameter `N` declared on the associated function `baz`
+ |
+help: consider specifying the const argument
+ |
+LL | Foo.bar().bar().bar().bar().baz::<N>();
+ | ^^^^^^^^
error: aborting due to previous error
diff --git a/src/test/ui/const-generics/infer/one-param-uninferred.full.stderr b/src/test/ui/const-generics/infer/one-param-uninferred.full.stderr
new file mode 100644
index 00000000000..cc6c9a47510
--- /dev/null
+++ b/src/test/ui/const-generics/infer/one-param-uninferred.full.stderr
@@ -0,0 +1,14 @@
+error[E0282]: type annotations needed
+ --> $DIR/one-param-uninferred.rs:15:23
+ |
+LL | let _: [u8; 17] = foo();
+ | ^^^ cannot infer the value of const parameter `M` declared on the function `foo`
+ |
+help: consider specifying the const argument
+ |
+LL | let _: [u8; 17] = foo::<M>();
+ | ^^^^^^^^
+
+error: aborting due to previous error
+
+For more information about this error, try `rustc --explain E0282`.
diff --git a/src/test/ui/const-generics/infer/one-param-uninferred.min.stderr b/src/test/ui/const-generics/infer/one-param-uninferred.min.stderr
new file mode 100644
index 00000000000..cc6c9a47510
--- /dev/null
+++ b/src/test/ui/const-generics/infer/one-param-uninferred.min.stderr
@@ -0,0 +1,14 @@
+error[E0282]: type annotations needed
+ --> $DIR/one-param-uninferred.rs:15:23
+ |
+LL | let _: [u8; 17] = foo();
+ | ^^^ cannot infer the value of const parameter `M` declared on the function `foo`
+ |
+help: consider specifying the const argument
+ |
+LL | let _: [u8; 17] = foo::<M>();
+ | ^^^^^^^^
+
+error: aborting due to previous error
+
+For more information about this error, try `rustc --explain E0282`.
diff --git a/src/test/ui/const-generics/infer/one-param-uninferred.rs b/src/test/ui/const-generics/infer/one-param-uninferred.rs
new file mode 100644
index 00000000000..0e947131f4c
--- /dev/null
+++ b/src/test/ui/const-generics/infer/one-param-uninferred.rs
@@ -0,0 +1,17 @@
+// Test that we emit an error if we cannot properly infer a constant.
+// revisions: full min
+
+#![cfg_attr(full, feature(const_generics))]
+#![cfg_attr(full, allow(incomplete_features))]
+#![cfg_attr(min, feature(min_const_generics))]
+
+fn foo<const N: usize, const M: usize>() -> [u8; N] {
+ todo!()
+}
+
+fn main() {
+ // FIXME(const_generics): Currently this only suggests one const parameter,
+ // but instead it should suggest to provide all parameters.
+ let _: [u8; 17] = foo();
+ //~^ ERROR type annotations needed
+}
diff --git a/src/test/ui/const-generics/infer/uninferred-consts.full.stderr b/src/test/ui/const-generics/infer/uninferred-consts.full.stderr
index 7a451903e96..4be625ba909 100644
--- a/src/test/ui/const-generics/infer/uninferred-consts.full.stderr
+++ b/src/test/ui/const-generics/infer/uninferred-consts.full.stderr
@@ -2,7 +2,12 @@ error[E0282]: type annotations needed
--> $DIR/uninferred-consts.rs:14:9
|
LL | Foo.foo();
- | ^^^ cannot infer the value of const parameter `N` declared on the associated function `foo`
+ | ^^^ cannot infer the value of const parameter `A` declared on the associated function `foo`
+ |
+help: consider specifying the const argument
+ |
+LL | Foo.foo::<A>();
+ | ^^^^^^^^
error: aborting due to previous error
diff --git a/src/test/ui/const-generics/infer/uninferred-consts.min.stderr b/src/test/ui/const-generics/infer/uninferred-consts.min.stderr
index 7a451903e96..4be625ba909 100644
--- a/src/test/ui/const-generics/infer/uninferred-consts.min.stderr
+++ b/src/test/ui/const-generics/infer/uninferred-consts.min.stderr
@@ -2,7 +2,12 @@ error[E0282]: type annotations needed
--> $DIR/uninferred-consts.rs:14:9
|
LL | Foo.foo();
- | ^^^ cannot infer the value of const parameter `N` declared on the associated function `foo`
+ | ^^^ cannot infer the value of const parameter `A` declared on the associated function `foo`
+ |
+help: consider specifying the const argument
+ |
+LL | Foo.foo::<A>();
+ | ^^^^^^^^
error: aborting due to previous error
diff --git a/src/test/ui/const-generics/infer/uninferred-consts.rs b/src/test/ui/const-generics/infer/uninferred-consts.rs
index ec5b3ffe544..00fb6eac992 100644
--- a/src/test/ui/const-generics/infer/uninferred-consts.rs
+++ b/src/test/ui/const-generics/infer/uninferred-consts.rs
@@ -8,7 +8,7 @@
// taken from https://github.com/rust-lang/rust/issues/70507#issuecomment-615268893
struct Foo;
impl Foo {
- fn foo<const N: usize>(self) {}
+ fn foo<const A: usize, const B: usize>(self) {}
}
fn main() {
Foo.foo();