diff --git a/compiler/rustc_typeck/src/astconv/generics.rs b/compiler/rustc_typeck/src/astconv/generics.rs index 0db5fda272a26..b7e77f389f857 100644 --- a/compiler/rustc_typeck/src/astconv/generics.rs +++ b/compiler/rustc_typeck/src/astconv/generics.rs @@ -44,6 +44,13 @@ impl<'o, 'tcx> dyn AstConv<'tcx> + 'o { // the match is non-exhaustive. _ => bug!("invalid generic parameter kind {}", kind), }; + + if let ParamKindOrd::Const { .. } = kind_ord { + if let GenericArg::Type(hir::Ty { kind: hir::TyKind::Infer, .. }) = arg { + err.help("const arguments cannot yet be inferred with `_`"); + } + } + let arg_ord = match arg { GenericArg::Lifetime(_) => ParamKindOrd::Lifetime, GenericArg::Type(_) => ParamKindOrd::Type, diff --git a/src/test/ui/const-generics/issues/issue-62878.full.stderr b/src/test/ui/const-generics/issues/issue-62878.full.stderr index fc70be404971e..dce2e27c71a13 100644 --- a/src/test/ui/const-generics/issues/issue-62878.full.stderr +++ b/src/test/ui/const-generics/issues/issue-62878.full.stderr @@ -9,6 +9,8 @@ error[E0747]: type provided when a constant was expected | LL | foo::<_, {[1]}>(); | ^ + | + = help: const arguments cannot yet be inferred with `_` error[E0308]: mismatched types --> $DIR/issue-62878.rs:11:15 diff --git a/src/test/ui/const-generics/min_const_generics/inferred_const.rs b/src/test/ui/const-generics/min_const_generics/inferred_const.rs new file mode 100644 index 0000000000000..dcd069ce3b0f4 --- /dev/null +++ b/src/test/ui/const-generics/min_const_generics/inferred_const.rs @@ -0,0 +1,8 @@ +#![feature(min_const_generics)] +fn foo(data: [u32; N]) -> [u32; K] { + [0; K] +} +fn main() { + let a = foo::<_, 2>([0, 1, 2]); + //~^ ERROR type provided when a constant was expected +} diff --git a/src/test/ui/const-generics/min_const_generics/inferred_const.stderr b/src/test/ui/const-generics/min_const_generics/inferred_const.stderr new file mode 100644 index 0000000000000..e17105b2aa999 --- /dev/null +++ b/src/test/ui/const-generics/min_const_generics/inferred_const.stderr @@ -0,0 +1,11 @@ +error[E0747]: type provided when a constant was expected + --> $DIR/inferred_const.rs:6:19 + | +LL | let a = foo::<_, 2>([0, 1, 2]); + | ^ + | + = help: const arguments cannot yet be inferred with `_` + +error: aborting due to previous error + +For more information about this error, try `rustc --explain E0747`.