Invalid suggestion for missing lifetime specifier when using const generics

[plaes]

Given the following code: https://play.rust-lang.org/?version=stable&mode=debug&edition=2021&gist=de3e0cab5a0a3a72f2840b824066f6f1

// OK: fn buggy_const<'a, const N: usize>(_a: &'a Option<[u8; N]>, _f: &str) -> &'a str {
fn buggy_const<const N: usize>(_a: &Option<[u8; N]>, _f: &str) -> &str {
    return "";
}

fn main() {
    buggy_const(&Some([69,69,69,69,0]), "test");
}

The current output is:

2 | fn buggy_const<const N: usize>(_a: &Option<[u8; N]>, _f: &str) -> &str {
  |                                    ----------------      ----     ^ expected named lifetime parameter
  |
  = help: this function's return type contains a borrowed value, but the signature does not say whether it is borrowed from `arr` or `field`
help: consider introducing a named lifetime parameter
  |
2 | fn buggy_const<const 'a, N: usize>(_a: &'a Option<[u8; N]>, _f: &'a str) -> &'a str {
  |                      +++                ++                       ++          ++

Ideally the output should look like:

2 | fn buggy_const<'a, const N: usize>(_a: &'a Option<[u8; N]>, _f: &'a str) -> &'a str {
  |                +++                      ++                       ++          ++

This issue is present with both stable (1.59) and nightly: 1.61.0-nightly -(2022-04-02 76d770ac21d9521db6a9)

[plaes]

So, this is where the suggestion comes from. Unfortunately I can't yet find a place to move the value before the const:

diff --git a/compiler/rustc_resolve/src/late/diagnostics.rs b/compiler/rustc_resolve/src/late/diagnostics.rs
index b05ec654997..af487381702 100644
--- a/compiler/rustc_resolve/src/late/diagnostics.rs
+++ b/compiler/rustc_resolve/src/late/diagnostics.rs
@@ -2166,7 +2166,15 @@ impl<'tcx> LifetimeContext<'_, 'tcx> {
                                     }
                             )
                         }) {
-                            (param.span.shrink_to_lo(), "'a, ".to_string())
+                            match param.kind {
+                                hir::GenericParamKind::Const { .. }  => {
+                                    println!("TODO: {:#?}", param);
+                                    (param.span.shrink_to_lo(), "'a, ".to_string())
+                                },
+                                _ => {
+                                    (param.span.shrink_to_lo(), "'a, ".to_string())
+                                }
+                            }
                         } else {
                             (generics.span, "<'a>".to_string())
                         }