Rollup merge of #131038 - onkoe:fix/adt_const_params_leak_118179, r=compiler-errors

Fix `adt_const_params` leaking `{type error}` in error msg

Fixes the confusing diagnostic described in #118179. (users would see `{type error}` in some situations, which is pretty weird)

`adt_const_params` tracking issue: #95174

Author: matthiaskrgr

compiler/rustc_hir_analysis/src/check/wfcheck.rs

@@ -961,13 +961,20 @@ fn check_param_wf(tcx: TyCtxt<'_>, param: &hir::GenericParam<'_>) -> Result<(),
                         hir_ty.span,
                         "using raw pointers as const generic parameters is forbidden",
                     ),
-                    _ => tcx.dcx().struct_span_err(
-                        hir_ty.span,
-                        format!("`{}` is forbidden as the type of a const generic parameter", ty),
-                    ),
+                    _ => {
+                        // Avoid showing "{type error}" to users. See #118179.
+                        ty.error_reported()?;
+
+                        tcx.dcx().struct_span_err(
+                            hir_ty.span,
+                            format!(
+                                "`{ty}` is forbidden as the type of a const generic parameter",
+                            ),
+                        )
+                    }
                 };
 
-                diag.note("the only supported types are integers, `bool` and `char`");
+                diag.note("the only supported types are integers, `bool`, and `char`");
 
                 let cause = ObligationCause::misc(hir_ty.span, param.def_id);
                 let adt_const_params_feature_string =

tests/ui/const-generics/adt_const_params/suggest_feature_only_when_possible.stderr

@@ -4,15 +4,15 @@ error: `&'static mut ()` is forbidden as the type of a const generic parameter
 LL | fn uwu_0<const N: &'static mut ()>() {}
    |                   ^^^^^^^^^^^^^^^
    |
-   = note: the only supported types are integers, `bool` and `char`
+   = note: the only supported types are integers, `bool`, and `char`
 
 error: `&'static u32` is forbidden as the type of a const generic parameter
   --> $DIR/suggest_feature_only_when_possible.rs:15:19
    |
 LL | fn owo_0<const N: &'static u32>() {}
    |                   ^^^^^^^^^^^^
    |
-   = note: the only supported types are integers, `bool` and `char`
+   = note: the only supported types are integers, `bool`, and `char`
 help: add `#![feature(adt_const_params)]` to the crate attributes to enable more complex and user defined types
    |
 LL + #![feature(adt_const_params)]
@@ -28,7 +28,7 @@ error: `Meow` is forbidden as the type of a const generic parameter
 LL | fn meow_0<const N: Meow>() {}
    |                    ^^^^
    |
-   = note: the only supported types are integers, `bool` and `char`
+   = note: the only supported types are integers, `bool`, and `char`
 help: add `#![feature(adt_const_params)]` to the crate attributes to enable more complex and user defined types
    |
 LL + #![feature(adt_const_params)]
@@ -40,7 +40,7 @@ error: `&'static Meow` is forbidden as the type of a const generic parameter
 LL | fn meow_1<const N: &'static Meow>() {}
    |                    ^^^^^^^^^^^^^
    |
-   = note: the only supported types are integers, `bool` and `char`
+   = note: the only supported types are integers, `bool`, and `char`
 help: add `#![feature(adt_const_params)]` to the crate attributes to enable more complex and user defined types
    |
 LL + #![feature(adt_const_params)]
@@ -56,39 +56,39 @@ error: `[Meow; 100]` is forbidden as the type of a const generic parameter
 LL | fn meow_2<const N: [Meow; 100]>() {}
    |                    ^^^^^^^^^^^
    |
-   = note: the only supported types are integers, `bool` and `char`
+   = note: the only supported types are integers, `bool`, and `char`
 
 error: `(Meow, u8)` is forbidden as the type of a const generic parameter
   --> $DIR/suggest_feature_only_when_possible.rs:29:20
    |
 LL | fn meow_3<const N: (Meow, u8)>() {}
    |                    ^^^^^^^^^^
    |
-   = note: the only supported types are integers, `bool` and `char`
+   = note: the only supported types are integers, `bool`, and `char`
 
 error: `(Meow, String)` is forbidden as the type of a const generic parameter
   --> $DIR/suggest_feature_only_when_possible.rs:34:20
    |
 LL | fn meow_4<const N: (Meow, String)>() {}
    |                    ^^^^^^^^^^^^^^
    |
-   = note: the only supported types are integers, `bool` and `char`
+   = note: the only supported types are integers, `bool`, and `char`
 
 error: `String` is forbidden as the type of a const generic parameter
   --> $DIR/suggest_feature_only_when_possible.rs:38:19
    |
 LL | fn nya_0<const N: String>() {}
    |                   ^^^^^^
    |
-   = note: the only supported types are integers, `bool` and `char`
+   = note: the only supported types are integers, `bool`, and `char`
 
 error: `Vec<u32>` is forbidden as the type of a const generic parameter
   --> $DIR/suggest_feature_only_when_possible.rs:40:19
    |
 LL | fn nya_1<const N: Vec<u32>>() {}
    |                   ^^^^^^^^
    |
-   = note: the only supported types are integers, `bool` and `char`
+   = note: the only supported types are integers, `bool`, and `char`
 
 error: aborting due to 9 previous errors