Rollup merge of #111670 - compiler-errors:const-param-ty, r=BoxyUwU

Require that const param tys implement `ConstParamTy`

1. Require that const param tys implement `ConstParamTy` instead of using `search_for_adt_const_param_violation`
2. Add `StructuralPartialEq` as a supertrait for `ConstParamTy`, since we need to make sure that we derive *both* `PartialEq` and `Eq`
3. Implement `ConstParamTy` for tuples up to 12 (or whatever the default for tuples is)
4. Add some custom diagnostics to `ConstParamTy` errors, to avoid regressions from (1.). It's still not as great as it could be -- will point out inline in comments.

r? `@BoxyUwU`

2 files changed, 9 insertions, 26 deletions

diff --git a/compiler/rustc_errors/src/diagnostic_builder.rs b/compiler/rustc_errors/src/diagnostic_builder.rs
index 7d9d0c76450..08ff2cfba5c 100644
--- a/compiler/rustc_errors/src/diagnostic_builder.rs
+++ b/compiler/rustc_errors/src/diagnostic_builder.rs
@@ -115,36 +115,22 @@ pub trait EmissionGuarantee: Sized {
     ) -> DiagnosticBuilder<'_, Self>;
 }
 
-/// Private module for sealing the `IsError` helper trait.
-mod sealed_level_is_error {
-    use crate::Level;
-
-    /// Sealed helper trait for statically checking that a `Level` is an error.
-    pub(crate) trait IsError<const L: Level> {}
-
-    impl IsError<{ Level::Bug }> for () {}
-    impl IsError<{ Level::DelayedBug }> for () {}
-    impl IsError<{ Level::Fatal }> for () {}
-    // NOTE(eddyb) `Level::Error { lint: true }` is also an error, but lints
-    // don't need error guarantees, as their levels are always dynamic.
-    impl IsError<{ Level::Error { lint: false } }> for () {}
-}
-
 impl<'a> DiagnosticBuilder<'a, ErrorGuaranteed> {
     /// Convenience function for internal use, clients should use one of the
     /// `struct_*` methods on [`Handler`].
     #[track_caller]
-    pub(crate) fn new_guaranteeing_error<M: Into<DiagnosticMessage>, const L: Level>(
+    pub(crate) fn new_guaranteeing_error<M: Into<DiagnosticMessage>>(
         handler: &'a Handler,
         message: M,
-    ) -> Self
-    where
-        (): sealed_level_is_error::IsError<L>,
-    {
+    ) -> Self {
         Self {
             inner: DiagnosticBuilderInner {
                 state: DiagnosticBuilderState::Emittable(handler),
-                diagnostic: Box::new(Diagnostic::new_with_code(L, None, message)),
+                diagnostic: Box::new(Diagnostic::new_with_code(
+                    Level::Error { lint: false },
+                    None,
+                    message,
+                )),
             },
             _marker: PhantomData,
         }
@@ -203,9 +189,7 @@ impl EmissionGuarantee for ErrorGuaranteed {
         handler: &Handler,
         msg: impl Into<DiagnosticMessage>,
     ) -> DiagnosticBuilder<'_, Self> {
-        DiagnosticBuilder::new_guaranteeing_error::<_, { Level::Error { lint: false } }>(
-            handler, msg,
-        )
+        DiagnosticBuilder::new_guaranteeing_error(handler, msg)
     }
 }
 
diff --git a/compiler/rustc_errors/src/lib.rs b/compiler/rustc_errors/src/lib.rs
index 6c5f3e62454..bf77ed81f9b 100644
--- a/compiler/rustc_errors/src/lib.rs
+++ b/compiler/rustc_errors/src/lib.rs
@@ -6,7 +6,6 @@
 #![feature(array_windows)]
 #![feature(drain_filter)]
 #![feature(if_let_guard)]
-#![feature(adt_const_params)]
 #![feature(let_chains)]
 #![feature(never_type)]
 #![feature(result_option_inspect)]
@@ -845,7 +844,7 @@ impl Handler {
         &self,
         msg: impl Into<DiagnosticMessage>,
     ) -> DiagnosticBuilder<'_, ErrorGuaranteed> {
-        DiagnosticBuilder::new_guaranteeing_error::<_, { Level::Error { lint: false } }>(self, msg)
+        DiagnosticBuilder::new_guaranteeing_error(self, msg)
     }
 
     /// This should only be used by `rustc_middle::lint::struct_lint_level`. Do not use it for hard errors.