Just totally fully deny late-bound consts

5 files changed, 32 insertions, 6 deletions

diff --git a/compiler/rustc_ast_passes/messages.ftl b/compiler/rustc_ast_passes/messages.ftl
index 8f7dd774207..ca0b7f2ac3a 100644
--- a/compiler/rustc_ast_passes/messages.ftl
+++ b/compiler/rustc_ast_passes/messages.ftl
@@ -120,6 +120,9 @@ ast_passes_fn_without_body =
 ast_passes_forbidden_bound =
     bounds cannot be used in this context
 
+ast_passes_forbidden_const_param =
+    late-bound const parameters cannot be used currently
+
 ast_passes_forbidden_default =
     `default` is only allowed on items in trait impls
     .label = `default` because of this
diff --git a/compiler/rustc_ast_passes/src/errors.rs b/compiler/rustc_ast_passes/src/errors.rs
index 783bca6b695..215ccd2ab4d 100644
--- a/compiler/rustc_ast_passes/src/errors.rs
+++ b/compiler/rustc_ast_passes/src/errors.rs
@@ -70,6 +70,13 @@ pub struct ForbiddenBound {
 }
 
 #[derive(Diagnostic)]
+#[diag(ast_passes_forbidden_const_param)]
+pub struct ForbiddenConstParam {
+    #[primary_span]
+    pub const_param_spans: Vec<Span>,
+}
+
+#[derive(Diagnostic)]
 #[diag(ast_passes_fn_param_too_many)]
 pub struct FnParamTooMany {
     #[primary_span]
diff --git a/compiler/rustc_ast_passes/src/feature_gate.rs b/compiler/rustc_ast_passes/src/feature_gate.rs
index 2178b65727d..e91dfb27766 100644
--- a/compiler/rustc_ast_passes/src/feature_gate.rs
+++ b/compiler/rustc_ast_passes/src/feature_gate.rs
@@ -162,6 +162,22 @@ impl<'a> PostExpansionVisitor<'a> {
             crate::fluent_generated::ast_passes_forbidden_non_lifetime_param
         );
 
+        // FIXME(non_lifetime_binders): Const bound params are pretty broken.
+        // Let's keep users from using this feature accidentally.
+        if self.features.non_lifetime_binders {
+            let const_param_spans: Vec<_> = params
+                .iter()
+                .filter_map(|param| match param.kind {
+                    ast::GenericParamKind::Const { .. } => Some(param.ident.span),
+                    _ => None,
+                })
+                .collect();
+
+            if !const_param_spans.is_empty() {
+                self.sess.dcx().emit_err(errors::ForbiddenConstParam { const_param_spans });
+            }
+        }
+
         for param in params {
             if !param.bounds.is_empty() {
                 let spans: Vec<_> = param.bounds.iter().map(|b| b.span()).collect();
diff --git a/compiler/rustc_hir_analysis/src/collect/resolve_bound_vars.rs b/compiler/rustc_hir_analysis/src/collect/resolve_bound_vars.rs
index 7930f54038d..349dc9ad00e 100644
--- a/compiler/rustc_hir_analysis/src/collect/resolve_bound_vars.rs
+++ b/compiler/rustc_hir_analysis/src/collect/resolve_bound_vars.rs
@@ -2094,11 +2094,7 @@ pub fn deny_non_region_late_bound(
             format!("late-bound {what} parameter not allowed on {where_}"),
         );
 
-        let guar = if tcx.features().non_lifetime_binders && first {
-            diag.emit()
-        } else {
-            diag.delay_as_bug()
-        };
+        let guar = diag.emit_unless(!tcx.features().non_lifetime_binders || !first);
 
         first = false;
         *arg = ResolvedArg::Error(guar);
diff --git a/compiler/rustc_resolve/src/late.rs b/compiler/rustc_resolve/src/late.rs
index dc7200465d9..51414d78596 100644
--- a/compiler/rustc_resolve/src/late.rs
+++ b/compiler/rustc_resolve/src/late.rs
@@ -2763,7 +2763,11 @@ impl<'a: 'ast, 'b, 'ast, 'tcx> LateResolutionVisitor<'a, 'b, 'ast, 'tcx> {
             let res = match kind {
                 RibKind::Item(..) | RibKind::AssocItem => Res::Def(def_kind, def_id.to_def_id()),
                 RibKind::Normal => {
-                    if self.r.tcx.features().non_lifetime_binders {
+                    // FIXME(non_lifetime_binders): Stop special-casing
+                    // const params to error out here.
+                    if self.r.tcx.features().non_lifetime_binders
+                        && matches!(param.kind, GenericParamKind::Type { .. })
+                    {
                         Res::Def(def_kind, def_id.to_def_id())
                     } else {
                         Res::Err