Start handling pattern types at the HIR -> Ty conversion boundary

Author: oli-obk

compiler/rustc_error_messages/locales/en-US/hir_analysis.ftl

@@ -124,3 +124,6 @@ hir_analysis_linkage_type =
 hir_analysis_auto_deref_reached_recursion_limit = reached the recursion limit while auto-dereferencing `{$ty}`
     .label = deref recursion limit reached
     .help = consider increasing the recursion limit by adding a `#![recursion_limit = "{$suggested_limit}"]` attribute to your crate (`{$crate_name}`)
+
+hir_analysis_pattern_type_wild_pat = "wildcard patterns are not permitted for pattern types"
+    .label = "this type is the same as the inner type without a pattern"

compiler/rustc_hir_analysis/src/astconv/mod.rs

@@ -12,7 +12,7 @@ use crate::bounds::Bounds;
 use crate::collect::HirPlaceholderCollector;
 use crate::errors::{
     AmbiguousLifetimeBound, MultipleRelaxedDefaultBounds, TraitObjectDeclaredWithNoTraits,
-    TypeofReservedKeywordUsed, ValueOfAssociatedStructAlreadySpecified,
+    TypeofReservedKeywordUsed, ValueOfAssociatedStructAlreadySpecified, WildPatTy,
 };
 use crate::middle::resolve_lifetime as rl;
 use crate::require_c_abi_if_c_variadic;
@@ -2961,7 +2961,23 @@ impl<'o, 'tcx> dyn AstConv<'tcx> + 'o {
                 // handled specially and will not descend into this routine.
                 self.ty_infer(None, ast_ty.span)
             }
-            hir::TyKind::Pat(..) => span_bug!(ast_ty.span, "{ast_ty:#?}"),
+            hir::TyKind::Pat(_ty, pat) => match pat.kind {
+                hir::PatKind::Wild => {
+                    let err = tcx.sess.emit_err(WildPatTy { span: pat.span });
+                    tcx.ty_error_with_guaranteed(err)
+                }
+                hir::PatKind::Binding(_, _, _, _) => todo!(),
+                hir::PatKind::Struct(_, _, _) => todo!(),
+                hir::PatKind::TupleStruct(_, _, _) => todo!(),
+                hir::PatKind::Or(_) => todo!(),
+                hir::PatKind::Path(_) => todo!(),
+                hir::PatKind::Tuple(_, _) => todo!(),
+                hir::PatKind::Box(_) => todo!(),
+                hir::PatKind::Ref(_, _) => todo!(),
+                hir::PatKind::Lit(_) => todo!(),
+                hir::PatKind::Range(_, _, _) => tcx.ty_error(),
+                hir::PatKind::Slice(_, _, _) => todo!(),
+            },
             hir::TyKind::Err => tcx.ty_error(),
         };
 

compiler/rustc_hir_analysis/src/errors.rs

@@ -6,6 +6,10 @@ use rustc_macros::{Diagnostic, LintDiagnostic};
 use rustc_middle::ty::Ty;
 use rustc_span::{symbol::Ident, Span, Symbol};
 
+mod pattern_types;
+
+pub use pattern_types::*;
+
 #[derive(Diagnostic)]
 #[diag(hir_analysis_unrecognized_atomic_operation, code = "E0092")]
 pub struct UnrecognizedAtomicOperation<'a> {

compiler/rustc_hir_analysis/src/errors/pattern_types.rs

@@ -0,0 +1,9 @@
+use rustc_macros::Diagnostic;
+use rustc_span::Span;
+
+#[derive(Diagnostic)]
+#[diag(hir_analysis_pattern_type_wild_pat)]
+pub struct WildPatTy {
+    #[primary_span]
+    pub span: Span,
+}

tests/ui/type/pattern_types/bad_pat.rs

@@ -1,8 +1,10 @@
-// compile-flags: -Zno-analysis
-
 #![feature(pattern_types)]
 
 type NonNullU32_2 = u32 is 1..=;
 //~^ ERROR: inclusive range with no end
 type Positive2 = i32 is 0..=;
 //~^ ERROR: inclusive range with no end
+type Wild = () is _;
+//~^ ERROR: wildcard patterns are not permitted for pattern types
+
+fn main() {}

tests/ui/type/pattern_types/bad_pat.stderr

@@ -1,19 +1,25 @@
 error[E0586]: inclusive range with no end
-  --> $DIR/bad_pat.rs:5:29
+  --> $DIR/bad_pat.rs:3:29
    |
 LL | type NonNullU32_2 = u32 is 1..=;
    |                             ^^^ help: use `..` instead
    |
    = note: inclusive ranges must be bounded at the end (`..=b` or `a..=b`)
 
 error[E0586]: inclusive range with no end
-  --> $DIR/bad_pat.rs:7:26
+  --> $DIR/bad_pat.rs:5:26
    |
 LL | type Positive2 = i32 is 0..=;
    |                          ^^^ help: use `..` instead
    |
    = note: inclusive ranges must be bounded at the end (`..=b` or `a..=b`)
 
-error: aborting due to 2 previous errors
+error: "wildcard patterns are not permitted for pattern types"
+  --> $DIR/bad_pat.rs:7:19
+   |
+LL | type Wild = () is _;
+   |                   ^
+
+error: aborting due to 3 previous errors
 
 For more information about this error, try `rustc --explain E0586`.