Add pattern types to ast

compiler/rustc_ast/src/ast.rs

@@ -2152,6 +2152,9 @@ pub enum TyKind {
     MacCall(P<MacCall>),
     /// Placeholder for a `va_list`.
     CVarArgs,
+    /// Pattern types like `u32 as 1..=`, which is the same as `NonZeroU32`,
+    /// just as part of the type system.
+    Pat(P<Ty>, P<Pat>),
     /// Sometimes we need a dummy value when no error has occurred.
     Dummy,
     /// Placeholder for a kind that has failed to be defined.

compiler/rustc_ast/src/mut_visit.rs

@@ -502,6 +502,10 @@ pub fn noop_visit_ty<T: MutVisitor>(ty: &mut P<Ty>, vis: &mut T) {
         }
         TyKind::Tup(tys) => visit_thin_vec(tys, |ty| vis.visit_ty(ty)),
         TyKind::Paren(ty) => vis.visit_ty(ty),
+        TyKind::Pat(ty, pat) => {
+            vis.visit_ty(ty);
+            vis.visit_pat(pat);
+        }
         TyKind::Path(qself, path) => {
             vis.visit_qself(qself);
             vis.visit_path(path);

compiler/rustc_ast/src/visit.rs

@@ -446,6 +446,10 @@ pub fn walk_ty<'a, V: Visitor<'a>>(visitor: &mut V, typ: &'a Ty) -> V::Result {
             }
             try_visit!(visitor.visit_path(path, typ.id));
         }
+        TyKind::Pat(ty, pat) => {
+            try_visit!(visitor.visit_ty(ty));
+            try_visit!(visitor.visit_pat(pat));
+        }
         TyKind::Array(ty, length) => {
             try_visit!(visitor.visit_ty(ty));
             try_visit!(visitor.visit_anon_const(length));

compiler/rustc_ast_lowering/src/lib.rs

@@ -1463,7 +1463,9 @@ fn lower_ty_direct(&mut self, t: &Ty, itctx: ImplTraitContext) -> hir::Ty<'hir>
                     }
                 }
             }
-            TyKind::MacCall(_) => panic!("`TyKind::MacCall` should have been expanded by now"),
+            TyKind::MacCall(_) => {
+                span_bug!(t.span, "`TyKind::MacCall` should have been expanded by now")
+            }
             TyKind::CVarArgs => {
                 let guar = self.dcx().span_delayed_bug(
                     t.span,
@@ -1471,6 +1473,7 @@ fn lower_ty_direct(&mut self, t: &Ty, itctx: ImplTraitContext) -> hir::Ty<'hir>
                 );
                 hir::TyKind::Err(guar)
             }
+            TyKind::Pat(..) => span_bug!(t.span, "pattern types are unimplemented"),
             TyKind::Dummy => panic!("`TyKind::Dummy` should never be lowered"),
         };
 

compiler/rustc_ast_pretty/src/pprust/state.rs

@@ -1188,6 +1188,11 @@ pub fn print_type(&mut self, ty: &ast::Ty) {
             ast::TyKind::CVarArgs => {
                 self.word("...");
             }
+            ast::TyKind::Pat(ty, pat) => {
+                self.print_type(ty);
+                self.word(" is ");
+                self.print_pat(pat);
+            }
         }
         self.end();
     }

compiler/rustc_passes/src/hir_stats.rs

@@ -611,6 +611,7 @@ fn visit_ty(&mut self, t: &'v ast::Ty) {
                 AnonStruct,
                 AnonUnion,
                 Path,
+                Pat,
                 TraitObject,
                 ImplTrait,
                 Paren,

src/tools/rustfmt/src/types.rs

@@ -867,6 +867,11 @@ fn rewrite(&self, context: &RewriteContext<'_>, shape: Shape) -> Option<String>
                 self.span,
                 shape,
             ),
+            ast::TyKind::Pat(ref ty, ref pat) => {
+                let ty = ty.rewrite(context, shape)?;
+                let pat = pat.rewrite(context, shape)?;
+                Some(format!("{ty} is {pat}"))
+            }
         }
     }
 }