Add pattern types to ast

Author: oli-obk

compiler/rustc_ast/src/ast.rs

@@ -2135,6 +2135,9 @@ pub enum TyKind {
     Err,
     /// 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>),
 }
 
 impl TyKind {

compiler/rustc_ast/src/mut_visit.rs

@@ -497,6 +497,10 @@ 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

@@ -436,6 +436,10 @@ pub fn walk_ty<'a, V: Visitor<'a>>(visitor: &mut V, typ: &'a Ty) {
             }
             visitor.visit_path(path, typ.id);
         }
+        TyKind::Pat(ty, pat) => {
+            visitor.visit_ty(ty);
+            visitor.visit_pat(pat);
+        }
         TyKind::Array(ty, length) => {
             visitor.visit_ty(ty);
             visitor.visit_anon_const(length)

compiler/rustc_ast_lowering/src/lib.rs

@@ -1521,14 +1521,17 @@ impl<'a, 'hir> LoweringContext<'a, '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,
                     "`TyKind::CVarArgs` should have been handled elsewhere",
                 );
                 hir::TyKind::Err(guar)
             }
+            TyKind::Pat(..) => span_bug!(t.span, "pattern types are unimplemented"),
         };
 
         hir::Ty { kind, span: self.lower_span(t.span), hir_id: self.lower_node_id(t.id) }

compiler/rustc_ast_pretty/src/pprust/state.rs

@@ -1046,6 +1046,11 @@ impl<'a> State<'a> {
             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

@@ -613,6 +613,7 @@ impl<'v> ast_visit::Visitor<'v> for StatCollector<'v> {
                 AnonStruct,
                 AnonUnion,
                 Path,
+                Pat,
                 TraitObject,
                 ImplTrait,
                 Paren,

src/tools/rustfmt/src/types.rs

@@ -856,6 +856,11 @@ impl Rewrite for ast::Ty {
                 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}"))
+            }
         }
     }
 }