Add a TyPat in the AST to reuse the generic arg lowering logic

compiler/rustc_ast/src/ast.rs

@@ -2249,7 +2249,7 @@ pub enum TyKind {
     CVarArgs,
     /// Pattern types like `pattern_type!(u32 is 1..=)`, which is the same as `NonZero<u32>`,
     /// just as part of the type system.
-    Pat(P<Ty>, P<Pat>),
+    Pat(P<Ty>, P<TyPat>),
     /// Sometimes we need a dummy value when no error has occurred.
     Dummy,
     /// Placeholder for a kind that has failed to be defined.
@@ -2277,6 +2277,27 @@ impl TyKind {
     }
 }
 
+/// A pattern type pattern.
+#[derive(Clone, Encodable, Decodable, Debug)]
+pub struct TyPat {
+    pub id: NodeId,
+    pub kind: TyPatKind,
+    pub span: Span,
+    pub tokens: Option<LazyAttrTokenStream>,
+}
+
+/// All the different flavors of pattern that Rust recognizes.
+//
+// Adding a new variant? Please update `test_pat` in `tests/ui/macros/stringify.rs`.
+#[derive(Clone, Encodable, Decodable, Debug)]
+pub enum TyPatKind {
+    /// A range pattern (e.g., `1...2`, `1..2`, `1..`, `..2`, `1..=2`, `..=2`).
+    Range(Option<P<AnonConst>>, Option<P<AnonConst>>, Spanned<RangeEnd>),
+
+    /// Placeholder for a pattern that wasn't syntactically well formed in some way.
+    Err(ErrorGuaranteed),
+}
+
 /// Syntax used to declare a trait object.
 #[derive(Clone, Copy, PartialEq, Encodable, Decodable, Debug, HashStable_Generic)]
 #[repr(u8)]

compiler/rustc_ast/src/mut_visit.rs

@@ -210,6 +210,10 @@ pub trait MutVisitor: Sized {
         walk_ty(self, t);
     }
 
+    fn visit_ty_pat(&mut self, t: &mut P<TyPat>) {
+        walk_ty_pat(self, t);
+    }
+
     fn visit_lifetime(&mut self, l: &mut Lifetime) {
         walk_lifetime(self, l);
     }
@@ -570,7 +574,7 @@ pub fn walk_ty<T: MutVisitor>(vis: &mut T, ty: &mut P<Ty>) {
         TyKind::Paren(ty) => vis.visit_ty(ty),
         TyKind::Pat(ty, pat) => {
             vis.visit_ty(ty);
-            vis.visit_pat(pat);
+            vis.visit_ty_pat(pat);
         }
         TyKind::Path(qself, path) => {
             vis.visit_qself(qself);
@@ -594,6 +598,20 @@ pub fn walk_ty<T: MutVisitor>(vis: &mut T, ty: &mut P<Ty>) {
     vis.visit_span(span);
 }
 
+pub fn walk_ty_pat<T: MutVisitor>(vis: &mut T, ty: &mut P<TyPat>) {
+    let TyPat { id, kind, span, tokens } = ty.deref_mut();
+    vis.visit_id(id);
+    match kind {
+        TyPatKind::Range(start, end, _include_end) => {
+            visit_opt(start, |c| vis.visit_anon_const(c));
+            visit_opt(end, |c| vis.visit_anon_const(c));
+        }
+        TyPatKind::Err(_) => {}
+    }
+    visit_lazy_tts(vis, tokens);
+    vis.visit_span(span);
+}
+
 fn walk_foreign_mod<T: MutVisitor>(vis: &mut T, foreign_mod: &mut ForeignMod) {
     let ForeignMod { extern_span: _, safety, abi: _, items } = foreign_mod;
     visit_safety(vis, safety);

compiler/rustc_ast/src/visit.rs

@@ -179,6 +179,9 @@ pub trait Visitor<'ast>: Sized {
     fn visit_ty(&mut self, t: &'ast Ty) -> Self::Result {
         walk_ty(self, t)
     }
+    fn visit_ty_pat(&mut self, t: &'ast TyPat) -> Self::Result {
+        walk_ty_pat(self, t)
+    }
     fn visit_generic_param(&mut self, param: &'ast GenericParam) -> Self::Result {
         walk_generic_param(self, param)
     }
@@ -534,7 +537,7 @@ pub fn walk_ty<'a, V: Visitor<'a>>(visitor: &mut V, typ: &'a Ty) -> V::Result {
         }
         TyKind::Pat(ty, pat) => {
             try_visit!(visitor.visit_ty(ty));
-            try_visit!(visitor.visit_pat(pat));
+            try_visit!(visitor.visit_ty_pat(pat));
         }
         TyKind::Array(ty, length) => {
             try_visit!(visitor.visit_ty(ty));
@@ -555,6 +558,18 @@ pub fn walk_ty<'a, V: Visitor<'a>>(visitor: &mut V, typ: &'a Ty) -> V::Result {
     V::Result::output()
 }
 
+pub fn walk_ty_pat<'a, V: Visitor<'a>>(visitor: &mut V, tp: &'a TyPat) -> V::Result {
+    let TyPat { id: _, kind, span: _, tokens: _ } = tp;
+    match kind {
+        TyPatKind::Range(start, end, _include_end) => {
+            visit_opt!(visitor, visit_anon_const, start);
+            visit_opt!(visitor, visit_anon_const, end);
+        }
+        TyPatKind::Err(_) => {}
+    }
+    V::Result::output()
+}
+
 fn walk_qself<'a, V: Visitor<'a>>(visitor: &mut V, qself: &'a Option<P<QSelf>>) -> V::Result {
     if let Some(qself) = qself {
         let QSelf { ty, path_span: _, position: _ } = &**qself;