Rollup merge of #136646 - oli-obk:pattern-types-ast, r=BoxyUwU

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

This simplifies ast lowering significantly with little cost to the pattern types parser.

Also fixes any problems we've had with generic args (well, pushes any problems onto the `generic_const_exprs` feature gate)

follow-up to https://github.com/rust-lang/rust/pull/136284#discussion_r1939292367

r? ``@BoxyUwU``

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;

compiler/rustc_ast_lowering/src/pat.rs

@@ -4,10 +4,10 @@ use rustc_ast::ptr::P;
 use rustc_ast::*;
 use rustc_data_structures::stack::ensure_sufficient_stack;
 use rustc_hir as hir;
-use rustc_hir::def::{DefKind, Res};
+use rustc_hir::def::Res;
 use rustc_middle::span_bug;
 use rustc_span::source_map::{Spanned, respan};
-use rustc_span::{Ident, Span, kw};
+use rustc_span::{Ident, Span};
 
 use super::errors::{
     ArbitraryExpressionInPattern, ExtraDoubleDot, MisplacedDoubleDot, SubTupleBinding,
@@ -430,78 +430,20 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
         self.arena.alloc(hir::PatExpr { hir_id: self.lower_node_id(expr.id), span, kind })
     }
 
-    pub(crate) fn lower_ty_pat(&mut self, pattern: &Pat) -> &'hir hir::TyPat<'hir> {
+    pub(crate) fn lower_ty_pat(&mut self, pattern: &TyPat) -> &'hir hir::TyPat<'hir> {
         self.arena.alloc(self.lower_ty_pat_mut(pattern))
     }
 
-    fn lower_ty_pat_mut(&mut self, mut pattern: &Pat) -> hir::TyPat<'hir> {
+    fn lower_ty_pat_mut(&mut self, pattern: &TyPat) -> hir::TyPat<'hir> {
         // loop here to avoid recursion
         let pat_hir_id = self.lower_node_id(pattern.id);
-        let node = loop {
-            match &pattern.kind {
-                PatKind::Range(e1, e2, Spanned { node: end, .. }) => {
-                    // FIXME(pattern_types): remove this closure and call `lower_const_arg` instead.
-                    // That requires first modifying the AST to have const args here.
-                    let mut lower_expr = |e: &Expr| -> &_ {
-                        if let ExprKind::Path(None, path) = &e.kind
-                            && let Some(res) = self
-                                .resolver
-                                .get_partial_res(e.id)
-                                .and_then(|partial_res| partial_res.full_res())
-                        {
-                            self.lower_const_path_to_const_arg(path, res, e.id, e.span)
-                        } else {
-                            let node_id = self.next_node_id();
-                            let def_id = self.create_def(
-                                self.current_hir_id_owner.def_id,
-                                node_id,
-                                kw::Empty,
-                                DefKind::AnonConst,
-                                e.span,
-                            );
-                            let hir_id = self.lower_node_id(node_id);
-                            let ac = self.arena.alloc(hir::AnonConst {
-                                def_id,
-                                hir_id,
-                                body: self.lower_const_body(pattern.span, Some(e)),
-                                span: self.lower_span(pattern.span),
-                            });
-                            self.arena.alloc(hir::ConstArg {
-                                hir_id: self.next_id(),
-                                kind: hir::ConstArgKind::Anon(ac),
-                            })
-                        }
-                    };
-                    break hir::TyPatKind::Range(
-                        e1.as_deref().map(|e| lower_expr(e)),
-                        e2.as_deref().map(|e| lower_expr(e)),
-                        self.lower_range_end(end, e2.is_some()),
-                    );
-                }
-                // return inner to be processed in next loop
-                PatKind::Paren(inner) => pattern = inner,
-                PatKind::MacCall(_) => panic!("{:?} shouldn't exist here", pattern.span),
-                PatKind::Err(guar) => break hir::TyPatKind::Err(*guar),
-                PatKind::Deref(..)
-                | PatKind::Box(..)
-                | PatKind::Or(..)
-                | PatKind::Struct(..)
-                | PatKind::TupleStruct(..)
-                | PatKind::Tuple(..)
-                | PatKind::Ref(..)
-                | PatKind::Expr(..)
-                | PatKind::Guard(..)
-                | PatKind::Slice(_)
-                | PatKind::Ident(..)
-                | PatKind::Path(..)
-                | PatKind::Wild
-                | PatKind::Never
-                | PatKind::Rest => {
-                    break hir::TyPatKind::Err(
-                        self.dcx().span_err(pattern.span, "pattern not supported in pattern types"),
-                    );
-                }
-            }
+        let node = match &pattern.kind {
+            TyPatKind::Range(e1, e2, Spanned { node: end, .. }) => hir::TyPatKind::Range(
+                e1.as_deref().map(|e| self.lower_anon_const_to_const_arg(e)),
+                e2.as_deref().map(|e| self.lower_anon_const_to_const_arg(e)),
+                self.lower_range_end(end, e2.is_some()),
+            ),
+            TyPatKind::Err(guar) => hir::TyPatKind::Err(*guar),
         };
 
         hir::TyPat { hir_id: pat_hir_id, kind: node, span: self.lower_span(pattern.span) }

compiler/rustc_ast_pretty/src/pprust/state.rs

@@ -1148,6 +1148,28 @@ impl<'a> State<'a> {
         }
     }
 
+    pub fn print_ty_pat(&mut self, pat: &ast::TyPat) {
+        match &pat.kind {
+            rustc_ast::TyPatKind::Range(start, end, include_end) => {
+                if let Some(start) = start {
+                    self.print_expr_anon_const(start, &[]);
+                }
+                self.word("..");
+                if let Some(end) = end {
+                    if let RangeEnd::Included(_) = include_end.node {
+                        self.word("=");
+                    }
+                    self.print_expr_anon_const(end, &[]);
+                }
+            }
+            rustc_ast::TyPatKind::Err(_) => {
+                self.popen();
+                self.word("/*ERROR*/");
+                self.pclose();
+            }
+        }
+    }
+
     pub fn print_type(&mut self, ty: &ast::Ty) {
         self.maybe_print_comment(ty.span.lo());
         self.ibox(0);
@@ -1252,7 +1274,7 @@ impl<'a> State<'a> {
             ast::TyKind::Pat(ty, pat) => {
                 self.print_type(ty);
                 self.word(" is ");
-                self.print_pat(pat);
+                self.print_ty_pat(pat);
             }
         }
         self.end();

compiler/rustc_builtin_macros/src/pattern_type.rs

@@ -1,6 +1,6 @@
 use rustc_ast::ptr::P;
 use rustc_ast::tokenstream::TokenStream;
-use rustc_ast::{Pat, Ty, ast};
+use rustc_ast::{AnonConst, DUMMY_NODE_ID, Ty, TyPat, TyPatKind, ast};
 use rustc_errors::PResult;
 use rustc_expand::base::{self, DummyResult, ExpandResult, ExtCtxt, MacroExpanderResult};
 use rustc_parse::exp;
@@ -21,12 +21,24 @@ pub(crate) fn expand<'cx>(
     ExpandResult::Ready(base::MacEager::ty(cx.ty(sp, ast::TyKind::Pat(ty, pat))))
 }
 
-fn parse_pat_ty<'a>(cx: &mut ExtCtxt<'a>, stream: TokenStream) -> PResult<'a, (P<Ty>, P<Pat>)> {
+fn parse_pat_ty<'a>(cx: &mut ExtCtxt<'a>, stream: TokenStream) -> PResult<'a, (P<Ty>, P<TyPat>)> {
     let mut parser = cx.new_parser_from_tts(stream);
 
     let ty = parser.parse_ty()?;
     parser.expect_keyword(exp!(Is))?;
-    let pat = parser.parse_pat_no_top_alt(None, None)?;
+    let pat = parser.parse_pat_no_top_alt(None, None)?.into_inner();
+
+    let kind = match pat.kind {
+        ast::PatKind::Range(start, end, include_end) => TyPatKind::Range(
+            start.map(|value| P(AnonConst { id: DUMMY_NODE_ID, value })),
+            end.map(|value| P(AnonConst { id: DUMMY_NODE_ID, value })),
+            include_end,
+        ),
+        ast::PatKind::Err(guar) => TyPatKind::Err(guar),
+        _ => TyPatKind::Err(cx.dcx().span_err(pat.span, "pattern not supported in pattern types")),
+    };
+
+    let pat = P(TyPat { id: pat.id, kind, span: pat.span, tokens: pat.tokens });
 
     Ok((ty, pat))
 }

compiler/rustc_resolve/src/late.rs

@@ -923,6 +923,21 @@ impl<'ra: 'ast, 'ast, 'tcx> Visitor<'ast> for LateResolutionVisitor<'_, 'ast, 'r
         self.diag_metadata.current_trait_object = prev;
         self.diag_metadata.current_type_path = prev_ty;
     }
+
+    fn visit_ty_pat(&mut self, t: &'ast TyPat) -> Self::Result {
+        match &t.kind {
+            TyPatKind::Range(start, end, _) => {
+                if let Some(start) = start {
+                    self.resolve_anon_const(start, AnonConstKind::ConstArg(IsRepeatExpr::No));
+                }
+                if let Some(end) = end {
+                    self.resolve_anon_const(end, AnonConstKind::ConstArg(IsRepeatExpr::No));
+                }
+            }
+            TyPatKind::Err(_) => {}
+        }
+    }
+
     fn visit_poly_trait_ref(&mut self, tref: &'ast PolyTraitRef) {
         let span = tref.span.shrink_to_lo().to(tref.trait_ref.path.span.shrink_to_lo());
         self.with_generic_param_rib(