Auto merge of rust-lang#134248 - oli-obk:patkind-path-removal, r=<try>

Merge `PatKind::Path` into `PatKind::Expr`

Follow-up to rust-lang#134228

We always had a duplication where `Path`s could be represented as `PatKind::Path` or `PatKind::Lit(ExprKind::Path)`. We had to handle both everywhere, and still do after rust-lang#134228, so I'm removing it now.

compiler/rustc_ast_lowering/src/expr.rs

@@ -1391,7 +1391,11 @@ impl<'hir> LoweringContext<'_, 'hir> {
                         None,
                     );
                     // Destructure like a unit struct.
-                    let unit_struct_pat = hir::PatKind::Path(qpath);
+                    let unit_struct_pat = hir::PatKind::Expr(self.arena.alloc(hir::PatExpr {
+                        kind: hir::PatExprKind::Path(qpath),
+                        hir_id: self.next_id(),
+                        span: self.lower_span(lhs.span),
+                    }));
                     return self.pat_without_dbm(lhs.span, unit_struct_pat);
                 }
             }

compiler/rustc_ast_lowering/src/pat.rs

@@ -69,7 +69,16 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
                             ImplTraitContext::Disallowed(ImplTraitPosition::Path),
                             None,
                         );
-                        break hir::PatKind::Path(qpath);
+                        let kind = hir::PatExprKind::Path(qpath);
+                        let span = self.lower_span(pattern.span);
+                        let expr = hir::PatExpr { hir_id: pat_hir_id, span, kind };
+                        let expr = self.arena.alloc(expr);
+                        return hir::Pat {
+                            hir_id: self.next_id(),
+                            kind: hir::PatKind::Expr(expr),
+                            span,
+                            default_binding_modes: true,
+                        };
                     }
                     PatKind::Struct(qself, path, fields, etc) => {
                         let qpath = self.lower_qpath(
@@ -304,16 +313,20 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
                 )
             }
             Some(res) => {
-                let hir_id = self.next_id();
                 let res = self.lower_res(res);
-                hir::PatKind::Path(hir::QPath::Resolved(
-                    None,
-                    self.arena.alloc(hir::Path {
-                        span: self.lower_span(ident.span),
-                        res,
-                        segments: arena_vec![self; hir::PathSegment::new(self.lower_ident(ident), hir_id, res)],
-                    }),
-            ))
+                let span = self.lower_span(ident.span);
+                hir::PatKind::Expr(self.arena.alloc(hir::PatExpr {
+                    kind: hir::PatExprKind::Path(hir::QPath::Resolved(
+                        None,
+                        self.arena.alloc(hir::Path {
+                            span,
+                            res,
+                            segments: arena_vec![self; hir::PathSegment::new(self.lower_ident(ident), self.next_id(), res)],
+                        }),
+                    )),
+                    hir_id: self.next_id(),
+                    span,
+                }))
             }
         }
     }

compiler/rustc_hir/src/hir.rs

@@ -1391,7 +1391,7 @@ impl<'hir> Pat<'hir> {
 
         use PatKind::*;
         match self.kind {
-            Wild | Never | Expr(_) | Range(..) | Binding(.., None) | Path(_) | Err(_) => true,
+            Wild | Never | Expr(_) | Range(..) | Binding(.., None) | Err(_) => true,
             Box(s) | Deref(s) | Ref(s, _) | Binding(.., Some(s)) | Guard(s, _) => s.walk_short_(it),
             Struct(_, fields, _) => fields.iter().all(|field| field.pat.walk_short_(it)),
             TupleStruct(_, s, _) | Tuple(s, _) | Or(s) => s.iter().all(|p| p.walk_short_(it)),
@@ -1418,7 +1418,7 @@ impl<'hir> Pat<'hir> {
 
         use PatKind::*;
         match self.kind {
-            Wild | Never | Expr(_) | Range(..) | Binding(.., None) | Path(_) | Err(_) => {}
+            Wild | Never | Expr(_) | Range(..) | Binding(.., None) | Err(_) => {}
             Box(s) | Deref(s) | Ref(s, _) | Binding(.., Some(s)) | Guard(s, _) => s.walk_(it),
             Struct(_, fields, _) => fields.iter().for_each(|field| field.pat.walk_(it)),
             TupleStruct(_, s, _) | Tuple(s, _) | Or(s) => s.iter().for_each(|p| p.walk_(it)),
@@ -1572,9 +1572,6 @@ pub enum PatKind<'hir> {
     /// A never pattern `!`.
     Never,
 
-    /// A path pattern for a unit struct/variant or a (maybe-associated) constant.
-    Path(QPath<'hir>),
-
     /// A tuple pattern (e.g., `(a, b)`).
     /// If the `..` pattern fragment is present, then `Option<usize>` denotes its position.
     /// `0 <= position <= subpats.len()`

compiler/rustc_hir/src/intravisit.rs

@@ -668,9 +668,6 @@ pub fn walk_pat<'v, V: Visitor<'v>>(visitor: &mut V, pattern: &'v Pat<'v>) -> V:
             try_visit!(visitor.visit_qpath(qpath, pattern.hir_id, pattern.span));
             walk_list!(visitor, visit_pat, children);
         }
-        PatKind::Path(ref qpath) => {
-            try_visit!(visitor.visit_qpath(qpath, pattern.hir_id, pattern.span));
-        }
         PatKind::Struct(ref qpath, fields, _) => {
             try_visit!(visitor.visit_qpath(qpath, pattern.hir_id, pattern.span));
             walk_list!(visitor, visit_pat_field, fields);

compiler/rustc_hir/src/pat_util.rs

@@ -105,7 +105,10 @@ impl hir::Pat<'_> {
         let mut variants = vec![];
         self.walk(|p| match &p.kind {
             PatKind::Or(_) => false,
-            PatKind::Path(hir::QPath::Resolved(_, path))
+            PatKind::Expr(hir::PatExpr {
+                kind: hir::PatExprKind::Path(hir::QPath::Resolved(_, path)),
+                ..
+            })
             | PatKind::TupleStruct(hir::QPath::Resolved(_, path), ..)
             | PatKind::Struct(hir::QPath::Resolved(_, path), ..) => {
                 if let Res::Def(DefKind::Variant | DefKind::Ctor(CtorOf::Variant, ..), id) =

compiler/rustc_hir_analysis/src/check/region.rs

@@ -703,7 +703,6 @@ fn resolve_local<'tcx>(
             | PatKind::Binding(hir::BindingMode(hir::ByRef::No, _), ..)
             | PatKind::Wild
             | PatKind::Never
-            | PatKind::Path(_)
             | PatKind::Expr(_)
             | PatKind::Range(_, _, _)
             | PatKind::Err(_) => false,

compiler/rustc_hir_analysis/src/hir_ty_lowering/lint.rs

@@ -38,8 +38,8 @@ impl<'tcx> dyn HirTyLowerer<'tcx> + '_ {
                 kind: hir::ExprKind::Path(hir::QPath::TypeRelative(qself, _)),
                 ..
             })
-            | hir::Node::Pat(hir::Pat {
-                kind: hir::PatKind::Path(hir::QPath::TypeRelative(qself, _)),
+            | hir::Node::PatExpr(hir::PatExpr {
+                kind: hir::PatExprKind::Path(hir::QPath::TypeRelative(qself, _)),
                 ..
             }) if qself.hir_id == self_ty.hir_id => true,
             _ => false,

compiler/rustc_hir_pretty/src/lib.rs

@@ -1905,9 +1905,6 @@ impl<'a> State<'a> {
                 }
                 self.pclose();
             }
-            PatKind::Path(ref qpath) => {
-                self.print_qpath(qpath, true);
-            }
             PatKind::Struct(ref qpath, fields, etc) => {
                 self.print_qpath(qpath, true);
                 self.nbsp();

compiler/rustc_hir_typeck/src/expr.rs

@@ -480,7 +480,6 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
             hir::PatKind::Binding(_, _, _, _)
             | hir::PatKind::Struct(_, _, _)
             | hir::PatKind::TupleStruct(_, _, _)
-            | hir::PatKind::Path(_)
             | hir::PatKind::Tuple(_, _)
             | hir::PatKind::Box(_)
             | hir::PatKind::Ref(_, _)

compiler/rustc_hir_typeck/src/expr_use_visitor.rs

@@ -11,10 +11,9 @@ use hir::def::DefKind;
 use hir::pat_util::EnumerateAndAdjustIterator as _;
 use rustc_abi::{FIRST_VARIANT, FieldIdx, VariantIdx};
 use rustc_data_structures::fx::FxIndexMap;
-use rustc_hir as hir;
 use rustc_hir::def::{CtorOf, Res};
 use rustc_hir::def_id::LocalDefId;
-use rustc_hir::{HirId, PatKind};
+use rustc_hir::{self as hir, HirId, PatExpr, PatExprKind, PatKind};
 use rustc_lint::LateContext;
 use rustc_middle::hir::place::ProjectionKind;
 // Export these here so that Clippy can use them.
@@ -564,11 +563,11 @@ impl<'tcx, Cx: TypeInformationCtxt<'tcx>, D: Delegate<'tcx>> ExprUseVisitor<'tcx
                         // FIXME(never_patterns): does this do what I expect?
                         needs_to_be_read = true;
                     }
-                    PatKind::Path(qpath) => {
+                    PatKind::Expr(PatExpr { kind: PatExprKind::Path(qpath), hir_id, span }) => {
                         // A `Path` pattern is just a name like `Foo`. This is either a
                         // named constant or else it refers to an ADT variant
 
-                        let res = self.cx.typeck_results().qpath_res(qpath, pat.hir_id);
+                        let res = self.cx.typeck_results().qpath_res(qpath, *hir_id);
                         match res {
                             Res::Def(DefKind::Const, _) | Res::Def(DefKind::AssocConst, _) => {
                                 // Named constants have to be equated with the value
@@ -581,7 +580,7 @@ impl<'tcx, Cx: TypeInformationCtxt<'tcx>, D: Delegate<'tcx>> ExprUseVisitor<'tcx
                                 // Otherwise, this is a struct/enum variant, and so it's
                                 // only a read if we need to read the discriminant.
                                 needs_to_be_read |=
-                                    self.is_multivariant_adt(place.place.ty(), pat.span);
+                                    self.is_multivariant_adt(place.place.ty(), *span);
                             }
                         }
                     }
@@ -1801,8 +1800,7 @@ impl<'tcx, Cx: TypeInformationCtxt<'tcx>, D: Delegate<'tcx>> ExprUseVisitor<'tcx
                 }
             }
 
-            PatKind::Path(_)
-            | PatKind::Binding(.., None)
+            PatKind::Binding(.., None)
             | PatKind::Expr(..)
             | PatKind::Range(..)
             | PatKind::Never

compiler/rustc_hir_typeck/src/fn_ctxt/suggestions.rs

@@ -5,12 +5,12 @@ use hir::def_id::LocalDefId;
 use rustc_ast::util::parser::ExprPrecedence;
 use rustc_data_structures::packed::Pu128;
 use rustc_errors::{Applicability, Diag, MultiSpan};
-use rustc_hir as hir;
 use rustc_hir::def::{CtorKind, CtorOf, DefKind, Res};
 use rustc_hir::lang_items::LangItem;
 use rustc_hir::{
-    Arm, CoroutineDesugaring, CoroutineKind, CoroutineSource, Expr, ExprKind, GenericBound, HirId,
-    Node, Path, QPath, Stmt, StmtKind, TyKind, WherePredicateKind, expr_needs_parens,
+    self as hir, Arm, CoroutineDesugaring, CoroutineKind, CoroutineSource, Expr, ExprKind,
+    GenericBound, HirId, Node, PatExpr, PatExprKind, Path, QPath, Stmt, StmtKind, TyKind,
+    WherePredicateKind, expr_needs_parens,
 };
 use rustc_hir_analysis::collect::suggest_impl_trait;
 use rustc_hir_analysis::hir_ty_lowering::HirTyLowerer;
@@ -1419,8 +1419,8 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
         // since the user probably just misunderstood how `let else`
         // and `&&` work together.
         if let Some((_, hir::Node::LetStmt(local))) = cond_parent
-            && let hir::PatKind::Path(qpath) | hir::PatKind::TupleStruct(qpath, _, _) =
-                &local.pat.kind
+            && let hir::PatKind::Expr(PatExpr { kind: PatExprKind::Path(qpath), .. })
+            | hir::PatKind::TupleStruct(qpath, _, _) = &local.pat.kind
             && let hir::QPath::Resolved(None, path) = qpath
             && let Some(did) = path
                 .res

compiler/rustc_hir_typeck/src/method/suggest.rs

@@ -177,8 +177,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
             })
             | hir::Node::Pat(&hir::Pat {
                 kind:
-                    hir::PatKind::Path(QPath::TypeRelative(rcvr, segment))
-                    | hir::PatKind::Struct(QPath::TypeRelative(rcvr, segment), ..)
+                    hir::PatKind::Struct(QPath::TypeRelative(rcvr, segment), ..)
                     | hir::PatKind::TupleStruct(QPath::TypeRelative(rcvr, segment), ..),
                 span,
                 ..

compiler/rustc_hir_typeck/src/pat.rs

@@ -11,8 +11,8 @@ use rustc_errors::{
 use rustc_hir::def::{CtorKind, DefKind, Res};
 use rustc_hir::pat_util::EnumerateAndAdjustIterator;
 use rustc_hir::{
-    self as hir, BindingMode, ByRef, ExprKind, HirId, LangItem, Mutability, Pat, PatKind,
-    expr_needs_parens,
+    self as hir, BindingMode, ByRef, ExprKind, HirId, LangItem, Mutability, Pat, PatExpr,
+    PatExprKind, PatKind, expr_needs_parens,
 };
 use rustc_infer::infer;
 use rustc_middle::traits::PatternOriginExpr;
@@ -312,9 +312,9 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
     fn check_pat(&self, pat: &'tcx Pat<'tcx>, expected: Ty<'tcx>, pat_info: PatInfo<'_, 'tcx>) {
         let PatInfo { binding_mode, max_ref_mutbl, top_info: ti, current_depth, .. } = pat_info;
 
-        let path_res = match &pat.kind {
-            PatKind::Path(qpath) => {
-                Some(self.resolve_ty_and_res_fully_qualified_call(qpath, pat.hir_id, pat.span))
+        let path_res = match pat.kind {
+            PatKind::Expr(PatExpr { kind: PatExprKind::Path(ref qpath), hir_id, span }) => {
+                Some(self.resolve_ty_and_res_fully_qualified_call(qpath, *hir_id, *span))
             }
             _ => None,
         };
@@ -333,6 +333,12 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
             PatKind::Wild | PatKind::Err(_) => expected,
             // We allow any type here; we ensure that the type is uninhabited during match checking.
             PatKind::Never => expected,
+            PatKind::Expr(PatExpr { kind: PatExprKind::Path(ref qpath), hir_id, span }) => {
+                let ty =
+                    self.check_pat_path(*hir_id, *span, qpath, path_res.unwrap(), expected, ti);
+                self.write_ty(*hir_id, ty);
+                ty
+            }
             PatKind::Expr(lt) => self.check_pat_lit(pat.span, lt, expected, ti),
             PatKind::Range(lhs, rhs, _) => self.check_pat_range(pat.span, lhs, rhs, expected, ti),
             PatKind::Binding(ba, var_id, ident, sub) => {
@@ -341,9 +347,6 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
             PatKind::TupleStruct(ref qpath, subpats, ddpos) => {
                 self.check_pat_tuple_struct(pat, qpath, subpats, ddpos, expected, pat_info)
             }
-            PatKind::Path(ref qpath) => {
-                self.check_pat_path(pat.hir_id, pat.span, qpath, path_res.unwrap(), expected, ti)
-            }
             PatKind::Struct(ref qpath, fields, has_rest_pat) => {
                 self.check_pat_struct(pat, qpath, fields, has_rest_pat, expected, pat_info)
             }
@@ -456,16 +459,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
             | PatKind::Slice(..) => AdjustMode::Peel,
             // A never pattern behaves somewhat like a literal or unit variant.
             PatKind::Never => AdjustMode::Peel,
-            // String and byte-string literals result in types `&str` and `&[u8]` respectively.
-            // All other literals result in non-reference types.
-            // As a result, we allow `if let 0 = &&0 {}` but not `if let "foo" = &&"foo" {}`.
-            //
-            // Call `resolve_vars_if_possible` here for inline const blocks.
-            PatKind::Expr(lt) => match self.resolve_vars_if_possible(self.check_pat_expr_unadjusted(lt)).kind() {
-                ty::Ref(..) => AdjustMode::Pass,
-                _ => AdjustMode::Peel,
-            },
-            PatKind::Path(_) => match opt_path_res.unwrap() {
+            PatKind::Expr(PatExpr { kind: PatExprKind::Path(_), .. }) => match opt_path_res.unwrap() {
                 // These constants can be of a reference type, e.g. `const X: &u8 = &0;`.
                 // Peeling the reference types too early will cause type checking failures.
                 // Although it would be possible to *also* peel the types of the constants too.
@@ -476,6 +470,17 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                 // a reference type wherefore peeling doesn't give up any expressiveness.
                 _ => AdjustMode::Peel,
             },
+
+            // String and byte-string literals result in types `&str` and `&[u8]` respectively.
+            // All other literals result in non-reference types.
+            // As a result, we allow `if let 0 = &&0 {}` but not `if let "foo" = &&"foo" {}`.
+            //
+            // Call `resolve_vars_if_possible` here for inline const blocks.
+            PatKind::Expr(lt) => match self.resolve_vars_if_possible(self.check_pat_expr_unadjusted(lt)).kind() {
+                ty::Ref(..) => AdjustMode::Pass,
+                _ => AdjustMode::Peel,
+            },
+
             // Ref patterns are complicated, we handle them in `check_pat_ref`.
             PatKind::Ref(..) => AdjustMode::Pass,
             // A `_` pattern works with any expected type, so there's no need to do anything.
@@ -1001,7 +1006,6 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                         PatKind::Wild
                         | PatKind::Never
                         | PatKind::Binding(..)
-                        | PatKind::Path(..)
                         | PatKind::Box(..)
                         | PatKind::Deref(_)
                         | PatKind::Ref(..)

compiler/rustc_lint/src/internal.rs

@@ -5,8 +5,8 @@ use rustc_ast as ast;
 use rustc_hir::def::Res;
 use rustc_hir::def_id::DefId;
 use rustc_hir::{
-    BinOp, BinOpKind, Expr, ExprKind, GenericArg, HirId, Impl, Item, ItemKind, Node, Pat, PatKind,
-    Path, PathSegment, QPath, Ty, TyKind,
+    BinOp, BinOpKind, Expr, ExprKind, GenericArg, HirId, Impl, Item, ItemKind, Node, Pat, PatExpr,
+    PatExprKind, PatKind, Path, PathSegment, QPath, Ty, TyKind,
 };
 use rustc_middle::ty::{self, GenericArgsRef, Ty as MiddleTy};
 use rustc_session::{declare_lint_pass, declare_tool_lint};
@@ -164,11 +164,9 @@ impl<'tcx> LateLintPass<'tcx> for TyTyKind {
             TyKind::Path(QPath::Resolved(_, path)) => {
                 if lint_ty_kind_usage(cx, &path.res) {
                     let span = match cx.tcx.parent_hir_node(ty.hir_id) {
-                        Node::Pat(Pat {
-                            kind:
-                                PatKind::Path(qpath)
-                                | PatKind::TupleStruct(qpath, ..)
-                                | PatKind::Struct(qpath, ..),
+                        Node::PatExpr(PatExpr { kind: PatExprKind::Path(qpath), .. })
+                        | Node::Pat(Pat {
+                            kind: PatKind::TupleStruct(qpath, ..) | PatKind::Struct(qpath, ..),
                             ..
                         })
                         | Node::Expr(

compiler/rustc_lint/src/nonstandard_style.rs

@@ -1,7 +1,7 @@
 use rustc_abi::ExternAbi;
 use rustc_hir::def::{DefKind, Res};
 use rustc_hir::intravisit::FnKind;
-use rustc_hir::{AttrArgs, AttrItem, AttrKind, GenericParamKind, PatKind};
+use rustc_hir::{AttrArgs, AttrItem, AttrKind, GenericParamKind, PatExprKind, PatKind};
 use rustc_middle::ty;
 use rustc_session::config::CrateType;
 use rustc_session::{declare_lint, declare_lint_pass};
@@ -527,7 +527,11 @@ impl<'tcx> LateLintPass<'tcx> for NonUpperCaseGlobals {
 
     fn check_pat(&mut self, cx: &LateContext<'_>, p: &hir::Pat<'_>) {
         // Lint for constants that look like binding identifiers (#7526)
-        if let PatKind::Path(hir::QPath::Resolved(None, path)) = p.kind {
+        if let PatKind::Expr(hir::PatExpr {
+            kind: PatExprKind::Path(hir::QPath::Resolved(None, path)),
+            ..
+        }) = p.kind
+        {
             if let Res::Def(DefKind::Const, _) = path.res {
                 if let [segment] = path.segments {
                     NonUpperCaseGlobals::check_upper_case(

compiler/rustc_mir_build/src/thir/pattern/mod.rs

@@ -332,10 +332,6 @@ impl<'a, 'tcx> PatCtxt<'a, 'tcx> {
                     .unwrap_or_else(PatKind::Error)
             }
 
-            hir::PatKind::Path(ref qpath) => {
-                return self.lower_path(qpath, pat.hir_id, pat.span);
-            }
-
             hir::PatKind::Deref(subpattern) => {
                 let mutable = self.typeck_results.pat_has_ref_mut_binding(subpattern);
                 let mutability = if mutable { hir::Mutability::Mut } else { hir::Mutability::Not };