Exhaustively handle expressions in patterns

Author: oli-obk

Diff for: compiler/rustc_ast_lowering/src/expr.rs

@@ -102,17 +102,7 @@ impl<'hir> LoweringContext<'_, 'hir> {
 
             let kind = match &e.kind {
                 ExprKind::Array(exprs) => hir::ExprKind::Array(self.lower_exprs(exprs)),
-                ExprKind::ConstBlock(c) => {
-                    let c = self.with_new_scopes(c.value.span, |this| {
-                        let def_id = this.local_def_id(c.id);
-                        hir::ConstBlock {
-                            def_id,
-                            hir_id: this.lower_node_id(c.id),
-                            body: this.lower_const_body(c.value.span, Some(&c.value)),
-                        }
-                    });
-                    hir::ExprKind::ConstBlock(c)
-                }
+                ExprKind::ConstBlock(c) => hir::ExprKind::ConstBlock(self.lower_const_block(c)),
                 ExprKind::Repeat(expr, count) => {
                     let expr = self.lower_expr(expr);
                     let count = self.lower_array_length_to_const_arg(count);
@@ -153,18 +143,7 @@ impl<'hir> LoweringContext<'_, 'hir> {
                     let ohs = self.lower_expr(ohs);
                     hir::ExprKind::Unary(op, ohs)
                 }
-                ExprKind::Lit(token_lit) => {
-                    let lit_kind = match LitKind::from_token_lit(*token_lit) {
-                        Ok(lit_kind) => lit_kind,
-                        Err(err) => {
-                            let guar =
-                                report_lit_error(&self.tcx.sess.psess, err, *token_lit, e.span);
-                            LitKind::Err(guar)
-                        }
-                    };
-                    let lit = self.arena.alloc(respan(self.lower_span(e.span), lit_kind));
-                    hir::ExprKind::Lit(lit)
-                }
+                ExprKind::Lit(token_lit) => hir::ExprKind::Lit(self.lower_lit(token_lit, e.span)),
                 ExprKind::IncludedBytes(bytes) => {
                     let lit = self.arena.alloc(respan(
                         self.lower_span(e.span),
@@ -403,6 +382,32 @@ impl<'hir> LoweringContext<'_, 'hir> {
         })
     }
 
+    pub(crate) fn lower_const_block(&mut self, c: &AnonConst) -> hir::ConstBlock {
+        self.with_new_scopes(c.value.span, |this| {
+            let def_id = this.local_def_id(c.id);
+            hir::ConstBlock {
+                def_id,
+                hir_id: this.lower_node_id(c.id),
+                body: this.lower_const_body(c.value.span, Some(&c.value)),
+            }
+        })
+    }
+
+    pub(crate) fn lower_lit(
+        &mut self,
+        token_lit: &token::Lit,
+        span: Span,
+    ) -> &'hir Spanned<LitKind> {
+        let lit_kind = match LitKind::from_token_lit(*token_lit) {
+            Ok(lit_kind) => lit_kind,
+            Err(err) => {
+                let guar = report_lit_error(&self.tcx.sess.psess, err, *token_lit, span);
+                LitKind::Err(guar)
+            }
+        };
+        self.arena.alloc(respan(self.lower_span(span), lit_kind))
+    }
+
     fn lower_unop(&mut self, u: UnOp) -> hir::UnOp {
         match u {
             UnOp::Deref => hir::UnOp::Deref,

Diff for: compiler/rustc_ast_lowering/src/index.rs

@@ -209,6 +209,14 @@ impl<'a, 'hir> Visitor<'hir> for NodeCollector<'a, 'hir> {
         });
     }
 
+    fn visit_pat_expr(&mut self, expr: &'hir PatExpr<'hir>) {
+        self.insert(expr.span, expr.hir_id, Node::PatExpr(expr));
+
+        self.with_parent(expr.hir_id, |this| {
+            intravisit::walk_pat_expr(this, expr);
+        });
+    }
+
     fn visit_pat_field(&mut self, field: &'hir PatField<'hir>) {
         self.insert(field.span, field.hir_id, Node::PatField(field));
         self.with_parent(field.hir_id, |this| {

Diff for: compiler/rustc_ast_lowering/src/lib.rs

@@ -35,6 +35,7 @@
 #![doc(rust_logo)]
 #![feature(assert_matches)]
 #![feature(box_patterns)]
+#![feature(if_let_guard)]
 #![feature(let_chains)]
 #![feature(rustdoc_internals)]
 #![warn(unreachable_pub)]

Diff for: compiler/rustc_ast_lowering/src/pat.rs

@@ -1,9 +1,12 @@
+use std::sync::Arc;
+
 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::Res;
-use rustc_span::source_map::Spanned;
+use rustc_middle::span_bug;
+use rustc_span::source_map::{Spanned, respan};
 use rustc_span::{Ident, Span};
 
 use super::errors::{
@@ -366,24 +369,46 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
     // }
     // m!(S);
     // ```
-    fn lower_expr_within_pat(&mut self, expr: &Expr, allow_paths: bool) -> &'hir hir::Expr<'hir> {
-        match &expr.kind {
-            ExprKind::Lit(..)
-            | ExprKind::ConstBlock(..)
-            | ExprKind::IncludedBytes(..)
-            | ExprKind::Err(_)
-            | ExprKind::Dummy => {}
-            ExprKind::Path(..) if allow_paths => {}
-            ExprKind::Unary(UnOp::Neg, inner) if matches!(inner.kind, ExprKind::Lit(_)) => {}
+    fn lower_expr_within_pat(&mut self, expr: &Expr, allow_paths: bool) -> &'hir hir::PatExpr<'hir> {
+        let err = |guar| hir::PatExprKind::Lit {
+            lit: self.arena.alloc(respan(self.lower_span(expr.span), LitKind::Err(guar))),
+            negated: false,
+        };
+        let kind = match &expr.kind {
+            ExprKind::Lit(lit) => {
+                hir::PatExprKind::Lit { lit: self.lower_lit(lit, expr.span), negated: false }
+            }
+            ExprKind::ConstBlock(c) => hir::PatExprKind::ConstBlock(self.lower_const_block(c)),
+            ExprKind::IncludedBytes(bytes) => hir::PatExprKind::Lit {
+                lit: self.arena.alloc(respan(
+                    self.lower_span(expr.span),
+                    LitKind::ByteStr(Arc::clone(bytes), StrStyle::Cooked),
+                )),
+                negated: false,
+            },
+            ExprKind::Err(guar) => err(*guar),
+            ExprKind::Dummy => span_bug!(expr.span, "lowered ExprKind::Dummy"),
+            ExprKind::Path(qself, path) if allow_paths => hir::PatExprKind::Path(self.lower_qpath(
+                expr.id,
+                qself,
+                path,
+                ParamMode::Optional,
+                AllowReturnTypeNotation::No,
+                ImplTraitContext::Disallowed(ImplTraitPosition::Path),
+                None,
+            )),
+            ExprKind::Unary(UnOp::Neg, inner) if let ExprKind::Lit(lit) = &inner.kind => {
+                hir::PatExprKind::Lit { lit: self.lower_lit(lit, expr.span), negated: true }
+            }
             _ => {
                 let pattern_from_macro = expr.is_approximately_pattern();
                 let guar = self.dcx().emit_err(ArbitraryExpressionInPattern {
                     span: expr.span,
                     pattern_from_macro_note: pattern_from_macro,
                 });
-                return self.arena.alloc(self.expr_err(expr.span, guar));
+                err(guar)
             }
-        }
-        self.lower_expr(expr)
+        };
+        self.arena.alloc(hir::PatExpr { hir_id: self.lower_node_id(expr.id), span: expr.span, kind })
     }
 }

Diff for: compiler/rustc_hir/src/hir.rs

@@ -1519,6 +1519,26 @@ impl fmt::Debug for DotDotPos {
     }
 }
 
+#[derive(Debug, Clone, Copy, HashStable_Generic)]
+pub struct PatExpr<'hir> {
+    pub hir_id: HirId,
+    pub span: Span,
+    pub kind: PatExprKind<'hir>,
+}
+
+#[derive(Debug, Clone, Copy, HashStable_Generic)]
+pub enum PatExprKind<'hir> {
+    Lit {
+        lit: &'hir Lit,
+        // FIXME: move this into `Lit` and handle negated literal expressions
+        // once instead of matching on unop neg expressions everywhere.
+        negated: bool,
+    },
+    ConstBlock(ConstBlock),
+    /// A path pattern for a unit struct/variant or a (maybe-associated) constant.
+    Path(QPath<'hir>),
+}
+
 #[derive(Debug, Clone, Copy, HashStable_Generic)]
 pub enum PatKind<'hir> {
     /// Represents a wildcard pattern (i.e., `_`).
@@ -1564,10 +1584,10 @@ pub enum PatKind<'hir> {
     Ref(&'hir Pat<'hir>, Mutability),
 
     /// A literal.
-    Lit(&'hir Expr<'hir>),
+    Lit(&'hir PatExpr<'hir>),
 
     /// A range pattern (e.g., `1..=2` or `1..2`).
-    Range(Option<&'hir Expr<'hir>>, Option<&'hir Expr<'hir>>, RangeEnd),
+    Range(Option<&'hir PatExpr<'hir>>, Option<&'hir PatExpr<'hir>>, RangeEnd),
 
     /// A slice pattern, `[before_0, ..., before_n, (slice, after_0, ..., after_n)?]`.
     ///
@@ -4141,6 +4161,10 @@ pub enum Node<'hir> {
     OpaqueTy(&'hir OpaqueTy<'hir>),
     Pat(&'hir Pat<'hir>),
     PatField(&'hir PatField<'hir>),
+    /// Needed as its own node with its own HirId for tracking
+    /// the unadjusted type of literals within patterns
+    /// (e.g. byte str literals not being of slice type).
+    PatExpr(&'hir PatExpr<'hir>),
     Arm(&'hir Arm<'hir>),
     Block(&'hir Block<'hir>),
     LetStmt(&'hir LetStmt<'hir>),
@@ -4197,6 +4221,7 @@ impl<'hir> Node<'hir> {
             | Node::Block(..)
             | Node::Ctor(..)
             | Node::Pat(..)
+            | Node::PatExpr(..)
             | Node::Arm(..)
             | Node::LetStmt(..)
             | Node::Crate(..)

Diff for: compiler/rustc_hir/src/intravisit.rs

@@ -342,6 +342,9 @@ pub trait Visitor<'v>: Sized {
     fn visit_pat_field(&mut self, f: &'v PatField<'v>) -> Self::Result {
         walk_pat_field(self, f)
     }
+    fn visit_pat_expr(&mut self, lit: &'v PatExpr<'v>) -> Self::Result {
+        walk_pat_expr(self, lit)
+    }
     fn visit_anon_const(&mut self, c: &'v AnonConst) -> Self::Result {
         walk_anon_const(self, c)
     }
@@ -685,10 +688,10 @@ pub fn walk_pat<'v, V: Visitor<'v>>(visitor: &mut V, pattern: &'v Pat<'v>) -> V:
             try_visit!(visitor.visit_ident(ident));
             visit_opt!(visitor, visit_pat, optional_subpattern);
         }
-        PatKind::Lit(ref expression) => try_visit!(visitor.visit_expr(expression)),
+        PatKind::Lit(lit) => try_visit!(visitor.visit_pat_expr(lit)),
         PatKind::Range(ref lower_bound, ref upper_bound, _) => {
-            visit_opt!(visitor, visit_expr, lower_bound);
-            visit_opt!(visitor, visit_expr, upper_bound);
+            visit_opt!(visitor, visit_pat_expr, lower_bound);
+            visit_opt!(visitor, visit_pat_expr, upper_bound);
         }
         PatKind::Never | PatKind::Wild | PatKind::Err(_) => (),
         PatKind::Slice(prepatterns, ref slice_pattern, postpatterns) => {
@@ -706,6 +709,15 @@ pub fn walk_pat_field<'v, V: Visitor<'v>>(visitor: &mut V, field: &'v PatField<'
     visitor.visit_pat(field.pat)
 }
 
+pub fn walk_pat_expr<'v, V: Visitor<'v>>(visitor: &mut V, lit: &'v PatExpr<'v>) -> V::Result {
+    try_visit!(visitor.visit_id(lit.hir_id));
+    match &lit.kind {
+        PatExprKind::Lit { .. } => V::Result::output(),
+        PatExprKind::ConstBlock(c) => visitor.visit_inline_const(c),
+        PatExprKind::Path(qpath) => visitor.visit_qpath(qpath, lit.hir_id, lit.span),
+    }
+}
+
 pub fn walk_anon_const<'v, V: Visitor<'v>>(visitor: &mut V, constant: &'v AnonConst) -> V::Result {
     try_visit!(visitor.visit_id(constant.hir_id));
     visitor.visit_nested_body(constant.body)

Diff for: compiler/rustc_hir_analysis/src/hir_ty_lowering/mod.rs

@@ -2449,17 +2449,11 @@ impl<'tcx> dyn HirTyLowerer<'tcx> + '_ {
                         Ty::new_error(tcx, err)
                     }
                     hir::PatKind::Range(start, end, include_end) => {
-                        let expr_to_const = |expr: &'tcx hir::Expr<'tcx>| -> ty::Const<'tcx> {
-                            let (expr, neg) = match expr.kind {
-                                hir::ExprKind::Unary(hir::UnOp::Neg, negated) => {
-                                    (negated, Some((expr.hir_id, expr.span)))
-                                }
-                                _ => (expr, None),
-                            };
-                            let (c, c_ty) = match &expr.kind {
-                                hir::ExprKind::Lit(lit) => {
+                        let expr_to_const = |expr: &'tcx hir::PatExpr<'tcx>| -> ty::Const<'tcx> {
+                            let (c, c_ty) = match expr.kind {
+                                hir::PatExprKind::Lit { lit, negated } => {
                                     let lit_input =
-                                        LitToConstInput { lit: &lit.node, ty, neg: neg.is_some() };
+                                        LitToConstInput { lit: &lit.node, ty, neg: negated };
                                     let ct = match tcx.lit_to_const(lit_input) {
                                         Ok(c) => c,
                                         Err(LitToConstError::Reported(err)) => {
@@ -2470,23 +2464,30 @@ impl<'tcx> dyn HirTyLowerer<'tcx> + '_ {
                                     (ct, ty)
                                 }
 
-                                hir::ExprKind::Path(hir::QPath::Resolved(
+                                hir::PatExprKind::Path(hir::QPath::Resolved(
                                     _,
                                     path @ &hir::Path {
                                         res: Res::Def(DefKind::ConstParam, def_id),
                                         ..
                                     },
                                 )) => {
-                                    let _ = self.prohibit_generic_args(
+                                    match self.prohibit_generic_args(
                                         path.segments.iter(),
                                         GenericsArgsErrExtend::Param(def_id),
-                                    );
-                                    let ty = tcx
-                                        .type_of(def_id)
-                                        .no_bound_vars()
-                                        .expect("const parameter types cannot be generic");
-                                    let ct = self.lower_const_param(def_id, expr.hir_id);
-                                    (ct, ty)
+                                    ) {
+                                        Ok(()) => {
+                                            let ty = tcx
+                                                .type_of(def_id)
+                                                .no_bound_vars()
+                                                .expect("const parameter types cannot be generic");
+                                            let ct = self.lower_const_param(def_id, expr.hir_id);
+                                            (ct, ty)
+                                        }
+                                        Err(guar) => (
+                                            ty::Const::new_error(tcx, guar),
+                                            Ty::new_error(tcx, guar),
+                                        ),
+                                    }
                                 }
 
                                 _ => {
@@ -2497,9 +2498,6 @@ impl<'tcx> dyn HirTyLowerer<'tcx> + '_ {
                                 }
                             };
                             self.record_ty(expr.hir_id, c_ty, expr.span);
-                            if let Some((id, span)) = neg {
-                                self.record_ty(id, c_ty, span);
-                            }
                             c
                         };
 

Diff for: compiler/rustc_hir_pretty/src/lib.rs

@@ -199,6 +199,7 @@ impl<'a> State<'a> {
             Node::OpaqueTy(o) => self.print_opaque_ty(o),
             Node::Pat(a) => self.print_pat(a),
             Node::PatField(a) => self.print_patfield(a),
+            Node::PatExpr(a) => self.print_pat_expr(a),
             Node::Arm(a) => self.print_arm(a),
             Node::Infer(_) => self.word("_"),
             Node::PreciseCapturingNonLifetimeArg(param) => self.print_ident(param.ident),
@@ -1849,6 +1850,19 @@ impl<'a> State<'a> {
         }
     }
 
+    fn print_pat_expr(&mut self, expr: &hir::PatExpr<'_>) {
+        match &expr.kind {
+            hir::PatExprKind::Lit { lit, negated } => {
+                if *negated {
+                    self.word("-");
+                }
+                self.print_literal(lit);
+            }
+            hir::PatExprKind::ConstBlock(c) => self.print_inline_const(c),
+            hir::PatExprKind::Path(qpath) => self.print_qpath(qpath, true),
+        }
+    }
+
     fn print_pat(&mut self, pat: &hir::Pat<'_>) {
         self.maybe_print_comment(pat.span.lo());
         self.ann.pre(self, AnnNode::Pat(pat));
@@ -1966,17 +1980,17 @@ impl<'a> State<'a> {
                     self.pclose();
                 }
             }
-            PatKind::Lit(e) => self.print_expr(e),
+            PatKind::Lit(e) => self.print_pat_expr(e),
             PatKind::Range(begin, end, end_kind) => {
                 if let Some(expr) = begin {
-                    self.print_expr(expr);
+                    self.print_pat_expr(expr);
                 }
                 match end_kind {
                     RangeEnd::Included => self.word("..."),
                     RangeEnd::Excluded => self.word(".."),
                 }
                 if let Some(expr) = end {
-                    self.print_expr(expr);
+                    self.print_pat_expr(expr);
                 }
             }
             PatKind::Slice(before, slice, after) => {