Rollup merge of rust-lang#134228 - oli-obk:pat-lit-path, r=compiler-errors

Exhaustively handle expressions in patterns

We currently have this invariant in HIR that a `PatKind::Lit` or a `PatKind::Range` only contains

* `ExprKind::Lit`
* `ExprKind::UnOp(Neg, ExprKind::Lit)`
* `ExprKind::Path`
* `ExprKind::ConstBlock`

So I made `PatKind::Lit` and `PatKind::Range` stop containing `Expr`, and instead created a `PatLit` type whose `kind` enum only contains those variants.

The only place code got more complicated was in clippy, as it couldn't share as much anymore with `Expr` handling

It may be interesting on merging `ExprKind::{Path,Lit,ConstBlock}` in the future and using the same `PatLit` type (under a new name).

Then it should also be easier to eliminate any and all `UnOp(Neg, Lit) | Lit` matching that we have across the compiler. Some day we should fold the negation into the literal itself and just store it on the numeric literals

Author: matthiaskrgr

compiler/rustc_ast/src/ast.rs

@@ -623,7 +623,7 @@ impl Pat {
             PatKind::Wild
             | PatKind::Rest
             | PatKind::Never
-            | PatKind::Lit(_)
+            | PatKind::Expr(_)
             | PatKind::Range(..)
             | PatKind::Ident(..)
             | PatKind::Path(..)
@@ -801,8 +801,8 @@ pub enum PatKind {
     /// A reference pattern (e.g., `&mut (a, b)`).
     Ref(P<Pat>, Mutability),
 
-    /// A literal.
-    Lit(P<Expr>),
+    /// A literal, const block or path.
+    Expr(P<Expr>),
 
     /// A range pattern (e.g., `1...2`, `1..2`, `1..`, `..2`, `1..=2`, `..=2`).
     Range(Option<P<Expr>>, Option<P<Expr>>, Spanned<RangeEnd>),

compiler/rustc_ast/src/mut_visit.rs

@@ -1512,7 +1512,7 @@ pub fn walk_pat<T: MutVisitor>(vis: &mut T, pat: &mut P<Pat>) {
             vis.visit_ident(ident);
             visit_opt(sub, |sub| vis.visit_pat(sub));
         }
-        PatKind::Lit(e) => vis.visit_expr(e),
+        PatKind::Expr(e) => vis.visit_expr(e),
         PatKind::TupleStruct(qself, path, elems) => {
             vis.visit_qself(qself);
             vis.visit_path(path);

compiler/rustc_ast/src/visit.rs

@@ -680,7 +680,7 @@ pub fn walk_pat<'a, V: Visitor<'a>>(visitor: &mut V, pattern: &'a Pat) -> V::Res
             try_visit!(visitor.visit_ident(ident));
             visit_opt!(visitor, visit_pat, optional_subpattern);
         }
-        PatKind::Lit(expression) => try_visit!(visitor.visit_expr(expression)),
+        PatKind::Expr(expression) => try_visit!(visitor.visit_expr(expression)),
         PatKind::Range(lower_bound, upper_bound, _end) => {
             visit_opt!(visitor, visit_expr, lower_bound);
             visit_opt!(visitor, visit_expr, upper_bound);

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,

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| {

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)]

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::{
@@ -35,8 +38,8 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
                             lower_sub,
                         );
                     }
-                    PatKind::Lit(e) => {
-                        break hir::PatKind::Lit(self.lower_expr_within_pat(e, false));
+                    PatKind::Expr(e) => {
+                        break hir::PatKind::Expr(self.lower_expr_within_pat(e, false));
                     }
                     PatKind::TupleStruct(qself, path, pats) => {
                         let qpath = self.lower_qpath(
@@ -367,24 +370,54 @@ 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,
+        })
     }
 }

compiler/rustc_ast_pretty/src/pprust/state.rs

@@ -1701,7 +1701,7 @@ impl<'a> State<'a> {
                     self.print_pat(inner);
                 }
             }
-            PatKind::Lit(e) => self.print_expr(e, FixupContext::default()),
+            PatKind::Expr(e) => self.print_expr(e, FixupContext::default()),
             PatKind::Range(begin, end, Spanned { node: end_kind, .. }) => {
                 if let Some(e) = begin {
                     self.print_expr(e, FixupContext::default());

compiler/rustc_expand/src/base.rs

@@ -522,7 +522,7 @@ impl MacResult for MacEager {
                 return Some(P(ast::Pat {
                     id: ast::DUMMY_NODE_ID,
                     span: e.span,
-                    kind: PatKind::Lit(e),
+                    kind: PatKind::Expr(e),
                     tokens: None,
                 }));
             }

compiler/rustc_expand/src/build.rs

@@ -486,7 +486,7 @@ impl<'a> ExtCtxt<'a> {
         self.pat(span, PatKind::Wild)
     }
     pub fn pat_lit(&self, span: Span, expr: P<ast::Expr>) -> P<ast::Pat> {
-        self.pat(span, PatKind::Lit(expr))
+        self.pat(span, PatKind::Expr(expr))
     }
     pub fn pat_ident(&self, span: Span, ident: Ident) -> P<ast::Pat> {
         self.pat_ident_binding_mode(span, ident, ast::BindingMode::NONE)