Merge #1848

1848: Parse `..` as a full pattern r=matklad a=ecstatic-morse

Resolves #1479.

This PR implements [RFC 2707](rust-lang/rfcs#2707) in the parser. It introduces a new `DotDotPat` AST node modeled on `PlaceholderPat` and changes the parsing of tuple and slice patterns to conform to the RFC.

Notably, this PR does *not* change the resulting AST when `..` appears in a struct pattern (e.g. `Struct { a, b: c, .. }`). I *think* this is the behavior mandated by RFC 2707, but someone should confirm this.

Co-authored-by: Dylan MacKenzie <ecstaticmorse@gmail.com>

crates/ra_hir/src/expr/lower.rs

@@ -573,6 +573,7 @@ where
  }
 
  // FIXME: implement
+ ast::Pat::DotDotPat(_) => Pat::Missing,
  ast::Pat::BoxPat(_) => Pat::Missing,
  ast::Pat::LiteralPat(_) => Pat::Missing,
  ast::Pat::SlicePat(_) | ast::Pat::RangePat(_) => Pat::Missing,

crates/ra_parser/src/grammar/patterns.rs

@@ -2,7 +2,7 @@ use super::*;
 
 pub(super) const PATTERN_FIRST: TokenSet = expressions::LITERAL_FIRST
  .union(paths::PATH_FIRST)
- .union(token_set![BOX_KW, REF_KW, MUT_KW, L_PAREN, L_BRACK, AMP, UNDERSCORE, MINUS]);
+ .union(token_set![BOX_KW, REF_KW, MUT_KW, L_PAREN, L_BRACK, AMP, UNDERSCORE, MINUS, DOT]);
 
 pub(crate) fn pattern(p: &mut Parser) {
  pattern_r(p, PAT_RECOVERY_SET);
@@ -73,6 +73,7 @@ fn atom_pat(p: &mut Parser, recovery_set: TokenSet) -> Option<CompletedMarker> {
  _ if paths::is_use_path_start(p) => path_pat(p),
  _ if is_literal_pat_start(p) => literal_pat(p),
 
+ T![.] if p.at(T![..]) => dot_dot_pat(p),
  T![_] => placeholder_pat(p),
  T![&] => ref_pat(p),
  T!['('] => tuple_pat(p),
@@ -163,7 +164,9 @@ fn record_field_pat_list(p: &mut Parser) {
  p.bump_any();
  while !p.at(EOF) && !p.at(T!['}']) {
  match p.current() {
+ // A trailing `..` is *not* treated as a DOT_DOT_PAT.
  T![.] if p.at(T![..]) => p.bump(T![..]),
+
  IDENT if p.nth(1) == T![:] => record_field_pat(p),
  T!['{'] => error_block(p, "expected ident"),
  T![box] => {
@@ -201,6 +204,39 @@ fn placeholder_pat(p: &mut Parser) -> CompletedMarker {
  m.complete(p, PLACEHOLDER_PAT)
 }
 
+// test dot_dot_pat
+// fn main() {
+// let .. = ();
+// //
+// // Tuples
+// //
+// let (a, ..) = ();
+// let (a, ..,) = ();
+// let Tuple(a, ..) = ();
+// let Tuple(a, ..,) = ();
+// let (.., ..) = ();
+// let Tuple(.., ..) = ();
+// let (.., a, ..) = ();
+// let Tuple(.., a, ..) = ();
+// //
+// // Slices
+// //
+// let [..] = ();
+// let [head, ..] = ();
+// let [head, tail @ ..] = ();
+// let [head, .., cons] = ();
+// let [head, mid @ .., cons] = ();
+// let [head, .., .., cons] = ();
+// let [head, .., mid, tail @ ..] = ();
+// let [head, .., mid, .., cons] = ();
+// }
+fn dot_dot_pat(p: &mut Parser) -> CompletedMarker {
+ assert!(p.at(T![..]));
+ let m = p.start();
+ p.bump(T![..]);
+ m.complete(p, DOT_DOT_PAT)
+}
+
 // test ref_pat
 // fn main() {
 // let &a = ();
@@ -241,16 +277,12 @@ fn slice_pat(p: &mut Parser) -> CompletedMarker {
 
 fn pat_list(p: &mut Parser, ket: SyntaxKind) {
  while !p.at(EOF) && !p.at(ket) {
- match p.current() {
- T![.] if p.at(T![..]) => p.bump(T![..]),
- _ => {
- if !p.at_ts(PATTERN_FIRST) {
- p.error("expected a pattern");
- break;
- }
- pattern(p)
- }
+ if !p.at_ts(PATTERN_FIRST) {
+ p.error("expected a pattern");
+ break;
  }
+
+ pattern(p);
  if !p.at(ket) {
  p.expect(T![,]);
  }

crates/ra_parser/src/syntax_kind/generated.rs

@@ -152,6 +152,7 @@ pub enum SyntaxKind {
  BOX_PAT,
  BIND_PAT,
  PLACEHOLDER_PAT,
+ DOT_DOT_PAT,
  PATH_PAT,
  RECORD_PAT,
  RECORD_FIELD_PAT_LIST,

crates/ra_syntax/src/ast/generated.rs

@@ -532,6 +532,29 @@ impl AstNode for ContinueExpr {
 }
 impl ContinueExpr {}
 #[derive(Debug, Clone, PartialEq, Eq, Hash)]
+pub struct DotDotPat {
+ pub(crate) syntax: SyntaxNode,
+}
+impl AstNode for DotDotPat {
+ fn can_cast(kind: SyntaxKind) -> bool {
+ match kind {
+ DOT_DOT_PAT => true,
+ _ => false,
+ }
+ }
+ fn cast(syntax: SyntaxNode) -> Option<Self> {
+ if Self::can_cast(syntax.kind()) {
+ Some(Self { syntax })
+ } else {
+ None
+ }
+ }
+ fn syntax(&self) -> &SyntaxNode {
+ &self.syntax
+ }
+}
+impl DotDotPat {}
+#[derive(Debug, Clone, PartialEq, Eq, Hash)]
 pub struct DynTraitType {
  pub(crate) syntax: SyntaxNode,
 }
@@ -2128,6 +2151,7 @@ pub enum Pat {
  BoxPat(BoxPat),
  BindPat(BindPat),
  PlaceholderPat(PlaceholderPat),
+ DotDotPat(DotDotPat),
  PathPat(PathPat),
  RecordPat(RecordPat),
  TupleStructPat(TupleStructPat),
@@ -2156,6 +2180,11 @@ impl From<PlaceholderPat> for Pat {
  Pat::PlaceholderPat(node)
  }
 }
+impl From<DotDotPat> for Pat {
+ fn from(node: DotDotPat) -> Pat {
+ Pat::DotDotPat(node)
+ }
+}
 impl From<PathPat> for Pat {
  fn from(node: PathPat) -> Pat {
  Pat::PathPat(node)
@@ -2194,8 +2223,10 @@ impl From<LiteralPat> for Pat {
 impl AstNode for Pat {
  fn can_cast(kind: SyntaxKind) -> bool {
  match kind {
- REF_PAT | BOX_PAT | BIND_PAT | PLACEHOLDER_PAT | PATH_PAT | RECORD_PAT
- | TUPLE_STRUCT_PAT | TUPLE_PAT | SLICE_PAT | RANGE_PAT | LITERAL_PAT => true,
+ REF_PAT | BOX_PAT | BIND_PAT | PLACEHOLDER_PAT | DOT_DOT_PAT | PATH_PAT
+ | RECORD_PAT | TUPLE_STRUCT_PAT | TUPLE_PAT | SLICE_PAT | RANGE_PAT | LITERAL_PAT => {
+ true
+ }
  _ => false,
  }
  }
@@ -2205,6 +2236,7 @@ impl AstNode for Pat {
  BOX_PAT => Pat::BoxPat(BoxPat { syntax }),
  BIND_PAT => Pat::BindPat(BindPat { syntax }),
  PLACEHOLDER_PAT => Pat::PlaceholderPat(PlaceholderPat { syntax }),
+ DOT_DOT_PAT => Pat::DotDotPat(DotDotPat { syntax }),
  PATH_PAT => Pat::PathPat(PathPat { syntax }),
  RECORD_PAT => Pat::RecordPat(RecordPat { syntax }),
  TUPLE_STRUCT_PAT => Pat::TupleStructPat(TupleStructPat { syntax }),
@@ -2222,6 +2254,7 @@ impl AstNode for Pat {
  Pat::BoxPat(it) => &it.syntax,
  Pat::BindPat(it) => &it.syntax,
  Pat::PlaceholderPat(it) => &it.syntax,
+ Pat::DotDotPat(it) => &it.syntax,
  Pat::PathPat(it) => &it.syntax,
  Pat::RecordPat(it) => &it.syntax,
  Pat::TupleStructPat(it) => &it.syntax,

crates/ra_syntax/src/grammar.ron

@@ -161,6 +161,7 @@ Grammar(
  "BOX_PAT",
  "BIND_PAT",
  "PLACEHOLDER_PAT",
+ "DOT_DOT_PAT",
  "PATH_PAT",
  "RECORD_PAT",
  "RECORD_FIELD_PAT_LIST",
@@ -532,6 +533,7 @@ Grammar(
  traits: ["NameOwner"]
  ),
  "PlaceholderPat": (),
+ "DotDotPat": (),
  "PathPat": ( options: [ "Path" ] ),
  "RecordPat": ( options: ["RecordFieldPatList", "Path"] ),
  "RecordFieldPatList": (
@@ -559,6 +561,7 @@ Grammar(
  "BoxPat",
  "BindPat",
  "PlaceholderPat",
+ "DotDotPat",
  "PathPat",
  "RecordPat",
  "TupleStructPat",

crates/ra_syntax/test_data/parser/inline/ok/0008_path_part.txt

@@ -82,7 +82,8 @@ SOURCE_FILE@[0; 103)
  NAME_REF@[87; 90)
  IDENT@[87; 90) "Bar"
  L_PAREN@[90; 91) "("
- DOTDOT@[91; 93) ".."
+ DOT_DOT_PAT@[91; 93)
+ DOTDOT@[91; 93) ".."
  R_PAREN@[93; 94) ")"
  WHITESPACE@[94; 95) " "
  EQ@[95; 96) "="

crates/ra_syntax/test_data/parser/inline/ok/0024_slice_pat.txt

@@ -27,7 +27,8 @@ SOURCE_FILE@[0; 39)
  IDENT@[24; 25) "b"
  COMMA@[25; 26) ","
  WHITESPACE@[26; 27) " "
- DOTDOT@[27; 29) ".."
+ DOT_DOT_PAT@[27; 29)
+ DOTDOT@[27; 29) ".."
  R_BRACK@[29; 30) "]"
  WHITESPACE@[30; 31) " "
  EQ@[31; 32) "="

crates/ra_syntax/test_data/parser/inline/ok/0026_tuple_pat_fields.txt

@@ -84,7 +84,8 @@ SOURCE_FILE@[0; 97)
  UNDERSCORE@[78; 79) "_"
  COMMA@[79; 80) ","
  WHITESPACE@[80; 81) " "
- DOTDOT@[81; 83) ".."
+ DOT_DOT_PAT@[81; 83)
+ DOTDOT@[81; 83) ".."
  WHITESPACE@[83; 84) " "
  COMMA@[84; 85) ","
  WHITESPACE@[85; 86) " "

crates/ra_syntax/test_data/parser/inline/ok/0111_tuple_pat.txt

@@ -27,7 +27,8 @@ SOURCE_FILE@[0; 39)
  IDENT@[24; 25) "b"
  COMMA@[25; 26) ","
  WHITESPACE@[26; 27) " "
- DOTDOT@[27; 29) ".."
+ DOT_DOT_PAT@[27; 29)
+ DOTDOT@[27; 29) ".."
  R_PAREN@[29; 30) ")"
  WHITESPACE@[30; 31) " "
  EQ@[31; 32) "="

crates/ra_syntax/test_data/parser/inline/ok/0144_dot_dot_pat.rs

@@ -0,0 +1,25 @@
+fn main() {
+ let .. = ();
+ //
+ // Tuples
+ //
+ let (a, ..) = ();
+ let (a, ..,) = ();
+ let Tuple(a, ..) = ();
+ let Tuple(a, ..,) = ();
+ let (.., ..) = ();
+ let Tuple(.., ..) = ();
+ let (.., a, ..) = ();
+ let Tuple(.., a, ..) = ();
+ //
+ // Slices
+ //
+ let [..] = ();
+ let [head, ..] = ();
+ let [head, tail @ ..] = ();
+ let [head, .., cons] = ();
+ let [head, mid @ .., cons] = ();
+ let [head, .., .., cons] = ();
+ let [head, .., mid, tail @ ..] = ();
+ let [head, .., mid, .., cons] = ();
+}