Merge #1848

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

Resolves #1479.

This PR implements [RFC 2707](https://github.com/rust-lang/rfcs/pull/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 <[email protected]>

2 files changed, 38 insertions, 2 deletions

diff --git a/crates/ra_syntax/src/ast/generated.rs b/crates/ra_syntax/src/ast/generated.rs
index a8a231ef3..591ac8ca3 100644
--- a/crates/ra_syntax/src/ast/generated.rs
+++ b/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,
diff --git a/crates/ra_syntax/src/grammar.ron b/crates/ra_syntax/src/grammar.ron
index 8f064711d..08cc6eeea 100644
--- a/crates/ra_syntax/src/grammar.ron
+++ b/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",