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]>

1 files changed, 3 insertions, 0 deletions

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",