Parse subslice patterns within slice patterns

cc #1479

Author: tomjakubowski

crates/ra_parser/src/grammar/patterns.rs

@@ -145,7 +145,21 @@ fn path_pat(p: &mut Parser) -> CompletedMarker {
 fn tuple_pat_fields(p: &mut Parser) {
     assert!(p.at(T!['(']));
     p.bump();
-    pat_list(p, T![')']);
+    while !p.at(EOF) && !p.at(T![')']) {
+        match p.current() {
+            T![..] => p.bump(),
+            _ => {
+                if !p.at_ts(PATTERN_FIRST) {
+                    p.error("expected a pattern");
+                    break;
+                }
+                pattern(p)
+            }
+        }
+        if !p.at(T![')']) {
+            p.expect(T![,]);
+        }
+    }
     p.expect(T![')']);
 }
 
@@ -225,20 +239,21 @@ fn tuple_pat(p: &mut Parser) -> CompletedMarker {
 // test slice_pat
 // fn main() {
 //     let [a, b, ..] = [];
+//     let [a, b..] = [];
 // }
 fn slice_pat(p: &mut Parser) -> CompletedMarker {
     assert!(p.at(T!['[']));
     let m = p.start();
     p.bump();
-    pat_list(p, T![']']);
-    p.expect(T![']']);
-    m.complete(p, SLICE_PAT)
-}
-
-fn pat_list(p: &mut Parser, ket: SyntaxKind) {
-    while !p.at(EOF) && !p.at(ket) {
+    while !p.at(EOF) && !p.at(T![']']) {
         match p.current() {
             T![..] => p.bump(),
+            IDENT if p.nth(1) == T![..] => {
+                let m_sub = p.start();
+                p.bump();
+                p.bump();
+                m_sub.complete(p, SUBSLICE_PAT);
+            }
             _ => {
                 if !p.at_ts(PATTERN_FIRST) {
                     p.error("expected a pattern");
@@ -247,10 +262,12 @@ fn pat_list(p: &mut Parser, ket: SyntaxKind) {
                 pattern(p)
             }
         }
-        if !p.at(ket) {
+        if !p.at(T![']']) {
             p.expect(T![,]);
         }
     }
+    p.expect(T![']']);
+    m.complete(p, SLICE_PAT)
 }
 
 // test bind_pat

crates/ra_parser/src/syntax_kind/generated.rs

@@ -165,6 +165,7 @@ pub enum SyntaxKind {
     SLICE_PAT,
     RANGE_PAT,
     LITERAL_PAT,
+    SUBSLICE_PAT,
     TUPLE_EXPR,
     ARRAY_EXPR,
     PAREN_EXPR,
@@ -632,6 +633,7 @@ impl SyntaxKind {
             SLICE_PAT => &SyntaxInfo { name: "SLICE_PAT" },
             RANGE_PAT => &SyntaxInfo { name: "RANGE_PAT" },
             LITERAL_PAT => &SyntaxInfo { name: "LITERAL_PAT" },
+            SUBSLICE_PAT => &SyntaxInfo { name: "SUBSLICE_PAT" },
             TUPLE_EXPR => &SyntaxInfo { name: "TUPLE_EXPR" },
             ARRAY_EXPR => &SyntaxInfo { name: "ARRAY_EXPR" },
             PAREN_EXPR => &SyntaxInfo { name: "PAREN_EXPR" },

crates/ra_syntax/src/grammar.ron

@@ -168,6 +168,7 @@ Grammar(
         "SLICE_PAT",
         "RANGE_PAT",
         "LITERAL_PAT",
+        "SUBSLICE_PAT",
 
         // atoms
         "TUPLE_EXPR",
@@ -686,7 +687,7 @@ Grammar(
         "LifetimeArg": (),
 
         "MacroItems": (
-            traits: [ "ModuleItemOwner", "FnDefOwner" ],            
+            traits: [ "ModuleItemOwner", "FnDefOwner" ],
         ),
 
         "MacroStmts" : (

crates/ra_syntax/tests/data/parser/inline/ok/0024_slice_pat.rs

@@ -1,3 +1,4 @@
 fn main() {
     let [a, b, ..] = [];
+    let [a, b..] = [];
 }

crates/ra_syntax/tests/data/parser/inline/ok/0024_slice_pat.txt

@@ -1,5 +1,5 @@
-SOURCE_FILE@[0; 39)
-  FN_DEF@[0; 38)
+SOURCE_FILE@[0; 62)
+  FN_DEF@[0; 61)
     FN_KW@[0; 2) "fn"
     WHITESPACE@[2; 3) " "
     NAME@[3; 7)
@@ -8,7 +8,7 @@ SOURCE_FILE@[0; 39)
       L_PAREN@[7; 8) "("
       R_PAREN@[8; 9) ")"
     WHITESPACE@[9; 10) " "
-    BLOCK@[10; 38)
+    BLOCK@[10; 61)
       L_CURLY@[10; 11) "{"
       WHITESPACE@[11; 16) "\n    "
       LET_STMT@[16; 36)
@@ -35,6 +35,28 @@ SOURCE_FILE@[0; 39)
           L_BRACK@[33; 34) "["
           R_BRACK@[34; 35) "]"
         SEMI@[35; 36) ";"
-      WHITESPACE@[36; 37) "\n"
-      R_CURLY@[37; 38) "}"
-  WHITESPACE@[38; 39) "\n"
+      WHITESPACE@[36; 41) "\n    "
+      LET_STMT@[41; 59)
+        LET_KW@[41; 44) "let"
+        WHITESPACE@[44; 45) " "
+        SLICE_PAT@[45; 53)
+          L_BRACK@[45; 46) "["
+          BIND_PAT@[46; 47)
+            NAME@[46; 47)
+              IDENT@[46; 47) "a"
+          COMMA@[47; 48) ","
+          WHITESPACE@[48; 49) " "
+          SUBSLICE_PAT@[49; 52)
+            IDENT@[49; 50) "b"
+            DOTDOT@[50; 52) ".."
+          R_BRACK@[52; 53) "]"
+        WHITESPACE@[53; 54) " "
+        EQ@[54; 55) "="
+        WHITESPACE@[55; 56) " "
+        ARRAY_EXPR@[56; 58)
+          L_BRACK@[56; 57) "["
+          R_BRACK@[57; 58) "]"
+        SEMI@[58; 59) ";"
+      WHITESPACE@[59; 60) "\n"
+      R_CURLY@[60; 61) "}"
+  WHITESPACE@[61; 62) "\n"