Auto merge of #13096 - jonas-schievink:parse-more-or-pats, r=jonas-schievink

fix: Allow leading `|` in more pattern positions

fixes https://github.com/rust-lang/rust-analyzer/issues/12894, fixes https://github.com/rust-lang/rust-analyzer/issues/13094

Oddly, the leading `|` token does not end up inside the `OR_PAT` node, since `pattern_top_r` consumes it first. This is a preexisting issue in match arms though, so I didn't fix it here.

crates/parser/src/grammar/patterns.rs

@@ -13,6 +13,8 @@ pub(super) const PATTERN_FIRST: TokenSet =
         T![.],
     ]));
 
+const PAT_TOP_FIRST: TokenSet = PATTERN_FIRST.union(TokenSet::new(&[T![|]]));
+
 pub(crate) fn pattern(p: &mut Parser<'_>) {
     pattern_r(p, PAT_RECOVERY_SET);
 }
@@ -228,6 +230,7 @@ fn path_or_macro_pat(p: &mut Parser<'_>) -> CompletedMarker {
 //     let S(_) = ();
 //     let S(_,) = ();
 //     let S(_, .. , x) = ();
+//     let S(| a) = ();
 // }
 fn tuple_pat_fields(p: &mut Parser<'_>) {
     assert!(p.at(T!['(']));
@@ -363,6 +366,7 @@ fn ref_pat(p: &mut Parser<'_>) -> CompletedMarker {
 //     let (a,) = ();
 //     let (..) = ();
 //     let () = ();
+//     let (| a | a, | b) = ((),());
 // }
 fn tuple_pat(p: &mut Parser<'_>) -> CompletedMarker {
     assert!(p.at(T!['(']));
@@ -373,13 +377,13 @@ fn tuple_pat(p: &mut Parser<'_>) -> CompletedMarker {
     let mut has_rest = false;
     while !p.at(EOF) && !p.at(T![')']) {
         has_pat = true;
-        if !p.at_ts(PATTERN_FIRST) {
+        if !p.at_ts(PAT_TOP_FIRST) {
             p.error("expected a pattern");
             break;
         }
         has_rest |= p.at(T![..]);
 
-        pattern(p);
+        pattern_top(p);
         if !p.at(T![')']) {
             has_comma = true;
             p.expect(T![,]);
@@ -393,6 +397,7 @@ fn tuple_pat(p: &mut Parser<'_>) -> CompletedMarker {
 // test slice_pat
 // fn main() {
 //     let [a, b, ..] = [];
+//     let [| a, ..] = [];
 // }
 fn slice_pat(p: &mut Parser<'_>) -> CompletedMarker {
     assert!(p.at(T!['[']));
@@ -405,12 +410,12 @@ fn slice_pat(p: &mut Parser<'_>) -> CompletedMarker {
 
 fn pat_list(p: &mut Parser<'_>, ket: SyntaxKind) {
     while !p.at(EOF) && !p.at(ket) {
-        if !p.at_ts(PATTERN_FIRST) {
+        if !p.at_ts(PAT_TOP_FIRST) {
             p.error("expected a pattern");
             break;
         }
 
-        pattern(p);
+        pattern_top(p);
         if !p.at(ket) {
             p.expect(T![,]);
         }

crates/parser/test_data/parser/inline/ok/0024_slice_pat.rast

@@ -37,6 +37,29 @@ SOURCE_FILE
             L_BRACK "["
             R_BRACK "]"
           SEMICOLON ";"
+        WHITESPACE "\n    "
+        LET_STMT
+          LET_KW "let"
+          WHITESPACE " "
+          SLICE_PAT
+            L_BRACK "["
+            PIPE "|"
+            WHITESPACE " "
+            IDENT_PAT
+              NAME
+                IDENT "a"
+            COMMA ","
+            WHITESPACE " "
+            REST_PAT
+              DOT2 ".."
+            R_BRACK "]"
+          WHITESPACE " "
+          EQ "="
+          WHITESPACE " "
+          ARRAY_EXPR
+            L_BRACK "["
+            R_BRACK "]"
+          SEMICOLON ";"
         WHITESPACE "\n"
         R_CURLY "}"
   WHITESPACE "\n"

crates/parser/test_data/parser/inline/ok/0024_slice_pat.rs

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

crates/parser/test_data/parser/inline/ok/0026_tuple_pat_fields.rast

@@ -100,6 +100,29 @@ SOURCE_FILE
             L_PAREN "("
             R_PAREN ")"
           SEMICOLON ";"
+        WHITESPACE "\n    "
+        LET_STMT
+          LET_KW "let"
+          WHITESPACE " "
+          TUPLE_STRUCT_PAT
+            PATH
+              PATH_SEGMENT
+                NAME_REF
+                  IDENT "S"
+            L_PAREN "("
+            PIPE "|"
+            WHITESPACE " "
+            IDENT_PAT
+              NAME
+                IDENT "a"
+            R_PAREN ")"
+          WHITESPACE " "
+          EQ "="
+          WHITESPACE " "
+          TUPLE_EXPR
+            L_PAREN "("
+            R_PAREN ")"
+          SEMICOLON ";"
         WHITESPACE "\n"
         R_CURLY "}"
   WHITESPACE "\n"

crates/parser/test_data/parser/inline/ok/0026_tuple_pat_fields.rs

@@ -3,4 +3,5 @@ fn foo() {
     let S(_) = ();
     let S(_,) = ();
     let S(_, .. , x) = ();
+    let S(| a) = ();
 }

crates/parser/test_data/parser/inline/ok/0111_tuple_pat.rast

@@ -85,6 +85,46 @@ SOURCE_FILE
             L_PAREN "("
             R_PAREN ")"
           SEMICOLON ";"
+        WHITESPACE "\n    "
+        LET_STMT
+          LET_KW "let"
+          WHITESPACE " "
+          TUPLE_PAT
+            L_PAREN "("
+            PIPE "|"
+            WHITESPACE " "
+            OR_PAT
+              IDENT_PAT
+                NAME
+                  IDENT "a"
+              WHITESPACE " "
+              PIPE "|"
+              WHITESPACE " "
+              IDENT_PAT
+                NAME
+                  IDENT "a"
+            COMMA ","
+            WHITESPACE " "
+            PIPE "|"
+            WHITESPACE " "
+            IDENT_PAT
+              NAME
+                IDENT "b"
+            R_PAREN ")"
+          WHITESPACE " "
+          EQ "="
+          WHITESPACE " "
+          TUPLE_EXPR
+            L_PAREN "("
+            TUPLE_EXPR
+              L_PAREN "("
+              R_PAREN ")"
+            COMMA ","
+            TUPLE_EXPR
+              L_PAREN "("
+              R_PAREN ")"
+            R_PAREN ")"
+          SEMICOLON ";"
         WHITESPACE "\n"
         R_CURLY "}"
   WHITESPACE "\n"

crates/parser/test_data/parser/inline/ok/0111_tuple_pat.rs

@@ -3,4 +3,5 @@ fn main() {
     let (a,) = ();
     let (..) = ();
     let () = ();
+    let (| a | a, | b) = ((),());
 }