Correctly parse <_> paths in patterns

closes #3659

crates/ra_parser/src/grammar/patterns.rs

@@ -88,7 +88,9 @@ fn atom_pat(p: &mut Parser, recovery_set: TokenSet) -> Option<CompletedMarker> {
             _ => bind_pat(p, true),
         },
 
-        _ if paths::is_use_path_start(p) => path_or_macro_pat(p),
+        // test type_path_in_pattern
+        // fn main() { let <_>::Foo = (); }
+        _ if paths::is_path_start(p) => path_or_macro_pat(p),
         _ if is_literal_pat_start(p) => literal_pat(p),
 
         T![.] if p.at(T![..]) => dot_dot_pat(p),
@@ -138,7 +140,7 @@ fn literal_pat(p: &mut Parser) -> CompletedMarker {
 //     let Bar(..) = ();
 // }
 fn path_or_macro_pat(p: &mut Parser) -> CompletedMarker {
-    assert!(paths::is_use_path_start(p));
+    assert!(paths::is_path_start(p));
     let m = p.start();
     paths::expr_path(p);
     let kind = match p.current() {

crates/ra_syntax/test_data/parser/err/0024_many_type_parens.rast

@@ -180,19 +180,20 @@ SOURCE_FILE@0..240
       EXPR_STMT@150..180
         TUPLE_EXPR@150..180
           L_PAREN@150..151 "("
-          BIN_EXPR@151..180
+          FOR_EXPR@151..180
-            BIN_EXPR@151..178
-              BIN_EXPR@151..169
-                BIN_EXPR@151..167
-                  BIN_EXPR@151..164
-                    FOR_EXPR@151..157
             FOR_KW@151..154 "for"
-                      ERROR@154..155
+            PATH_PAT@154..158
+              PATH@154..158
+                PATH_SEGMENT@154..158
                   L_ANGLE@154..155 "<"
                   ERROR@155..157
                     LIFETIME@155..157 "\'a"
                   R_ANGLE@157..158 ">"
             WHITESPACE@158..159 " "
+            BIN_EXPR@159..180
+              BIN_EXPR@159..178
+                BIN_EXPR@159..169
+                  BIN_EXPR@159..167
                     PATH_EXPR@159..164
                       PATH@159..164
                         PATH_SEGMENT@159..164
@@ -302,13 +303,12 @@ error 146..146: expected expression
 error 147..147: expected SEMICOLON
 error 148..148: expected expression
 error 149..149: expected SEMICOLON
-error 154..154: expected pattern
+error 155..155: expected type
-error 155..155: expected IN_KW
+error 158..158: expected IN_KW
-error 155..155: expected expression
-error 157..157: expected a block
 error 165..165: expected expression
 error 168..168: expected expression
 error 179..179: expected expression
+error 180..180: expected a block
 error 180..180: expected COMMA
 error 180..180: expected expression
 error 180..180: expected R_PAREN

crates/ra_syntax/test_data/parser/inline/ok/0164_type_path_in_pattern.rast

@@ -0,0 +1,38 @@
+SOURCE_FILE@0..33
+  FN_DEF@0..32
+    FN_KW@0..2 "fn"
+    WHITESPACE@2..3 " "
+    NAME@3..7
+      IDENT@3..7 "main"
+    PARAM_LIST@7..9
+      L_PAREN@7..8 "("
+      R_PAREN@8..9 ")"
+    WHITESPACE@9..10 " "
+    BLOCK_EXPR@10..32
+      L_CURLY@10..11 "{"
+      WHITESPACE@11..12 " "
+      LET_STMT@12..30
+        LET_KW@12..15 "let"
+        WHITESPACE@15..16 " "
+        PATH_PAT@16..24
+          PATH@16..24
+            PATH@16..19
+              PATH_SEGMENT@16..19
+                L_ANGLE@16..17 "<"
+                PLACEHOLDER_TYPE@17..18
+                  UNDERSCORE@17..18 "_"
+                R_ANGLE@18..19 ">"
+            COLON2@19..21 "::"
+            PATH_SEGMENT@21..24
+              NAME_REF@21..24
+                IDENT@21..24 "Foo"
+        WHITESPACE@24..25 " "
+        EQ@25..26 "="
+        WHITESPACE@26..27 " "
+        TUPLE_EXPR@27..29
+          L_PAREN@27..28 "("
+          R_PAREN@28..29 ")"
+        SEMICOLON@29..30 ";"
+      WHITESPACE@30..31 " "
+      R_CURLY@31..32 "}"
+  WHITESPACE@32..33 "\n"

crates/ra_syntax/test_data/parser/inline/ok/0164_type_path_in_pattern.rs

@@ -0,0 +1 @@
+fn main() { let <_>::Foo = (); }