Split the test

crates/parser/src/grammar/patterns.rs

@@ -69,12 +69,20 @@ fn pattern_single_r(p: &mut Parser, recovery_set: TokenSet) {
         //         302 .. => (),
         //     }
         // }
+
+        // FIXME: support half_open_range_patterns (`..=2`),
+        // exclusive_range_pattern (`..5`) with missing lhs
         for &range_op in [T![...], T![..=], T![..]].iter() {
             if p.at(range_op) {
                 let m = lhs.precede(p);
                 p.bump(range_op);
-                if !p.at(T![=>]) {
+
-                    // not a range pat like `302 .. => ()`
+                // `0 .. =>` or `let 0 .. =`
+                //       ^                ^
+                if p.at(T![=]) {
+                    // test half_open_range_pat
+                    // fn f() { let 0 .. = 1u32; }
+                } else {
                     atom_pat(p, recovery_set);
                 }
                 m.complete(p, RANGE_PAT);

crates/syntax/test_data/parser/inline/ok/0166_half_open_range_pat.rast

@@ -0,0 +1,31 @@
+SOURCE_FILE@0..28
+  FN@0..27
+    FN_KW@0..2 "fn"
+    WHITESPACE@2..3 " "
+    NAME@3..4
+      IDENT@3..4 "f"
+    PARAM_LIST@4..6
+      L_PAREN@4..5 "("
+      R_PAREN@5..6 ")"
+    WHITESPACE@6..7 " "
+    BLOCK_EXPR@7..27
+      L_CURLY@7..8 "{"
+      WHITESPACE@8..9 " "
+      LET_STMT@9..25
+        LET_KW@9..12 "let"
+        WHITESPACE@12..13 " "
+        RANGE_PAT@13..17
+          LITERAL_PAT@13..14
+            LITERAL@13..14
+              INT_NUMBER@13..14 "0"
+          WHITESPACE@14..15 " "
+          DOT2@15..17 ".."
+        WHITESPACE@17..18 " "
+        EQ@18..19 "="
+        WHITESPACE@19..20 " "
+        LITERAL@20..24
+          INT_NUMBER@20..24 "1u32"
+        SEMICOLON@24..25 ";"
+      WHITESPACE@25..26 " "
+      R_CURLY@26..27 "}"
+  WHITESPACE@27..28 "\n"

crates/syntax/test_data/parser/inline/ok/0166_half_open_range_pat.rs

@@ -0,0 +1 @@
+fn f() { let 0 .. = 1u32; }