fmt: remove extra comma of branch instead of parse error (#12814)

vlib/v/fmt/tests/match_expected.vv

@@ -36,3 +36,15 @@ fn really_long_branch_exprs() {
 		}
 	}
 }
+
+fn match_branch_extra_comma() {
+	match x {
+		Foo, Bar {}
+		int, string {}
+	}
+	match n {
+		0...5 {}
+		2, 3 {}
+		else {}
+	}
+}

vlib/v/fmt/tests/match_input.vv

@@ -34,3 +34,15 @@ fn really_long_branch_exprs() {
 		}
 	}
 }
+
+fn match_branch_extra_comma() {
+	match x {
+		Foo, Bar, {}
+		int,,, string, {}
+	}
+	match n {
+		0...5, {}
+		2, 3, {}
+		else {}
+	}
+}

vlib/v/parser/if_match.v

@@ -197,6 +197,14 @@ fn (mut p Parser) match_expr() ast.MatchExpr {
 					break
 				}
 				p.check(.comma)
+				if p.pref.is_fmt {
+					if p.tok.kind == .lcbr {
+						break
+					}
+					for p.tok.kind == .comma {
+						p.next()
+					}
+				}
 			}
 			is_sum_type = true
 		} else {
@@ -226,7 +234,16 @@ fn (mut p Parser) match_expr() ast.MatchExpr {
 				if p.tok.kind != .comma {
 					break
 				}
+
 				p.check(.comma)
+				if p.pref.is_fmt {
+					if p.tok.kind == .lcbr {
+						break
+					}
+					for p.tok.kind == .comma {
+						p.next()
+					}
+				}
 			}
 		}
 		branch_last_pos := p.prev_tok.position()