checker: fail if else isn't the last branch of match

vlib/v/checker/checker.v

@@ -1355,7 +1355,17 @@ pub fn (c mut Checker) match_expr(node mut ast.MatchExpr) table.Type {
 		}
 		else {}
 	}
-	if !node.branches[node.branches.len - 1].is_else {
+	mut has_else := node.branches[node.branches.len - 1].is_else
+	if !has_else {
+		for i, branch in node.branches {
+			if branch.is_else && i != node.branches.len - 1 {
+				c.error('`else` must be the last branch of `match`', branch.pos)
+				has_else = true
+				break
+			}
+		}
+
+		if !has_else {
 			mut used_values_count := 0
 			for bi, branch in node.branches {
 				used_values_count += branch.exprs.len
@@ -1419,6 +1429,7 @@ pub fn (c mut Checker) match_expr(node mut ast.MatchExpr) table.Type {
 				c.error(err_details, node.pos)
 			}
 		}
+	}
 	c.expected_type = cond_type
 	mut ret_type := table.void_type
 	for branch in node.branches {

vlib/v/checker/tests/inout/match_else_last_expr.out

@@ -0,0 +1,7 @@
+vlib/v/checker/tests/inout/match_else_last_expr.v:4:3: error: `else` must be the last branch of `match`
+    2|     match 1 {
+    3|         1 { println('1') }
+    4|         else { println('else') }
+               ~~~~~~
+    5|         4 { println('4') }
+    6|     }

vlib/v/checker/tests/inout/match_else_last_expr.vv

@@ -0,0 +1,7 @@
+fn main() {
+	match 1 {
+		1 { println('1') }
+		else { println('else') }
+		4 { println('4') }
+	}
+}

vlib/v/parser/parser.v

@@ -1919,8 +1919,8 @@ fn (p mut Parser) match_expr() ast.MatchExpr {
 		// p.warn('match block')
 		stmts := p.parse_block()
 		pos := token.Position{
-			line_nr: match_first_pos.line_nr
+			line_nr: branch_first_pos.line_nr
-			pos: match_first_pos.pos
+			pos: branch_first_pos.pos
 			len: branch_last_pos.pos - branch_first_pos.pos + branch_last_pos.len
 		}
 		branches << ast.MatchBranch{