checker: check `match` with type alias (#10863)

vlib/v/checker/checker.v

@@ -6085,6 +6085,7 @@ fn (mut c Checker) match_exprs(mut node ast.MatchExpr, cond_type_sym ast.TypeSym
 				// parser failed, stop checking
 				return
 			}
+			expr_type_sym := c.table.get_type_symbol(expr_type)
 			if cond_type_sym.kind == .interface_ {
 				// TODO
 				// This generates a memory issue with TCC
@@ -6094,7 +6095,6 @@ fn (mut c Checker) match_exprs(mut node ast.MatchExpr, cond_type_sym ast.TypeSym
 				expr_pos := expr.position()
 				if c.type_implements(expr_type, c.expected_type, expr_pos) {
 					if !expr_type.is_ptr() && !expr_type.is_pointer() && !c.inside_unsafe {
-						expr_type_sym := c.table.get_type_symbol(expr_type)
 						if expr_type_sym.kind != .interface_ {
 							c.mark_as_referenced(mut &branch.exprs[k], true)
 						}
@@ -6106,10 +6106,14 @@ fn (mut c Checker) match_exprs(mut node ast.MatchExpr, cond_type_sym ast.TypeSym
 					expect_str := c.table.type_to_str(node.cond_type)
 					c.error('`$expect_str` has no variant `$expr_str`', expr.position())
 				}
+			} else if cond_type_sym.info is ast.Alias && expr_type_sym.info is ast.Struct {
+				expr_str := c.table.type_to_str(expr_type)
+				expect_str := c.table.type_to_str(node.cond_type)
+				c.error('cannot match alias type `$expect_str` with `$expr_str`', expr.position())
 			} else if !c.check_types(expr_type, node.cond_type) {
 				expr_str := c.table.type_to_str(expr_type)
 				expect_str := c.table.type_to_str(node.cond_type)
-				c.error('cannot match `$expr_str` with `$expect_str` condition', expr.position())
+				c.error('cannot match `$expect_str` with `$expr_str`', expr.position())
 			}
 			branch_exprs[key] = val + 1
 		}

vlib/v/checker/tests/match_alias_type_err.out

@@ -0,0 +1,7 @@
+vlib/v/checker/tests/match_alias_type_err.vv:13:3: error: cannot match alias type `Stmt` with `SelectStmt`
+   11 | 
+   12 |     match stmt {
+   13 |         SelectStmt { panic('select') }
+      |         ~~~~~~~~~~
+   14 |         else { /* why? */ }
+   15 |     }

vlib/v/checker/tests/match_alias_type_err.vv

@@ -0,0 +1,16 @@
+type Stmt = SelectStmt
+
+struct SelectStmt {}
+
+fn parse(sql string) Stmt {
+	return SelectStmt{}
+}
+
+fn main() {
+	stmt := parse('select 123')
+
+	match stmt {
+		SelectStmt { panic('select') }
+		else { /* why? */ }
+	}
+}

vlib/v/checker/tests/match_expr_and_expected_type_error.out

@@ -1,11 +1,11 @@
-vlib/v/checker/tests/match_expr_and_expected_type_error.vv:3:3: error: cannot match `string` with `rune` condition
+vlib/v/checker/tests/match_expr_and_expected_type_error.vv:3:3: error: cannot match `rune` with `string`
     1 | ch := `a`
     2 | match ch {
     3 |   'a' {}
       |   ~~~
     4 |   else {}
     5 | }
-vlib/v/checker/tests/match_expr_and_expected_type_error.vv:9:3: error: cannot match `string` with `int` condition
+vlib/v/checker/tests/match_expr_and_expected_type_error.vv:9:3: error: cannot match `int` with `string`
     7 | i := 123
     8 | match i {
     9 |   'a' {}

vlib/v/checker/tests/match_undefined_cond.out

@@ -5,14 +5,14 @@ vlib/v/checker/tests/match_undefined_cond.vv:4:15: error: undefined ident: `Asd`
       |                  ~~~
     5 |         1 { 'foo' }
     6 |         2 { 'test' }
-vlib/v/checker/tests/match_undefined_cond.vv:5:3: error: cannot match `int literal` with `void` condition
+vlib/v/checker/tests/match_undefined_cond.vv:5:3: error: cannot match `void` with `int literal`
     3 | fn main() {
     4 |     res := match Asd {
     5 |         1 { 'foo' }
       |         ^
     6 |         2 { 'test' }
     7 |         else { '' }
-vlib/v/checker/tests/match_undefined_cond.vv:6:3: error: cannot match `int literal` with `void` condition
+vlib/v/checker/tests/match_undefined_cond.vv:6:3: error: cannot match `void` with `int literal`
     4 |     res := match Asd {
     5 |         1 { 'foo' }
     6 |         2 { 'test' }