checker: add more checks for map.delete (fix #25204) (#25205)

vlib/v/checker/fn.v

@@ -3213,14 +3213,15 @@ fn (mut c Checker) map_builtin_method_call(mut node ast.CallExpr, left_type_ ast
 		}
 		'delete' {
 			c.check_for_mut_receiver(mut node.left)
-			if node.args.len != 1 {
-				c.error('expected 1 argument, but got ${node.args.len}', node.pos)
-			}
+			if node.args.len == 1 {
 				info := left_sym.info as ast.Map
 				arg_type := c.expr(mut node.args[0].expr)
 				c.check_expected_call_arg(arg_type, info.key_type, node.language, node.args[0]) or {
 					c.error('${err.msg()} in argument 1 to `Map.delete`', node.args[0].pos)
 				}
+			} else {
+				c.error('expected 1 argument, but got ${node.args.len}', node.pos)
+			}
 		}
 		else {}
 	}

vlib/v/checker/tests/map_delete.out

@@ -12,16 +12,29 @@ vlib/v/checker/tests/map_delete.vv:6:4: error: expected 1 argument, but got 2
       |       ~~~~~~~~~~~~
     7 |     m2 := {
     8 |         '1': 1
-vlib/v/checker/tests/map_delete.vv:6:11: error: cannot use `int literal` as `string` in argument 1 to `Map.delete`
-    4 |     }
-    5 |     m.delete(1)
-    6 |     m.delete(1, 2)
-      |              ^
-    7 |     m2 := {
-    8 |         '1': 1
 vlib/v/checker/tests/map_delete.vv:10:2: error: `m2` is immutable, declare it with `mut` to make it mutable
     8 |         '1': 1
     9 |     }
    10 |     m2.delete('1')
       |     ~~
-   11 | }
+   11 |     m.delete()
+   12 |     _ := m.delete()
+vlib/v/checker/tests/map_delete.vv:11:4: error: expected 1 argument, but got 0
+    9 |     }
+   10 |     m2.delete('1')
+   11 |     m.delete()
+      |       ~~~~~~~~
+   12 |     _ := m.delete()
+   13 | }
+vlib/v/checker/tests/map_delete.vv:12:9: error: expected 1 argument, but got 0
+   10 |     m2.delete('1')
+   11 |     m.delete()
+   12 |     _ := m.delete()
+      |            ~~~~~~~~
+   13 | }
+vlib/v/checker/tests/map_delete.vv:12:4: error: assignment mismatch: 1 variable but `delete()` returns 0 values
+   10 |     m2.delete('1')
+   11 |     m.delete()
+   12 |     _ := m.delete()
+      |       ~~
+   13 | }

vlib/v/checker/tests/map_delete.vv

@@ -8,4 +8,6 @@ fn main() {
 		'1': 1
 	}
 	m2.delete('1')
+	m.delete()
+	_ := m.delete()
 }