checker: check option and result handling in type-casted aliases (#16988)

vlib/v/checker/checker.v

@@ -992,6 +992,8 @@ fn (mut c Checker) check_expr_opt_call(expr ast.Expr, ret_type ast.Type) ast.Typ
 		if expr.or_expr.kind != .absent {
 			c.check_or_expr(expr.or_expr, ret_type, ret_type.set_flag(.result))
 		}
+	} else if expr is ast.CastExpr {
+		c.check_expr_opt_call(expr.expr, ret_type)
 	}
 	return ret_type
 }

vlib/v/checker/tests/alias_type_cast_option_result_unhandled_err.out

@@ -0,0 +1,13 @@
+vlib/v/checker/tests/alias_type_cast_option_result_unhandled_err.vv:15:12: error: ret_abc_result() returns a result, so it should have either an `or {}` block, or `!` at the end
+   13 | }
+   14 |
+   15 | a := Alias(ret_abc_result())
+      |            ~~~~~~~~~~~~~~~~
+   16 | b := Alias(ret_abc_option())
+   17 | println('${a}${b}')
+vlib/v/checker/tests/alias_type_cast_option_result_unhandled_err.vv:16:12: error: ret_abc_option() returns an option, so it should have either an `or {}` block, or `?` at the end
+   14 |
+   15 | a := Alias(ret_abc_result())
+   16 | b := Alias(ret_abc_option())
+      |            ~~~~~~~~~~~~~~~~
+   17 | println('${a}${b}')

vlib/v/checker/tests/alias_type_cast_option_result_unhandled_err.vv

@@ -0,0 +1,17 @@
+struct Abc {
+	a string
+}
+
+type Alias = Abc
+
+fn ret_abc_result() !Abc {
+	return Abc{'a'}
+}
+
+fn ret_abc_option() ?Abc {
+	return Abc{'a'}
+}
+
+a := Alias(ret_abc_result())
+b := Alias(ret_abc_option())
+println('${a}${b}')

vlib/v/checker/tests/cast_array_to_number_err.out

@@ -1,7 +1,7 @@
 vlib/v/checker/tests/cast_array_to_number_err.vv:5:8: error: cannot cast array `[]u8` to `i16`
     3 | fn main() {
     4 |     bytes := '010000150107120508d37445a0d7e5c5071980710c64310d9e12043000777369ff0424ab78b91a05164b00e50034003300'
-    5 |     yr := i16(hx.decode(bytes.substr(6,8))?)
+    5 |     yr := i16(hx.decode(bytes.substr(6,8))!)
       |           ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
     6 |     println(bytes)
     7 |     println('yr: $yr')

vlib/v/checker/tests/cast_array_to_number_err.vv

@@ -2,7 +2,7 @@ import encoding.hex as hx
 
 fn main() {
 	bytes := '010000150107120508d37445a0d7e5c5071980710c64310d9e12043000777369ff0424ab78b91a05164b00e50034003300'
-	yr := i16(hx.decode(bytes.substr(6,8))?)
+	yr := i16(hx.decode(bytes.substr(6,8))!)
 	println(bytes)
 	println('yr: $yr')
 }