checker: check struct field init with result value (fix #18511) (#18514)

vlib/v/checker/struct.v

@@ -509,11 +509,14 @@ fn (mut c Checker) struct_init(mut node ast.StructInit, is_field_zero_struct_ini
 				if got_type == ast.void_type {
 					c.error('`${init_field.expr}` (no value) used as value', init_field.pos)
 				}
-				if !exp_type.has_flag(.option) && !got_type.has_flag(.result) {
+				if !exp_type.has_flag(.option) {
 					got_type = c.check_expr_opt_call(init_field.expr, got_type)
 					if got_type.has_flag(.option) {
 						c.error('cannot assign an Option value to a non-option struct field',
 							init_field.pos)
+					} else if got_type.has_flag(.result) {
+						c.error('cannot assign a Result value to a non-option struct field',
+							init_field.pos)
 					}
 				}
 				if exp_type_sym.kind == .voidptr && got_type_sym.kind == .struct_

vlib/v/checker/tests/struct_field_init_with_result_err.out

@@ -0,0 +1,6 @@
+vlib/v/checker/tests/struct_field_init_with_result_err.vv:10:18: error: example() returns a Result, so it should have either an `or {}` block, or `!` at the end
+    8 |
+    9 | fn main() {
+   10 |     println(Example{example()})
+      |                     ~~~~~~~~~
+   11 | }

vlib/v/checker/tests/struct_field_init_with_result_err.vv

@@ -0,0 +1,11 @@
+fn example() !int {
+	return 0
+}
+
+struct Example {
+	example int
+}
+
+fn main() {
+	println(Example{example()})
+}