cgen: fix option unwrap on assignment (#17551)

vlib/v/checker/checker.v

@@ -1119,8 +1119,9 @@ fn (mut c Checker) check_or_last_stmt(stmt ast.Stmt, ret_type ast.Type, expr_ret
 				c.expected_or_type = ret_type.clear_flag(.option).clear_flag(.result)
 				last_stmt_typ := c.expr(stmt.expr)
 
-				if ret_type.has_flag(.option) && last_stmt_typ.has_flag(.option) {
-					if stmt.expr in [ast.Ident, ast.SelectorExpr, ast.CallExpr] {
+				if ret_type.has_flag(.option)
+					&& (last_stmt_typ.has_flag(.option) || last_stmt_typ == ast.none_type) {
+					if stmt.expr in [ast.Ident, ast.SelectorExpr, ast.CallExpr, ast.None] {
 						expected_type_name := c.table.type_to_str(ret_type.clear_flag(.option).clear_flag(.result))
 						got_type_name := c.table.type_to_str(last_stmt_typ)
 						c.error('`or` block must provide a value of type `${expected_type_name}`, not `${got_type_name}`',

vlib/v/checker/tests/wrong_option_unwrap_err.out

@@ -0,0 +1,7 @@
+vlib/v/checker/tests/wrong_option_unwrap_err.vv:3:14: error: `or` block must provide a value of type `string`, not `none`
+    1 | fn main() {
+    2 |     a := ?string('c')
+    3 |     b := a or { none }
+      |                 ~~~~
+    4 |     println(b)
+    5 | }

vlib/v/checker/tests/wrong_option_unwrap_err.vv

@@ -0,0 +1,5 @@
+fn main() {
+	a := ?string('c')
+	b := a or { none }
+	println(b)
+}

vlib/v/gen/c/assign.v

@@ -10,8 +10,8 @@ import v.token
 fn (mut g Gen) expr_with_opt_or_block(expr ast.Expr, expr_typ ast.Type, var_expr ast.Expr, ret_typ ast.Type) {
 	gen_or := expr is ast.Ident && (expr as ast.Ident).or_expr.kind != .absent
 	if gen_or {
-		old_inside_opt_data := g.inside_opt_data
-		g.inside_opt_data = true
+		old_inside_opt_or_res := g.inside_opt_or_res
+		g.inside_opt_or_res = true
 		g.expr_with_cast(expr, expr_typ, ret_typ)
 		g.writeln(';')
 		g.writeln('if (${expr}.state != 0) {')
@@ -40,7 +40,7 @@ fn (mut g Gen) expr_with_opt_or_block(expr ast.Expr, expr_typ ast.Type, var_expr
 			}
 		}
 		g.writeln('}')
-		g.inside_opt_data = old_inside_opt_data
+		g.inside_opt_or_res = old_inside_opt_or_res
 	} else {
 		g.expr_with_opt(expr, expr_typ, ret_typ)
 	}

vlib/v/gen/c/cgen.v

@@ -4093,7 +4093,7 @@ fn (mut g Gen) ident(node ast.Ident) {
 		if node.obj is ast.Var {
 			if !g.is_assign_lhs && node.obj.is_comptime_field {
 				if g.comptime_for_field_type.has_flag(.option) {
-					if (g.inside_opt_or_res && node.or_expr.kind == .absent) || g.left_is_opt {
+					if (g.inside_opt_or_res || g.left_is_opt) && node.or_expr.kind == .absent {
 						g.write('${name}')
 					} else {
 						g.write('/*opt*/')
@@ -4103,7 +4103,8 @@ fn (mut g Gen) ident(node ast.Ident) {
 				} else {
 					g.write('${name}')
 				}
-				if node.or_expr.kind != .absent {
+				if node.or_expr.kind != .absent && !(g.inside_opt_or_res && g.inside_assign
+					&& !g.is_assign_lhs) {
 					stmt_str := g.go_before_stmt(0).trim_space()
 					g.empty_line = true
 					g.or_block(name, node.or_expr, g.comptime_for_field_type)
@@ -4117,14 +4118,15 @@ fn (mut g Gen) ident(node ast.Ident) {
 		// `x = new_opt()` => `x = new_opt()` (g.right_is_opt == true)
 		// `println(x)` => `println(*(int*)x.data)`
 		if node.info.is_option && !(g.is_assign_lhs && g.right_is_opt) {
-			if (g.inside_opt_or_res && node.or_expr.kind == .absent) || g.left_is_opt {
+			if (g.inside_opt_or_res || g.left_is_opt) && node.or_expr.kind == .absent {
 				g.write('${name}')
 			} else {
 				g.write('/*opt*/')
 				styp := g.base_type(node.info.typ)
 				g.write('(*(${styp}*)${name}.data)')
 			}
-			if node.or_expr.kind != .absent && !(g.inside_assign && !g.is_assign_lhs) {
+			if node.or_expr.kind != .absent && !(g.inside_opt_or_res && g.inside_assign
+				&& !g.is_assign_lhs) {
 				stmt_str := g.go_before_stmt(0).trim_space()
 				g.empty_line = true
 				g.or_block(name, node.or_expr, node.info.typ)

vlib/v/tests/option_unwrap_assign_test.v

@@ -0,0 +1,15 @@
+struct Foo {
+mut:
+	x string
+	y ?string
+}
+
+fn test_main() {
+	a := ?string(none)
+	mut foo := Foo{}
+	foo.x = a or { 'test' }
+	foo.y = a or { 'test' }
+
+	assert foo.x == 'test'
+	assert foo.y? == 'test'
+}