cgen: fix or-block with return void statement (#17527)

vlib/v/gen/c/assign.v

@@ -20,8 +20,24 @@ fn (mut g Gen) expr_with_opt_or_block(expr ast.Expr, expr_typ ast.Type, var_expr
 			g.gen_option_error(g.cur_fn.return_type, expr)
 			g.writeln(';')
 		} else {
-			g.gen_or_block_stmts(var_expr.str(), '', (expr as ast.Ident).or_expr.stmts,
-				ret_typ, false)
+			g.inside_or_block = true
+			defer {
+				g.inside_or_block = false
+			}
+			stmts := (expr as ast.Ident).or_expr.stmts
+			// handles stmt block which returns something
+			// e.g. { return none }
+			if stmts.len > 0 && stmts.last() is ast.ExprStmt
+				&& (stmts.last() as ast.ExprStmt).typ != ast.void_type {
+				g.gen_or_block_stmts(var_expr.str(), '', stmts, ret_typ, false)
+			} else {
+				// handles stmt block which doesn't returns value
+				// e.g. { return }
+				g.stmts(stmts)
+				if stmts.len > 0 && stmts.last() is ast.ExprStmt {
+					g.writeln(';')
+				}
+			}
 		}
 		g.writeln('}')
 		g.inside_opt_data = old_inside_opt_data

vlib/v/tests/option_or_block_test.v

@@ -0,0 +1,14 @@
+fn foo(val ?int) {
+	if val == none {
+		a := val or { return }
+
+		assert false
+		println(a)
+	}
+	assert false
+}
+
+fn test_main() {
+	foo(none)
+	assert true
+}