Make struct member access to work with `=` and `?:`

codegen.c

@@ -167,6 +167,13 @@ static void gen_addr(Node *node) {
       return;
     }
     break;
+  case ND_ASSIGN:
+  case ND_COND:
+    if (node->ty->kind == TY_STRUCT || node->ty->kind == TY_UNION) {
+      gen_expr(node);
+      return;
+    }
+    break;
   case ND_VLA_PTR:
     println("  lea %d(%%rbp), %%rax", node->var->offset);
     return;

test/struct.c

@@ -57,6 +57,10 @@ int main() {
   ASSERT(1, ({ struct T { struct T *next; int x; } a; struct T b; b.x=1; a.next=&b; a.next->x; }));
   ASSERT(4, ({ typedef struct T T; struct T { int x; }; sizeof(T); }));
 
+  ASSERT(2, ({ struct {int a;} x={1}, y={2}; (x=y).a; }));
+  ASSERT(1, ({ struct {int a;} x={1}, y={2}; (1?x:y).a; }));
+  ASSERT(2, ({ struct {int a;} x={1}, y={2}; (0?x:y).a; }));
+
   printf("OK\n");
   return 0;
 }