[frontend] Add tests of using single field struct

Summary:
When a single field struct is initialized with "type x{v}" form, the translated result is not straightforward.  For example,

```
struct t {
  int val_;
};

void foo(t x) {
  t y{x};
}
```
calls the copy constructor with `x`.  This is good.

```
void foo(int n) {
  t y{n};
}
```
assigns the integer `n` to `y.val_`.  This is good.

```
t get_v();

void foo() {
  t y{get_v()};
}
```

assigns return value of `get_v` to `y.val_`, rather than calling the copy constructor.  This is not
good, but doesn't matter for actual running; `&y.val_` is the same to `&y` and `t` value is the same
to `int` value.

Reviewed By: jvillard

Differential Revision: D26146578

fbshipit-source-id: 8a81bb1db

infer/tests/codetoanalyze/cpp/pulse/frontend.cpp

@@ -203,4 +203,42 @@ void not_boolean_bad() {
   }
 }
 
+struct double_fields_struct {
+  int v;
+  int a;
+};
+
+double_fields_struct get_double_fields_struct() {
+  double_fields_struct b;
+  b.v = 42;
+  b.a = 42;
+  return b;
+}
+
+void init_double_fields_struct_ok() {
+  double_fields_struct y{get_double_fields_struct()};
+  if (y.v != 42) {
+    int* p = nullptr;
+    *p = 42;
+  }
+}
+
+struct single_field_struct {
+  int v;
+};
+
+single_field_struct get_single_field_struct() {
+  single_field_struct b;
+  b.v = 42;
+  return b;
+}
+
+void FP_init_single_field_struct_ok() {
+  single_field_struct y{get_single_field_struct()};
+  if (y.v != 42) {
+    int* p = nullptr;
+    *p = 42;
+  }
+}
+
 } // namespace frontend

infer/tests/codetoanalyze/cpp/pulse/issues.exp

@@ -32,6 +32,7 @@ codetoanalyze/cpp/pulse/deduplication.cpp, deduplication::templated_function_bad
 codetoanalyze/cpp/pulse/deduplication.cpp, deduplication::templated_function_bad<int>, 3, USE_AFTER_DELETE, no_bucket, ERROR, [invalidation part of the trace starts here,passed as argument to `new` (modelled),return from call to `new` (modelled),assigned,when calling `deduplication::templated_delete_function<int>` here,parameter `a` of deduplication::templated_delete_function<int>,was invalidated by `delete`,use-after-lifetime part of the trace starts here,passed as argument to `new` (modelled),return from call to `new` (modelled),assigned,when calling `deduplication::templated_access_function<int>` here,parameter `a` of deduplication::templated_access_function<int>,invalid access occurs here]
 codetoanalyze/cpp/pulse/exit_test.cpp, store_exit_null_bad, 0, NULLPTR_DEREFERENCE, no_bucket, ERROR, [invalidation part of the trace starts here,assigned,is the null pointer,use-after-lifetime part of the trace starts here,when calling `store_exit` here,parameter `x` of store_exit,invalid access occurs here]
 codetoanalyze/cpp/pulse/folly_DestructorGuard.cpp, UsingDelayedDestruction::double_delete_bad, 2, USE_AFTER_DELETE, no_bucket, ERROR, [invalidation part of the trace starts here,parameter `this` of UsingDelayedDestruction::double_delete_bad,was invalidated by `delete`,use-after-lifetime part of the trace starts here,parameter `this` of UsingDelayedDestruction::double_delete_bad,invalid access occurs here]
+codetoanalyze/cpp/pulse/frontend.cpp, frontend::FP_init_single_field_struct_ok, 4, NULLPTR_DEREFERENCE, no_bucket, ERROR, [invalidation part of the trace starts here,assigned,is the null pointer,use-after-lifetime part of the trace starts here,assigned,invalid access occurs here]
 codetoanalyze/cpp/pulse/frontend.cpp, frontend::call_Frontend_constructor2_bad, 5, NULLPTR_DEREFERENCE, no_bucket, ERROR, [invalidation part of the trace starts here,assigned,is the null pointer,use-after-lifetime part of the trace starts here,assigned,invalid access occurs here]
 codetoanalyze/cpp/pulse/frontend.cpp, frontend::call_Frontend_constructor_bad, 4, NULLPTR_DEREFERENCE, no_bucket, ERROR, [invalidation part of the trace starts here,assigned,is the null pointer,use-after-lifetime part of the trace starts here,assigned,invalid access occurs here]
 codetoanalyze/cpp/pulse/frontend.cpp, frontend::call_set_field_via_local_bad, 5, NULLPTR_DEREFERENCE, no_bucket, ERROR, [invalidation part of the trace starts here,assigned,is the null pointer,use-after-lifetime part of the trace starts here,assigned,invalid access occurs here]