Constraint not generated correctly for chained DesignatedInitExpr

[john-h-kastner]

I noticed this issue while investigating the test failure in PR #474. The field x is converted to _Ptr<int> even though it's initialized to 1. This is converted correctly if we instead initialize c with {{1}}.

struct a {
  int *x;
};

struct b {
  struct a y;
};

void foo(){
  struct b c = {.y.x = 1};
}

Broadly what happens is that we only see a InitListExpr for the outer struct b. The RecursiveASTVisitor never visits an expression for initializing the inner struct a. The ast dump for the variable declartion shows two InitListExpr, so clearly clang is able to transform this sort of designated initialization to initialization lists, but I guess this hasn't happened for the AST that we traverse.

      `-VarDecl 0x55e9fda02ca8 <col:3, col:25> col:12 c 'struct b':'struct b' cinit
        `-InitListExpr 0x55e9fda02e80 <col:16, col:25> 'struct b':'struct b'
          `-InitListExpr 0x55e9fda02ec8 <col:19, col:24> 'struct a':'struct a'
            `-ImplicitCastExpr 0x55e9fda02f10 <col:24> 'int *' <IntegralToPointer>
              `-IntegerLiteral 0x55e9fda02d20 <col:24> 'int' 1