Fix compiler warnings for conditional expression bounds

[kkjeer]

Consider a conditional expression whose rvalue bounds depend on a variable that appears in only one arm:

array_ptr<int> y : count(5) = 0;
array_ptr<int> x : count(5) : cond ? y : 0;

The compiler infers bounds(y, y + 5) for the left arm, bounds(any) for the right arm, and bounds(y, y + 5) for the conditional expression cond ? y : 0. These bounds are used to validate the declared bounds bounds(x, x + 5) of x. Since it is not known that x and y are equivalent, this results in a compiler warning: "cannot prove declared bounds of 'x' are valid after initialization".

The logic outlined in the language spec for handling uses of temporaries bound in only one arm may be generalized to handle this case.