We were asserting in ExprRewriter::visitCoerceExpr() that the conversion
we attempt is successfully. However, we have known cases where we will
emit a diagnostic and fail attempting to convert, so we should really
just bail out at this point rather than asserting.
Resovles the last part of rdar://problem/28207648.
In the following code example, compiler emits an error of "cannot express tuple conversion...". However,
this is trivially fixable by adding multiple labels in the tuple pattern of the for-each statement. This
commit adds such fixit.
func foo(array : [(some: Int, (key: Int, value: String))]) {
for (i, (k, v)) in array {
}
}
