Unable to infer @NonNegative property of elements in a double dimensional array.

Consider the following code:

import org.checkerframework.checker.index.qual.NonNegative;
class Issue2502{
    public void check_it(@NonNegative int x, @NonNegative int y){
         @NonNegative int a[][] = {{x},{y}};
    }  
}

Run it by typing in the terminal:
javac -processor index Issue2502.java

Output:

Issue2502.java:4: error: [assignment.type.incompatible] incompatible types in assignment.
@NonNegative int a[][] = {{x},{y}};
                       
  found   : @LowerBoundUnknown int @LowerBoundUnknown [] @LowerBoundUnknown []
  required: @NonNegative int @LowerBoundUnknown [] @LowerBoundUnknown []
1 error

Each value assigned in the array is non negative, but the checker still indicates error.

Reproduce the reported case from Issue2502.java by running javac -processor index Issue2502.java. Start by tracing the index checker’s handling of nested array initializers and qualifier inference; done means the shown @NonNegative declaration no longer produces an assignment.type.incompatible error.