resolveVariable abstract method

Resolves the specified type variable to a concrete ResolvableType.

This method takes a type variable (such as T, K, V in generic declarations) and returns the concrete ResolvableType that the variable should resolve to in the current context.

Parameters:

• variable: The type variable to resolve

Returns:

• ResolvableType representing the resolved concrete type
• null if the variable cannot be resolved in this context

Example:

@override
ResolvableType? resolveVariable(Object variable) {
  if (variable == typeVariableT) {
    return ResolvableType.forClass(String);
  } else if (variable == typeVariableK) {
    return ResolvableType.forClass(int);
  }
  return null; // Cannot resolve this variable
}