1. A system comprising: at least one processor: a memory connected to the at least one processor; and at least one program module that when loaded into the memory causes the at least one processor to: generate suggestions to correct an error comprising an undefined token in program source code by using an include graph for the project to find all the paths going from the node representing the file in which the token is defined in an external file to the project node; and displaying the topmost file in each directory as a suggestion along with the file in which the token is defined.