Have Alloy developers used any parser generator tool (like ANTLR) for parsing alloy specifications, or is its parser built-in and specifically written for the alloy language purpose?
If they used external tool for Alloy parser implementation, how can I access further information regarding this (for example the grammar which is fed into the external parser generator).
Alloy uses a modified version of CUP (which is shipped with the Alloy distribution). You can find the grammar specification files (Alloy.lex and Alloy.cup) inside the edu.mit.csail.sdg.alloy4compiler.parser package. In the same package there are some bash scripts used to generate corresponding lexer/parser classes.