Attribute propagation by message passing

The goal of our work is to use the paradigms of syntax-directed editing to perform very sophisticated semantic checking, for example, to check flow-sensitive properties such as whether a variable is necessarily defined before it is used. Semantic checking of this power is much more important than syntax checking because it relieves the programmer of the need to keep track of numerous details as the program grows in complexity. There has been a great deal of recent work on syntax-directed editing. This work primarily serves the needs of novice programmers: making the task of entering and editing programs easier and less error prone. Most syntax-directed editors guarantee that the program fragment under construction is syntactically correct at all times. Many of them also detect simple semantic errors such as undeclared variables or type errors. Few, however, attempt to perform more semantic analysis than a typical (non-optimizing) compiler.