\section{Related Work}
\label{sect:related}

Experiments with adding types to Scheme go back more than twenty
years. Wand's Semantic Prototyping System~\cite{wand84sps} uses macros
to type-check implementations of denotational semantics.
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Typed Scheme scales up the approach of SPS to a modern macro and
module system, and it improves the interaction between typed and
untyped code.

Flanagan's static analyzer for DrScheme~\cite{ffkwf:mrspidey} analyzed
expanded programs and used syntax source information to display the
analysis results in the program editor. The analyzer included a macro
protocol that let programmers annotate their programs with hints to
the analyzer.
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Meunier's followup explored the use of type-imitating contracts to
modularize static analysis~\cite{meunier06modular}. Rather than
analyzing the entire program, the analysis uses contracts placed at
module boundaries to approximate the imported values.

The Ziggurat project~\cite{fisher06ziggurat} has investigated
alternate approaches to static analysis and other program observations
in the presence of macros. Analyses in Ziggurat are implemented as
methods on expression nodes, and derived expression forms (that is,
macros) may either override analysis methods with special behavior or
defer to the default analysis of the macro's expansion. Ziggurat
represents a new approach to defining macro protocols, and it is as
yet unclear how the Ziggurat approach compares with the mechanisms
described here.