instantiateFromExpression(expression.operands[0], axioms, freeVariable);
try {
WycsFile module = builder.getModule(expression.nid.module());
// module should not be null if TypePropagation has already passed.
WycsFile.Function fn = module.declaration(expression.nid.name(),
WycsFile.Function.class);
if (fn.constraint != null) {
// There are some axioms we can instantiate. First, we need to
// construct the generic binding for this function.
HashMap<String, SemanticType> generics = buildGenericBinding(