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Avoid defining let-bound variables on SMT level #948

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Avoid defining let-bound variables on SMT level #948

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16 changes: 12 additions & 4 deletions src/main/scala/rules/Evaluator.scala
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Original file line number Diff line number Diff line change
Expand Up @@ -250,10 +250,18 @@ object evaluator extends EvaluationRules {

case [email protected](x, e0, e1) =>
eval(s, e0, pve, v)((s1, t0, e0New, v1) => {
val t = v1.decider.appliedFresh("letvar", v1.symbolConverter.toSort(x.typ), s1.relevantQuantifiedVariables.map(_._1))
val debugExp = Option.when(withExp)(DebugExp.createInstance("letvar assignment", InsertionOrderedSet(DebugExp.createInstance(ast.EqCmp(x.localVar, e0)(), ast.EqCmp(x.localVar, e0New.get)()))))
v1.decider.assumeDefinition(BuiltinEquals(t, t0), debugExp)
val newFuncRec = s1.functionRecorder.recordFreshSnapshot(t.applicable.asInstanceOf[Function]).enterLet(l)
var newFuncRec = s1.functionRecorder.enterLet(l)
if (!s1.isMethodVerification && !(t0.isInstanceOf[Var] || t0.isInstanceOf[Literal])) {
// Make sure triggering terms make it to the SMT level; see Silver issue #688.
// We only do this in functions and predicates, since in those, let-bindings are basically the only
// way to introduce new triggering terms, and are frequently used to call lemma-functions etc.
// We want to do this as little as possible though, since the additional SMT-level terms can slow
// down verification a lot in some cases (e.g. Prusti produces a lot of let-bindings).
val t = v1.decider.appliedFresh("letvar", v1.symbolConverter.toSort(x.typ), s1.relevantQuantifiedVariables.map(_._1))
val debugExp = Option.when(withExp)(DebugExp.createInstance("letvar assignment", InsertionOrderedSet(DebugExp.createInstance(ast.EqCmp(x.localVar, e0)(), ast.EqCmp(x.localVar, e0New.get)()))))
v1.decider.assumeDefinition(BuiltinEquals(t, t0), debugExp)
newFuncRec = newFuncRec.recordFreshSnapshot(t.applicable.asInstanceOf[Function])
}
val possibleTriggersBefore = if (s1.recordPossibleTriggers) s1.possibleTriggers else Map.empty
eval(s1.copy(g = s1.g + (x.localVar, (t0, e0New)), functionRecorder = newFuncRec), e1, pve, v1)((s2, t2, e1New, v2) => {
val newPossibleTriggers = if (s2.recordPossibleTriggers) {
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