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Merge pull request #802 from viperproject/meilers_dont_count_requires…
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…_as_pre

Allow domain axioms to use functions that have decreases clauses
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marcoeilers authored Jun 25, 2024
2 parents aa72715 + 0769bf5 commit 93bc9b7
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8 changes: 7 additions & 1 deletion src/main/scala/viper/silver/parser/Resolver.scala
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package viper.silver.parser

import viper.silver.FastMessaging
import viper.silver.parser.PKw.Requires

import scala.collection.mutable

Expand Down Expand Up @@ -685,8 +686,13 @@ case class TypeChecker(names: NameAnalyser) {
check(fd.typ)
fd.formalArgs foreach (a => check(a.typ))
}
if (pfa.isDescendant[PAxiom] && pfn.pres.length != 0)
if (pfa.isDescendant[PAxiom] && pfn.pres.toSeq.exists(pre => pre.k.rs == Requires)) {
// A domain axiom, which must always be well-defined, is calling a function that has at least
// one real precondition (i.e., not just a requires clause or something similar that's
// temporarily represented as a precondition), which means that the call may not always be
// well-defined. This is not allowed.
issueError(func, s"Cannot use function ${func.name}, which has preconditions, inside axiom")
}

case pdf: PDomainFunction =>
val domain = pdf.domain
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68 changes: 68 additions & 0 deletions src/test/resources/all/issues/silicon/0847.vpr
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@@ -0,0 +1,68 @@
// Any copyright is dedicated to the Public Domain.
// http://creativecommons.org/publicdomain/zero/1.0/


function f1(i: Int): Int
decreases i
requires i > -2
{
i > 0 ? 1 + f1(i - 1) : 0
}

function f2(i: Int): Int
decreases i
{
i > 0 ? 1 + f2(i - 1) : 0
}

function f3(i: Int): Int
decreases i
ensures result >= 0
{
i > 0 ? 1 + f3(i - 1) : 0
}

function f4(i: Int): Int
ensures result >= 0
decreases _
{
i > 0 ? 1 + f4(i - 1) : 0
}

function f5(i: Int): Int
requires i > -2
decreases i
ensures result >= 0
{
i > 0 ? 1 + f5(i - 1) : 0
}

domain t {
function fAlias1(Int): Int
function fAlias2(Int): Int
function fAlias3(Int): Int
function fAlias4(Int): Int
function fAlias5(Int): Int

axiom {
//:: ExpectedOutput(typechecker.error)
forall i: Int :: f1(i) == fAlias1(i)
}

axiom {
forall i: Int :: f2(i) == fAlias2(i)
}

axiom {
forall i: Int :: f3(i) == fAlias3(i)
}

axiom {
forall i: Int :: f4(i) == fAlias4(i)
}

axiom {
//:: ExpectedOutput(typechecker.error)
forall i: Int :: f5(i) == fAlias5(i)
}
}

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