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Fix: Support for opaque function handles #4203

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merged 8 commits into from
Jun 22, 2023
Merged

Fix: Support for opaque function handles #4203

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aab2408
Add test for issue #4202
MikaelMayer Jun 20, 2023
9718664
Fix: Support for opaque function handles
MikaelMayer Jun 20, 2023
e320e75
FIXER:comp/TailRecursion.dfy
MikaelMayer Jun 21, 2023
365d378
Fixed CI tests
MikaelMayer Jun 21, 2023
efe8076
Merge branch 'master' into fix-4202-opaque-functions-passed-as-argume…
MikaelMayer Jun 21, 2023
1575d2e
Update Test/git-issues/git-issue-4202.dfy
MikaelMayer Jun 21, 2023
3512561
FIXER:git-issues/git-issue-4202.dfy
MikaelMayer Jun 21, 2023
6d43660
Fixed CI
MikaelMayer Jun 21, 2023
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12 changes: 10 additions & 2 deletions Source/DafnyCore/Verifier/Translator.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -5764,6 +5764,7 @@ public string FunctionHandle(Function f) {
functionHandles[f] = name;
var args = new List<Bpl.Expr>();
var vars = MkTyParamBinders(GetTypeParams(f), out args);
var argsRequires = new List<Bpl.Expr>(args); // Requires don't have reveal parameters
var formals = MkTyParamFormals(GetTypeParams(f), false, true);
var tyargs = new List<Bpl.Expr>();
foreach (var fm in f.Formals) {
Expand All @@ -5773,9 +5774,15 @@ public string FunctionHandle(Function f) {
if (f.IsFuelAware()) {
vars.Add(BplBoundVar("$ly", predef.LayerType, out var ly));
args.Add(ly);
argsRequires.Add(ly);
formals.Add(BplFormalVar("$fuel", predef.LayerType, true));
AddFuelSuccSynonymAxiom(f, true);
}
if (f.IsOpaque) {
vars.Add(BplBoundVar("$reveal", Boogie.Type.Bool, out var reveal));
args.Add(reveal);
formals.Add(BplFormalVar("$reveal", Boogie.Type.Bool, true));
}

Func<List<Bpl.Expr>, List<Bpl.Expr>> SnocSelf = x => x;
Func<List<Bpl.Expr>, List<Bpl.Expr>> SnocPrevH = x => x;
Expand Down Expand Up @@ -5817,6 +5824,7 @@ public string FunctionHandle(Function f) {
lhs_args.Add(fe);
var be = UnboxIfBoxed(fe, fm.Type);
rhs_args.Add(be);

rhs_dict[fm] = new BoogieWrapper(be, fm.Type);
// args and its [Box]args
var arg = BplBoundVar(fm_name, TrType(fm.Type), func_vars);
Expand Down Expand Up @@ -5845,7 +5853,7 @@ public string FunctionHandle(Function f) {
}

{
// Requires(Ty.., F#Handle( Ty1, ..., TyN, Layer, self), Heap, arg1, ..., argN)
// Requires(Ty.., F#Handle( Ty1, ..., TyN, Layer, reveal, self), Heap, arg1, ..., argN)
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Based on my initial experiments, this should make it easier to allow all functions to have a reveal parameter. The fact that requires didn't have this parameter was an awkward asymmetry.

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To be fair, we add the reveal parameter to the handle version of the function, not its requires. Since requirements and postconditions are always revealed, there is no need for a reveal parameter in .reveal

// = F#Requires(Ty1, .., TyN, Layer, Heap, self, [Unbox] arg1, .., [Unbox] argN)

var fhandle = FunctionCall(f.tok, name, predef.HandleType, SnocSelf(SnocPrevH(args)));
Expand All @@ -5855,7 +5863,7 @@ public string FunctionHandle(Function f) {
// In case this is the /requires/ or /reads/ function, then there is no precondition
rhs = Bpl.Expr.True;
} else {
var args_h = f.ReadsHeap ? Snoc(SnocPrevH(args), h) : args;
var args_h = f.ReadsHeap ? Snoc(SnocPrevH(argsRequires), h) : argsRequires;
rhs = FunctionCall(f.tok, RequiresName(f), Bpl.Type.Bool, Concat(SnocSelf(args_h), rhs_args));
}

Expand Down
16 changes: 16 additions & 0 deletions Test/git-issues/git-issue-4202.dfy
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@@ -0,0 +1,16 @@
// RUN: %baredafny verify %args "%s" > "%t"
// RUN: %diff "%s.expect" "%t"

opaque function F(x: int): char
{ 'D' }

function InitArray<D>(f: int -> D): (a: D)
{
f(44)
}

method Main() {
reveal F();
var c := InitArray(F);
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assert c == 'D';
}
2 changes: 2 additions & 0 deletions Test/git-issues/git-issue-4202.dfy.expect
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@@ -0,0 +1,2 @@

Dafny program verifier finished with 1 verified, 0 errors
1 change: 1 addition & 0 deletions docs/dev/news/4202.fix
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@@ -0,0 +1 @@
Support for opaque function handles