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copybara-service merged 1 commit into from
Aug 1, 2026
Merged

Mark uninterpreted conversions with literals as approximate #1155

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4 changes: 3 additions & 1 deletion verifier/src/main/java/dev/cel/verifier/CelAstToZ3Translator.java
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Original file line number Diff line number Diff line change
Expand Up @@ -741,8 +741,10 @@ private TranslatedValue translateCall(CelExpr expr, CelAbstractSyntaxTree ast) {
typeConstraints.add(ctx.mkNot(typeSystem.isUnknown(callRes)));
typeConstraints.add(ctx.mkNot(typeSystem.isError(callRes)));

boolean isDynamic = ast.getType(exprId).map(SimpleType.DYN::equals).orElse(true);
BoolExpr isApprox = ctx.mkBool(!isDynamic);
return TranslatedValue.propagateStrict(
ctx, typeSystem, callRes, Optional.of(expr), ctx.mkTrue(), args);
ctx, typeSystem, callRes, Optional.of(expr), isApprox, args);
});
}

Expand Down
3 changes: 2 additions & 1 deletion verifier/src/main/java/dev/cel/verifier/CelZ3OperatorTranslator.java
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Expand Up @@ -594,7 +594,8 @@ private TranslatedValue translateEquality(
// because X == X is a tautology (or propagates errors/unknowns exactly).
if (z3Arg0.equals(z3Arg1)) {
Expr<?> finalResult = typeSystem.propagateErrorAndUnknown(equalityExpr, z3Arg0);
return TranslatedValue.create(finalResult, typeSystem, ctx.mkFalse());
return TranslatedValue.create(
finalResult, typeSystem, ctx.mkOr(arg0.isApproximate(), arg1.isApproximate()));
}

return TranslatedValue.propagateStrict(ctx, typeSystem, equalityExpr, arg0, arg1)
Expand Down
30 changes: 30 additions & 0 deletions verifier/src/main/java/dev/cel/verifier/CelZ3TypeSystem.java
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Expand Up @@ -26,6 +26,7 @@
import com.microsoft.z3.DatatypeSort;
import com.microsoft.z3.Expr;
import com.microsoft.z3.FPExpr;
import com.microsoft.z3.FPNum;
import com.microsoft.z3.FuncDecl;
import com.microsoft.z3.IntExpr;
import com.microsoft.z3.SeqExpr;
Expand Down Expand Up @@ -280,6 +281,35 @@ Constructor optionalCons() {
return optionalCons;
}

/**
* Checks if the given CelValue expression represents a statically known primitive constant.
*
* <p>This is useful for determining whether an uninterpreted function's result should be treated
* as an approximation. If the argument is a known constant, any resulting error is an
* approximation (e.g., parsing a literal string). If it's a variable, the error is an exact
* runtime failure.
*/
public boolean isPrimitiveConstant(Expr<?> expr) {
if (!expr.isApp()) {
return false;
}
FuncDecl<?> decl = expr.getFuncDecl();
if (decl.equals(stringCons.ConstructorDecl()) || decl.equals(bytesCons.ConstructorDecl())) {
return expr.getArgs()[0].isString();
} else if (decl.equals(intCons.ConstructorDecl())
|| decl.equals(uintCons.ConstructorDecl())
|| decl.equals(timestampCons.ConstructorDecl())
|| decl.equals(durationCons.ConstructorDecl())) {
return expr.getArgs()[0].isNumeral();
} else if (decl.equals(doubleCons.ConstructorDecl())) {
return expr.getArgs()[0] instanceof FPNum;
} else if (decl.equals(boolCons.ConstructorDecl())) {
Expr<?> inner = expr.getArgs()[0];
return inner.isTrue() || inner.isFalse();
}
return false;
}

/** Creates a CelValue containing a boolean. */
public Expr<?> mkBool(boolean val) {
return ctx.mkApp(boolCons.ConstructorDecl(), ctx.mkBool(val));
Expand Down
153 changes: 75 additions & 78 deletions verifier/src/main/java/dev/cel/verifier/axioms/TypeConversionAxioms.java
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Expand Up @@ -19,11 +19,13 @@
import com.google.common.collect.ImmutableList;
import com.microsoft.z3.BoolExpr;
import com.microsoft.z3.Expr;
import com.microsoft.z3.FPExpr;
import com.microsoft.z3.FuncDecl;
import com.microsoft.z3.IntExpr;
import com.microsoft.z3.Sort;
import dev.cel.checker.CelStandardDeclarations.StandardFunction;
import dev.cel.checker.CelStandardDeclarations.StandardFunction.Overload.Conversions;
import dev.cel.common.types.SimpleType;
import java.util.Optional;

/** Axiomatization for CEL's type conversion functions. */
Expand All @@ -42,14 +44,12 @@ final class TypeConversionAxioms {
return Optional.of(
typeSystem.withRuntimeError(typeSystem.wrapInt(uintVal), outOfBounds));
})
.addUnaryOverloadTranslator(
.addOverloadTranslator(
Conversions.DOUBLE_TO_INT64.celOverloadDecl(),
createUninterpretedConversion(Conversions.DOUBLE_TO_INT64),
/* isApproximated= */ true)
.addUnaryOverloadTranslator(
createUninterpretedConversion(Conversions.DOUBLE_TO_INT64))
.addOverloadTranslator(
Conversions.STRING_TO_INT64.celOverloadDecl(),
createUninterpretedConversion(Conversions.STRING_TO_INT64),
/* isApproximated= */ true)
createUninterpretedConversion(Conversions.STRING_TO_INT64))
.addUnaryOverloadTranslator(
Conversions.TIMESTAMP_TO_INT64.celOverloadDecl(),
(ctx, typeSystem, sink, arg) ->
Expand All @@ -69,79 +69,66 @@ final class TypeConversionAxioms {
return Optional.of(
typeSystem.withRuntimeError(typeSystem.wrapUint(intVal), outOfBounds));
})
.addUnaryOverloadTranslator(
.addOverloadTranslator(
Conversions.DOUBLE_TO_UINT64.celOverloadDecl(),
createUninterpretedConversion(Conversions.DOUBLE_TO_UINT64),
/* isApproximated= */ true)
.addUnaryOverloadTranslator(
createUninterpretedConversion(Conversions.DOUBLE_TO_UINT64))
.addOverloadTranslator(
Conversions.STRING_TO_UINT64.celOverloadDecl(),
createUninterpretedConversion(Conversions.STRING_TO_UINT64),
/* isApproximated= */ true)
createUninterpretedConversion(Conversions.STRING_TO_UINT64))
.build();

private static final CelZ3FunctionAxiom DOUBLE_AXIOM =
CelZ3FunctionAxiom.newBuilder(StandardFunction.DOUBLE.functionDecl())
.addUnaryOverloadTranslator(
Conversions.DOUBLE_TO_DOUBLE.celOverloadDecl(),
(ctx, typeSystem, sink, arg) -> Optional.of(arg))
.addUnaryOverloadTranslator(
.addOverloadTranslator(
Conversions.INT64_TO_DOUBLE.celOverloadDecl(),
createUninterpretedConversion(Conversions.INT64_TO_DOUBLE),
/* isApproximated= */ true)
.addUnaryOverloadTranslator(
createUninterpretedConversion(Conversions.INT64_TO_DOUBLE))
.addOverloadTranslator(
Conversions.UINT64_TO_DOUBLE.celOverloadDecl(),
createUninterpretedConversion(Conversions.UINT64_TO_DOUBLE),
/* isApproximated= */ true)
.addUnaryOverloadTranslator(
createUninterpretedConversion(Conversions.UINT64_TO_DOUBLE))
.addOverloadTranslator(
Conversions.STRING_TO_DOUBLE.celOverloadDecl(),
createUninterpretedConversion(Conversions.STRING_TO_DOUBLE),
/* isApproximated= */ true)
createUninterpretedConversion(Conversions.STRING_TO_DOUBLE))
.build();

private static final CelZ3FunctionAxiom STRING_AXIOM =
CelZ3FunctionAxiom.newBuilder(StandardFunction.STRING.functionDecl())
.addUnaryOverloadTranslator(
Conversions.STRING_TO_STRING.celOverloadDecl(),
(ctx, typeSystem, sink, arg) -> Optional.of(arg))
.addUnaryOverloadTranslator(
.addOverloadTranslator(
Conversions.INT64_TO_STRING.celOverloadDecl(),
createUninterpretedConversion(Conversions.INT64_TO_STRING),
/* isApproximated= */ true)
.addUnaryOverloadTranslator(
createUninterpretedConversion(Conversions.INT64_TO_STRING))
.addOverloadTranslator(
Conversions.UINT64_TO_STRING.celOverloadDecl(),
createUninterpretedConversion(Conversions.UINT64_TO_STRING),
/* isApproximated= */ true)
.addUnaryOverloadTranslator(
createUninterpretedConversion(Conversions.UINT64_TO_STRING))
.addOverloadTranslator(
Conversions.DOUBLE_TO_STRING.celOverloadDecl(),
createUninterpretedConversion(Conversions.DOUBLE_TO_STRING),
/* isApproximated= */ true)
.addUnaryOverloadTranslator(
createUninterpretedConversion(Conversions.DOUBLE_TO_STRING))
.addOverloadTranslator(
Conversions.BOOL_TO_STRING.celOverloadDecl(),
createUninterpretedConversion(Conversions.BOOL_TO_STRING),
/* isApproximated= */ true)
.addUnaryOverloadTranslator(
createUninterpretedConversion(Conversions.BOOL_TO_STRING))
.addOverloadTranslator(
Conversions.BYTES_TO_STRING.celOverloadDecl(),
createUninterpretedConversion(Conversions.BYTES_TO_STRING),
/* isApproximated= */ true)
.addUnaryOverloadTranslator(
createUninterpretedConversion(Conversions.BYTES_TO_STRING))
.addOverloadTranslator(
Conversions.TIMESTAMP_TO_STRING.celOverloadDecl(),
createUninterpretedConversion(Conversions.TIMESTAMP_TO_STRING),
/* isApproximated= */ true)
.addUnaryOverloadTranslator(
createUninterpretedConversion(Conversions.TIMESTAMP_TO_STRING))
.addOverloadTranslator(
Conversions.DURATION_TO_STRING.celOverloadDecl(),
createUninterpretedConversion(Conversions.DURATION_TO_STRING),
/* isApproximated= */ true)
createUninterpretedConversion(Conversions.DURATION_TO_STRING))
.build();

private static final CelZ3FunctionAxiom BYTES_AXIOM =
CelZ3FunctionAxiom.newBuilder(StandardFunction.BYTES.functionDecl())
.addUnaryOverloadTranslator(
Conversions.BYTES_TO_BYTES.celOverloadDecl(),
(ctx, typeSystem, sink, arg) -> Optional.of(arg))
.addUnaryOverloadTranslator(
.addOverloadTranslator(
Conversions.STRING_TO_BYTES.celOverloadDecl(),
createUninterpretedConversion(Conversions.STRING_TO_BYTES),
/* isApproximated= */ true)
createUninterpretedConversion(Conversions.STRING_TO_BYTES))
.build();

private static final CelZ3FunctionAxiom DYN_AXIOM =
Expand All @@ -156,21 +143,19 @@ final class TypeConversionAxioms {
.addUnaryOverloadTranslator(
Conversions.DURATION_TO_DURATION.celOverloadDecl(),
(ctx, typeSystem, sink, arg) -> Optional.of(arg))
.addUnaryOverloadTranslator(
.addOverloadTranslator(
Conversions.STRING_TO_DURATION.celOverloadDecl(),
createUninterpretedConversion(Conversions.STRING_TO_DURATION),
/* isApproximated= */ true)
createUninterpretedConversion(Conversions.STRING_TO_DURATION))
.build();

private static final CelZ3FunctionAxiom TIMESTAMP_AXIOM =
CelZ3FunctionAxiom.newBuilder(StandardFunction.TIMESTAMP.functionDecl())
.addUnaryOverloadTranslator(
Conversions.TIMESTAMP_TO_TIMESTAMP.celOverloadDecl(),
(ctx, typeSystem, sink, arg) -> Optional.of(arg))
.addUnaryOverloadTranslator(
.addOverloadTranslator(
Conversions.STRING_TO_TIMESTAMP.celOverloadDecl(),
createUninterpretedConversion(Conversions.STRING_TO_TIMESTAMP),
/* isApproximated= */ true)
createUninterpretedConversion(Conversions.STRING_TO_TIMESTAMP))
.addUnaryOverloadTranslator(
Conversions.INT64_TO_TIMESTAMP.celOverloadDecl(),
(ctx, typeSystem, sink, arg) -> {
Expand All @@ -186,10 +171,9 @@ final class TypeConversionAxioms {
.addUnaryOverloadTranslator(
Conversions.BOOL_TO_BOOL.celOverloadDecl(),
(ctx, typeSystem, sink, arg) -> Optional.of(arg))
.addUnaryOverloadTranslator(
.addOverloadTranslator(
Conversions.STRING_TO_BOOL.celOverloadDecl(),
createUninterpretedConversion(Conversions.STRING_TO_BOOL),
/* isApproximated= */ true)
createUninterpretedConversion(Conversions.STRING_TO_BOOL))
.build();

static final ImmutableList<CelZ3FunctionAxiom> ALL_AXIOMS =
Expand All @@ -204,64 +188,77 @@ final class TypeConversionAxioms {
TIMESTAMP_AXIOM,
BOOL_AXIOM);

private static CelZ3FunctionAxiom.UnaryTranslator createUninterpretedConversion(
Conversions conversion) {
return (ctx, typeSystem, sink, arg) -> {
private static CelZ3OverloadTranslator createUninterpretedConversion(Conversions conversion) {
return (ctx, typeSystem, sink, unwrappedArgs, argApproximations) -> {
Expr<?> arg = unwrappedArgs.get(0);
BoolExpr baseApprox = argApproximations.get(0);

FuncDecl<?> funcDecl =
typeSystem.internFuncDecl(
conversion.celOverloadDecl().overloadId(),
new Sort[] {typeSystem.celValueSort()},
typeSystem.celValueSort());
Expr<?> res = ctx.mkApp(funcDecl, arg);

BoolExpr isValid;
switch (conversion.celOverloadDecl().resultType().kind()) {
case INT:
isValid =
ctx.mkAnd(
sink.accept(ctx.mkOr(typeSystem.isInt(res), typeSystem.isError(res)));
sink.accept(
ctx.mkImplies(
typeSystem.isInt(res),
ctx.mkNot(typeSystem.checkIntOverflow(typeSystem.getInt(res))));
ctx.mkNot(typeSystem.checkIntOverflow(typeSystem.getInt(res)))));
break;
case TIMESTAMP:
isValid =
ctx.mkAnd(
sink.accept(ctx.mkOr(typeSystem.isTimestamp(res), typeSystem.isError(res)));
sink.accept(
ctx.mkImplies(
typeSystem.isTimestamp(res),
ctx.mkNot(typeSystem.checkTimestampOverflow(typeSystem.getTimestamp(res))));
ctx.mkNot(typeSystem.checkTimestampOverflow(typeSystem.getTimestamp(res)))));
break;
case DURATION:
isValid =
ctx.mkAnd(
sink.accept(ctx.mkOr(typeSystem.isDuration(res), typeSystem.isError(res)));
sink.accept(
ctx.mkImplies(
typeSystem.isDuration(res),
ctx.mkNot(typeSystem.checkDurationOverflow(typeSystem.getDuration(res))));
ctx.mkNot(typeSystem.checkDurationOverflow(typeSystem.getDuration(res)))));
break;
case UINT:
isValid =
ctx.mkAnd(
sink.accept(ctx.mkOr(typeSystem.isUint(res), typeSystem.isError(res)));
sink.accept(
ctx.mkImplies(
typeSystem.isUint(res),
ctx.mkNot(typeSystem.checkUintOverflow(typeSystem.getUint(res))));
ctx.mkNot(typeSystem.checkUintOverflow(typeSystem.getUint(res)))));
break;
case DOUBLE:
isValid =
ctx.mkAnd(
typeSystem.isDouble(res), ctx.mkNot(ctx.mkFPIsNaN(typeSystem.getDouble(res))));
sink.accept(ctx.mkOr(typeSystem.isDouble(res), typeSystem.isError(res)));
sink.accept(
ctx.mkImplies(
typeSystem.isDouble(res),
ctx.mkNot(ctx.mkFPIsNaN((FPExpr) typeSystem.getDouble(res)))));
break;
case STRING:
isValid = typeSystem.isString(res);
sink.accept(ctx.mkOr(typeSystem.isString(res), typeSystem.isError(res)));
break;
case BYTES:
isValid = typeSystem.isBytes(res);
sink.accept(ctx.mkOr(typeSystem.isBytes(res), typeSystem.isError(res)));
break;
case BOOL:
isValid = typeSystem.isBool(res);
sink.accept(ctx.mkOr(typeSystem.isBool(res), typeSystem.isError(res)));
break;
default:
throw new IllegalArgumentException(
"Unsupported uninterpreted conversion result type: "
+ conversion.celOverloadDecl().resultType());
}

sink.accept(ctx.mkOr(isValid, typeSystem.isError(res)));
return Optional.of(res);
boolean isArgConstant = typeSystem.isPrimitiveConstant(arg);
boolean isStringParseConversion =
conversion.celOverloadDecl().parameterTypes().get(0).equals(SimpleType.STRING);

BoolExpr finalApprox =
(!isArgConstant && isStringParseConversion) ? baseApprox : ctx.mkTrue();

return Optional.of(CelZ3OverloadResult.create(res, finalApprox));
};
}

Expand Down
17 changes: 9 additions & 8 deletions verifier/src/test/java/dev/cel/verifier/CelVerifierZ3ImplTest.java
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Expand Up @@ -154,8 +154,6 @@ private enum IsSatisfiableTestCase {
NULL_SATISFIABLE("unknown_var == null"),
DYNAMIC_VAR_NUMERIC_EQUALITY("dyn_var == 1 && dyn_var == 1.0"),
DYNAMIC_VAR_NOT_IN_LIST("dyn_var == 1.5 && !(dyn_var in dyn_list) && size(dyn_list) > 5"),
TIMESTAMP_EQUALITY_TAUTOLOGY(
"timestamp('2023-01-01T00:00:00Z') == timestamp('2023-01-01T00:00:00Z')"),
CROSS_NUMERIC_EQUALITY_INT_DYN_EXACT("1 == request"),
MACRO_LIMIT("dyn_list.all(x, x == 1)"),
STRUCT_FIELD_MISSING_APPROXIMATE_SATISFIABLE("dyn_var.unknown_field"),
Expand Down Expand Up @@ -1353,12 +1351,10 @@ private enum IsAlwaysTrueViolationTestCase {
"duration(string_var) == duration(string_var)",
"Condition is not always true\\.",
"Counterexample input:"),
// TODO: Implement RFC 3339 spec in conversion
TIMESTAMP_STRING_CONVERSION_VALID(
"timestamp('2023-01-01T00:00:00Z') == timestamp('2023-01-01T00:00:00Z')",
"Condition is not always true\\."),
DURATION_STRING_CONVERSION_VALID(
"duration('100s') == duration('100s')", "Condition is not always true\\."),
UNINTERPRETED_CONVERSION_CAN_ERROR_BOOL_FROM_STRING(
"bool(string_var) == bool(string_var)",
"Condition is not always true\\.",
"Counterexample input:"),
;

final String expr;
Expand All @@ -1384,6 +1380,11 @@ public void isAlwaysTrue_violation_returnsFalse(
}

private enum IsInconclusiveTestCase {
// TODO: Implement RFC 3339 spec in conversion
TIMESTAMP_STRING_CONVERSION_VALID(
"timestamp('2023-01-01T00:00:00Z') == timestamp('2023-01-01T00:00:00Z')"),
DURATION_STRING_CONVERSION_VALID("duration('100s') == duration('100s')"),
BOOL_STRING_UNINTERPRETED("bool('true') == true"),
TIMESTAMP_ADD_DURATION_OVERFLOW("timestamp(253402300799) + duration('100s') > timestamp(0)"),
DYNAMIC_EQUALITY_TIMESTAMP_INT_COLLISION(
"type(dyn_var) == int && dyn_var == 0 ? dyn_var != timestamp('1970-01-01T00:00:00Z') :"
Expand Down
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