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[CFE] Fail silently on invalid constructs during constant evaluation.
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This acts as a stable backstop for situations where Fasta fails to
rewrite various erroneous constructs into invalid expressions.

Change-Id: Ibaac3d62b9cfdc597c0f85aadf9aec2920689222
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/97511
Reviewed-by: Kevin Millikin <kmillikin@google.com>
Commit-Queue: Aske Simon Christensen <askesc@google.com>
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@askeksa
askeksa authored and commit-bot@chromium.org committed Mar 26, 2019
1 parent a8e51c5 commit 4c48062
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Showing 4 changed files with 86 additions and 24 deletions.
32 changes: 32 additions & 0 deletions pkg/front_end/lib/src/fasta/fasta_codes_generated.dart
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Original file line number Diff line number Diff line change
Expand Up @@ -1214,6 +1214,38 @@ Message _withArgumentsConstEvalInvalidMethodInvocation(
arguments: {'string': string, 'constant': _constant});
}

// DO NOT EDIT. THIS FILE IS GENERATED. SEE TOP OF FILE.
const Template<
Message Function(
String string,
Constant
_constant)> templateConstEvalInvalidPropertyGet = const Template<
Message Function(String string, Constant _constant)>(
messageTemplate:
r"""The property '#string' can't be accessed on '#constant' within a const context.""",
withArguments: _withArgumentsConstEvalInvalidPropertyGet);

// DO NOT EDIT. THIS FILE IS GENERATED. SEE TOP OF FILE.
const Code<Message Function(String string, Constant _constant)>
codeConstEvalInvalidPropertyGet =
const Code<Message Function(String string, Constant _constant)>(
"ConstEvalInvalidPropertyGet", templateConstEvalInvalidPropertyGet,
analyzerCodes: <String>["CONST_EVAL_THROWS_EXCEPTION"]);

// DO NOT EDIT. THIS FILE IS GENERATED. SEE TOP OF FILE.
Message _withArgumentsConstEvalInvalidPropertyGet(
String string, Constant _constant) {
if (string.isEmpty) throw 'No string provided';
TypeLabeler labeler = new TypeLabeler();
List<Object> constantParts = labeler.labelConstant(_constant);
String constant = constantParts.join();
return new Message(codeConstEvalInvalidPropertyGet,
message:
"""The property '${string}' can't be accessed on '${constant}' within a const context.""" +
labeler.originMessages,
arguments: {'string': string, 'constant': _constant});
}

// DO NOT EDIT. THIS FILE IS GENERATED. SEE TOP OF FILE.
const Template<
Message Function(
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73 changes: 49 additions & 24 deletions pkg/front_end/lib/src/fasta/kernel/constant_evaluator.dart
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Original file line number Diff line number Diff line change
Expand Up @@ -48,6 +48,7 @@ import '../fasta_codes.dart'
templateConstEvalInvalidType,
templateConstEvalInvalidBinaryOperandType,
templateConstEvalInvalidMethodInvocation,
templateConstEvalInvalidPropertyGet,
templateConstEvalInvalidStaticInvocation,
templateConstEvalInvalidStringInterpolationOperand,
templateConstEvalInvalidSymbolName,
Expand Down Expand Up @@ -478,17 +479,27 @@ class ConstantEvaluator extends RecursiveVisitor<Constant> {
errorReporter.report(locatedMessage, contextMessages);
return new UnevaluatedConstant(new InvalidExpression(e.message.message));
} on _AbortDueToInvalidExpression catch (e) {
errorReporter.reportInvalidExpression(e.node);
return new UnevaluatedConstant(e.node);
// TODO(askesc): Copy position from erroneous node.
// Currently not possible, as it might be in a different file.
// Can be done if we add an explicit URI to InvalidExpression.
InvalidExpression invalid = new InvalidExpression(e.message);
if (invalid.fileOffset == TreeNode.noOffset) {
invalid.fileOffset = node.fileOffset;
}
errorReporter.reportInvalidExpression(invalid);
return new UnevaluatedConstant(invalid);
}
}

/// Report an error that has been detected during constant evaluation.
Null report(TreeNode node, Message message, {List<LocatedMessage> context}) {
throw new _AbortDueToError(node, message, context: context);
}

Null reportInvalidExpression(InvalidExpression node) {
throw new _AbortDueToInvalidExpression(node);
/// Report a construct that should not occur inside a potentially constant
/// expression. It is assumed that an error has already been reported.
Null reportInvalid(TreeNode node, String message) {
throw new _AbortDueToInvalidExpression(node, message);
}

/// Produce an unevaluated constant node for an expression.
Expand Down Expand Up @@ -575,7 +586,8 @@ class ConstantEvaluator extends RecursiveVisitor<Constant> {
defaultTreeNode(Node node) {
// Only a subset of the expression language is valid for constant
// evaluation.
throw 'Constant evaluation has no support for ${node.runtimeType} yet!';
return reportInvalid(
node, 'Constant evaluation has no support for ${node.runtimeType}!');
}

visitNullLiteral(NullLiteral node) => nullConstant;
Expand Down Expand Up @@ -707,15 +719,18 @@ class ConstantEvaluator extends RecursiveVisitor<Constant> {
final Constructor constructor = node.target;
final Class klass = constructor.enclosingClass;
if (!constructor.isConst) {
throw 'The front-end should ensure we do not encounter a '
'constructor invocation of a non-const constructor.';
return reportInvalid(node, 'Non-const constructor invocation.');
}
if (constructor.function.body != null &&
constructor.function.body is! EmptyStatement) {
throw 'Constructor "$node" has non-trivial body "${constructor.function.body.runtimeType}".';
return reportInvalid(
node,
'Constructor "$node" has non-trivial body '
'"${constructor.function.body.runtimeType}".');
}
if (klass.isAbstract) {
throw 'Constructor "$node" belongs to abstract class "${klass}".';
return reportInvalid(
node, 'Constructor "$node" belongs to abstract class "${klass}".');
}

final positionals = evaluatePositionalArguments(node.arguments);
Expand Down Expand Up @@ -993,16 +1008,18 @@ class ConstantEvaluator extends RecursiveVisitor<Constant> {
}
}
} else {
throw new Exception(
'No support for handling initializer of type "${init.runtimeType}".');
return reportInvalid(
constructor,
'No support for handling initializer of type '
'"${init.runtimeType}".');
}
}
});
});
}

visitInvalidExpression(InvalidExpression node) {
return reportInvalidExpression(node);
return reportInvalid(node, node.message);
}

visitMethodInvocation(MethodInvocation node) {
Expand Down Expand Up @@ -1260,12 +1277,16 @@ class ConstantEvaluator extends RecursiveVisitor<Constant> {
visitPropertyGet(PropertyGet node) {
if (node.receiver is ThisExpression) {
// Access "this" during instance creation.
if (instanceBuilder == null) {
return reportInvalid(node, 'Instance field access outside constructor');
}
for (final Field field in instanceBuilder.fields.keys) {
if (field.name == node.name) {
return instanceBuilder.fields[field];
}
}
throw 'Could not evaluate field get ${node.name} on incomplete instance';
return reportInvalid(node,
'Could not evaluate field get ${node.name} on incomplete instance');
}

final Constant receiver = _evaluateSubexpression(node.receiver);
Expand All @@ -1283,7 +1304,10 @@ class ConstantEvaluator extends RecursiveVisitor<Constant> {
} else if (receiver is NullConstant) {
return report(node, messageConstEvalNullValue);
}
throw 'Could not evaluate property get on $receiver.';
return report(
node,
templateConstEvalInvalidPropertyGet.withArguments(
node.name.name, receiver));
}

visitLet(Let node) {
Expand All @@ -1310,8 +1334,7 @@ class ConstantEvaluator extends RecursiveVisitor<Constant> {
if (variable.isConst) {
return _evaluateSubexpression(variable.initializer);
}
throw new Exception('The front-end should ensure we do not encounter a '
'variable get of a non-const variable.');
return reportInvalid(node, 'Variable get of a non-const variable.');
}

visitStaticGet(StaticGet node) {
Expand Down Expand Up @@ -1340,8 +1363,8 @@ class ConstantEvaluator extends RecursiveVisitor<Constant> {
templateConstEvalInvalidStaticInvocation
.withArguments(target.name.name));
} else {
throw new Exception(
'No support for ${target.runtimeType} in a static-get.');
reportInvalid(
node, 'No support for ${target.runtimeType} in a static-get.');
}
});
}
Expand Down Expand Up @@ -1530,14 +1553,15 @@ class ConstantEvaluator extends RecursiveVisitor<Constant> {
return canonicalize(
new PartialInstantiationConstant(constant, typeArguments));
}
throw new Exception(
return reportInvalid(
node,
'The number of type arguments supplied in the partial instantiation '
'does not match the number of type arguments of the $constant.');
}
// The inner expression in an instantiation can never be null, since
// instantiations are only inferred on direct references to declarations.
throw new Exception(
'Only tear-off constants can be partially instantiated.');
return reportInvalid(
node, 'Only tear-off constants can be partially instantiated.');
}

@override
Expand Down Expand Up @@ -1701,7 +1725,7 @@ class ConstantEvaluator extends RecursiveVisitor<Constant> {
return a > b ? trueConstant : falseConstant;
}

throw new Exception("Unexpected binary numeric operation '$op'.");
return reportInvalid(node, "Unexpected binary numeric operation '$op'.");
}

Library libraryOf(TreeNode node) {
Expand Down Expand Up @@ -1793,9 +1817,10 @@ class _AbortDueToError {
}

class _AbortDueToInvalidExpression {
final InvalidExpression node;
final TreeNode node;
final String message;

_AbortDueToInvalidExpression(this.node);
_AbortDueToInvalidExpression(this.node, this.message);
}

abstract class ErrorReporter {
Expand Down
1 change: 1 addition & 0 deletions pkg/front_end/messages.status
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Original file line number Diff line number Diff line change
Expand Up @@ -72,6 +72,7 @@ ConstEvalFreeTypeParameter/example: Fail
ConstEvalInvalidBinaryOperandType/analyzerCode: Fail # CONST_EVAL_TYPE_NUM / CONST_EVAL_TYPE_BOOL
ConstEvalInvalidBinaryOperandType/example: Fail
ConstEvalInvalidMethodInvocation/example: Fail
ConstEvalInvalidPropertyGet/example: Fail
ConstEvalInvalidStaticInvocation/example: Fail
ConstEvalInvalidStringInterpolationOperand/example: Fail
ConstEvalInvalidSymbolName/example: Fail
Expand Down
4 changes: 4 additions & 0 deletions pkg/front_end/messages.yaml
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Original file line number Diff line number Diff line change
Expand Up @@ -110,6 +110,10 @@ ConstEvalInvalidMethodInvocation:
template: "The method '#string' can't be invoked on '#constant' within a const context."
analyzerCode: UNDEFINED_OPERATOR

ConstEvalInvalidPropertyGet:
template: "The property '#string' can't be accessed on '#constant' within a const context."
analyzerCode: CONST_EVAL_THROWS_EXCEPTION

ConstEvalInvalidStringInterpolationOperand:
template: "The '#constant' can't be used as part of a string interpolation within a const context, only values of type 'null', 'bool', 'int', 'double', or 'String' can be used."
analyzerCode: CONST_EVAL_TYPE_BOOL_NUM_STRING
Expand Down

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