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Migration: Remove _ScopedLocalSet class.

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This class wasn't really necessary; it was just a container for a few
extra methods used only by the EdgeBuilder.  By moving those methods
to the EdgeBuilder and removing the _ScopedLocalSet class, we open up
the possibility of expanding the capabilities of those methods to take
advantage of other information the EdgeBuilder has access to.  (I will
do this in follow-up CLs).

No functional change.

Change-Id: I7cf19b8cf81db0413f4a9e747d46fb619d5eac4e
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/206840
Reviewed-by: Konstantin Shcheglov <scheglov@google.com>
Commit-Queue: Paul Berry <paulberry@google.com>
This commit is contained in:
Paul Berry 2021-07-14 17:41:50 +00:00 committed by commit-bot@chromium.org
parent 2591b084d8
commit 054426c9c5
1 changed files with 34 additions and 46 deletions
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80
pkg/nnbd_migration/lib/src/edge_builder.dart
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@ -192,7 +192,7 @@ class EdgeBuilder extends GeneralizingAstVisitor<DecoratedType>
///
/// Note that this is not guaranteed to be complete. It is used to make hard
/// edges on a best-effort basis.
var _postDominatedLocals = _ScopedLocalSet();
var _postDominatedLocals = ScopedSet<Element>();
/// Map whose keys are expressions of the form `a?.b` on the LHS of
/// assignments, and whose values are the nullability nodes corresponding to
@ -242,6 +242,10 @@ class EdgeBuilder extends GeneralizingAstVisitor<DecoratedType>
_whereOrNullTransformer =
WhereOrNullTransformer(typeProvider, _typeSystem);
/// The synthetic element we use as a stand-in for `this` when analyzing
/// extension methods.
Element get _extensionThis => DynamicElementImpl.instance;
/// Gets the decorated type of [element] from [_variables], performing any
/// necessary substitutions.
///
@ -319,7 +323,7 @@ class EdgeBuilder extends GeneralizingAstVisitor<DecoratedType>
source: targetType,
destination: onType,
hard: targetExpression == null ||
_postDominatedLocals.isReferenceInScope(targetExpression));
_isReferenceInScope(targetExpression));
// (3) substitute those decorated types into the declared type of the
// extension method or extension property, so that the caller will match
// up parameter types and the return type appropriately.
@ -507,8 +511,7 @@ class EdgeBuilder extends GeneralizingAstVisitor<DecoratedType>
bool isPure = otherOperand is SimpleIdentifier;
var conditionInfo = _ConditionInfo(node,
isPure: isPure,
postDominatingIntent:
_postDominatedLocals.isReferenceInScope(otherOperand),
postDominatingIntent: _isReferenceInScope(otherOperand),
trueGuard: otherNode,
falseDemonstratesNonNullIntent: otherNode);
_conditionInfo = notEqual ? conditionInfo.not(node) : conditionInfo;
@ -928,7 +931,7 @@ class EdgeBuilder extends GeneralizingAstVisitor<DecoratedType>
_elementsWrittenToInLocalFunction;
try {
_elementsWrittenToInLocalFunction = {};
_postDominatedLocals = _ScopedLocalSet();
_postDominatedLocals = ScopedSet<Element>();
_flowAnalysis!.functionExpression_begin(node);
_dispatch(node.functionExpression);
_flowAnalysis!.functionExpression_end();
@ -993,7 +996,7 @@ class EdgeBuilder extends GeneralizingAstVisitor<DecoratedType>
if (node.parent is! FunctionDeclaration) {
_elementsWrittenToInLocalFunction = {};
}
_postDominatedLocals = _ScopedLocalSet();
_postDominatedLocals = ScopedSet<Element>();
_postDominatedLocals.doScoped(
elements: node.declaredElement!.parameters,
action: () => _dispatch(node.body));
@ -1238,8 +1241,7 @@ class EdgeBuilder extends GeneralizingAstVisitor<DecoratedType>
decoratedType.node, IsCheckMainTypeOrigin(source, type));
_conditionInfo = _ConditionInfo(node,
isPure: expression is SimpleIdentifier,
postDominatingIntent:
_postDominatedLocals.isReferenceInScope(expression),
postDominatingIntent: _isReferenceInScope(expression),
trueDemonstratesNonNullIntent: expressionNode);
if (node.notOperator != null) {
_conditionInfo = _conditionInfo!.not(node);
@ -2061,8 +2063,7 @@ class EdgeBuilder extends GeneralizingAstVisitor<DecoratedType>
// there's nothing to do.
if (_currentExtendedType == null) return;
var origin = ImplicitThisOrigin(source, node);
var hard =
_postDominatedLocals.isInScope(_postDominatedLocals.extensionThis);
var hard = _postDominatedLocals.isInScope(_extensionThis);
_graph.makeNonNullable(thisType!.node, origin, hard: hard, guards: _guards);
}
@ -2329,8 +2330,7 @@ class EdgeBuilder extends GeneralizingAstVisitor<DecoratedType>
callee!.name == 'checkNotNull' &&
node.argumentList.arguments.isNotEmpty) {
var argument = node.argumentList.arguments.first;
if (argument is SimpleIdentifier &&
_postDominatedLocals.isReferenceInScope(argument)) {
if (argument is SimpleIdentifier && _isReferenceInScope(argument)) {
var argumentType =
_variables!.decoratedElementType(argument.staticElement!);
_graph.makeNonNullable(argumentType.node,
@ -2475,8 +2475,7 @@ class EdgeBuilder extends GeneralizingAstVisitor<DecoratedType>
}
}
if (assignmentExpression != null) {
var element = _postDominatedLocals
.referencedElement(assignmentExpression.leftHandSide);
var element = _referencedElement(assignmentExpression.leftHandSide);
if (element != null) {
_postDominatedLocals.removeFromAllScopes(element);
_elementsWrittenToInLocalFunction?.add(element);
@ -2531,7 +2530,7 @@ class EdgeBuilder extends GeneralizingAstVisitor<DecoratedType>
// Push a scope of post-dominated declarations on the stack.
_postDominatedLocals.pushScope(elements: declaredElement.parameters);
if (declaredElement.enclosingElement is ExtensionElement) {
_postDominatedLocals.add(_postDominatedLocals.extensionThis);
_postDominatedLocals.add(_extensionThis);
}
try {
_dispatchList(initializers);
@ -3090,8 +3089,7 @@ class EdgeBuilder extends GeneralizingAstVisitor<DecoratedType>
if (isQuiverCheckNull && node.argumentList.arguments.isNotEmpty) {
var argument = node.argumentList.arguments.first;
if (argument is SimpleIdentifier &&
_postDominatedLocals.isReferenceInScope(argument)) {
if (argument is SimpleIdentifier && _isReferenceInScope(argument)) {
var argumentType =
_variables!.decoratedElementType(argument.staticElement!);
_graph.makeNonNullable(
@ -3147,6 +3145,11 @@ class EdgeBuilder extends GeneralizingAstVisitor<DecoratedType>
bool _isPrefix(Expression? e) =>
e is SimpleIdentifier && e.staticElement is PrefixElement;
bool _isReferenceInScope(Expression expression) {
var element = _referencedElement(expression);
return element != null && _postDominatedLocals.isInScope(element);
}
bool _isUntypedParameter(NormalFormalParameter parameter) {
if (parameter is SimpleFormalParameter) {
return parameter.type == null;
@ -3261,6 +3264,19 @@ class EdgeBuilder extends GeneralizingAstVisitor<DecoratedType>
return node;
}
/// Returns the element referenced directly by [expression], if any; otherwise
/// returns `null`.
Element? _referencedElement(Expression expression) {
expression = expression.unParenthesized;
if (expression is SimpleIdentifier) {
return expression.staticElement;
} else if (expression is ThisExpression || expression is SuperExpression) {
return _extensionThis;
} else {
return null;
}
}
/// Determines whether uses of [expression] should cause hard edges to be
/// created in the nullability graph.
///
@ -3288,8 +3304,7 @@ class EdgeBuilder extends GeneralizingAstVisitor<DecoratedType>
// expression is unconditionally executed, and (b) the expression is a
// reference to a local variable or parameter and it post-dominates the
// declaration of that local variable or parameter.
return !isConditionallyExecuted &&
_postDominatedLocals.isReferenceInScope(expression);
return !isConditionallyExecuted && _isReferenceInScope(expression);
}
DecoratedType? _thisOrSuper(Expression node) {
@ -3772,30 +3787,3 @@ class _ConditionInfo {
trueDemonstratesNonNullIntent: falseDemonstratesNonNullIntent,
falseDemonstratesNonNullIntent: trueDemonstratesNonNullIntent);
}
/// A [ScopedSet] specific to the [Element]s of locals/parameters.
///
/// Contains helpers for dealing with expressions as if they were elements.
class _ScopedLocalSet extends ScopedSet<Element> {
/// The synthetic element we use as a stand-in for `this` when analyzing
/// extension methods.
Element get extensionThis => DynamicElementImpl.instance;
bool isReferenceInScope(Expression expression) {
var element = referencedElement(expression);
return element != null && isInScope(element);
}
/// Returns the element referenced directly by [expression], if any; otherwise
/// returns `null`.
Element? referencedElement(Expression expression) {
expression = expression.unParenthesized;
if (expression is SimpleIdentifier) {
return expression.staticElement;
} else if (expression is ThisExpression || expression is SuperExpression) {
return extensionThis;
} else {
return null;
}
}
}