public void Visit(ReturnNode node)
{
if (node != null)
{
if (node.Operand != null)
{
node.Operand.Accept(this);
}
node.Index = NextOrderIndex;
// we can stop marking order for subsequent statements in this block,
// since this stops execution
m_isUnreachable = true;
}
}
public void Visit(ReturnNode node)
{
// invalid! ignore
IsValid = false;
}
public void Visit(ReturnNode node)
{
// invalid! ignore
IsValid = false;
}
public void Visit(ReturnNode node)
{
Debug.Fail("shouldn't get here");
}
public void Visit(ReturnNode node)
{
// not applicable; terminate
}
public void Visit(ReturnNode node)
{
if (node != null)
{
if (node.Operand != null)
{
node.Operand.Accept(this);
}
node.Index = NextOrderIndex;
// we can stop marking order for subsequent statements in this block,
// since this stops execution
m_isUnreachable = true;
}
}
public void Visit(ReturnNode node)
{
Debug.Fail("shouldn't get here");
}
//---------------------------------------------------------------------------------------
// ParseReturnStatement
//
// ReturnStatement :
// 'return' Expression
//
// This function may return a null AST under error condition. The caller should handle
// that case.
// Regardless of error conditions, on exit the parser points to the first token after
// the return statement.
//---------------------------------------------------------------------------------------
private ReturnNode ParseReturnStatement()
{
var returnNode = new ReturnNode(m_currentToken.Clone(), this);
GetNextToken();
if (!m_foundEndOfLine)
{
if (JSToken.Semicolon != m_currentToken.Token && JSToken.RightCurly != m_currentToken.Token)
{
m_noSkipTokenSet.Add(NoSkipTokenSet.s_EndOfStatementNoSkipTokenSet);
try
{
returnNode.Operand = ParseExpression();
}
catch (RecoveryTokenException exc)
{
returnNode.Operand = exc._partiallyComputedNode;
if (IndexOfToken(NoSkipTokenSet.s_EndOfStatementNoSkipTokenSet, exc) == -1)
{
exc._partiallyComputedNode = returnNode;
throw;
}
}
finally
{
if (returnNode.Operand != null)
{
returnNode.UpdateWith(returnNode.Operand.Context);
}
m_noSkipTokenSet.Remove(NoSkipTokenSet.s_EndOfStatementNoSkipTokenSet);
}
}
if (JSToken.Semicolon == m_currentToken.Token)
{
returnNode.TerminatingContext = m_currentToken.Clone();
GetNextToken();
}
else if (m_foundEndOfLine || m_currentToken.Token == JSToken.RightCurly || m_currentToken.Token == JSToken.EndOfFile)
{
// semicolon insertion rules
// a right-curly or an end of line is something we don't WANT to throw a warning for.
// Just too common and doesn't really warrant a warning (in my opinion)
if (JSToken.RightCurly != m_currentToken.Token && JSToken.EndOfFile != m_currentToken.Token)
{
ReportError(JSError.SemicolonInsertion, returnNode.Context.IfNotNull(c => c.FlattenToEnd()), true);
}
}
else
{
ReportError(JSError.NoSemicolon, false);
}
}
return returnNode;
}
public void Visit(ReturnNode node)
{
// not applicable; terminate
}
private void CombineReturnWithExpression(Block node, int ndx, ReturnNode returnNode)
{
// see if the return node has an expression operand
if (returnNode.Operand != null && returnNode.Operand.IsExpression)
{
// check for lookup[ASSIGN]expr2;return expr1.
var beforeExpr = node[ndx - 1] as BinaryOperator;
Lookup lookup;
if (beforeExpr != null
&& beforeExpr.IsAssign
&& (lookup = beforeExpr.Operand1 as Lookup) != null)
{
if (returnNode.Operand.IsEquivalentTo(lookup))
{
// we have lookup[ASSIGN]expr2;return lookup.
// if lookup is a local variable in the current scope, we can replace with return expr2;
// if lookup is an outer reference, we can replace with return lookup[ASSIGN]expr2
if (beforeExpr.OperatorToken == JSToken.Assign)
{
// check to see if lookup is in the current scope from which we are returning
if (lookup.VariableField == null
|| lookup.VariableField.OuterField != null
|| lookup.VariableField.IsReferencedInnerScope)
{
// transform: lookup[ASSIGN]expr2;return lookup => return lookup[ASSIGN]expr2
// lookup points to outer field (or we don't know)
// replace the operand on the return node with the previous expression and
// delete the previous node.
// first be sure to remove the lookup in the return operand from the references
// to field.
DetachReferences.Apply(returnNode.Operand);
returnNode.Operand = beforeExpr;
node[ndx - 1] = null;
}
else
{
// transform: lookup[ASSIGN]expr2;return lookup => return expr2
// lookup is a variable local to the current scope, so when we return, the
// variable won't exists anymore anyway.
// replace the operand on the return node oprand with the right-hand operand of the
// previous expression and delete the previous node.
// we're eliminating the two lookups altogether, so remove them both from the
// field's reference table.
var varField = lookup.VariableField;
DetachReferences.Apply(lookup, returnNode.Operand);
returnNode.Operand = beforeExpr.Operand2;
node[ndx - 1] = null;
// now that we've eliminated the two lookups, see if the local variable isn't
// referenced anymore. If it isn't, we might be able to remove the variable, too.
// (need to pick up those changes to keep track of a field's declarations, though)
if (varField.RefCount == 0)
{
// it's not. if there's only one declaration and it either has no initializer or
// is initialized to a constant, get rid of it.
var nameDecl = varField.OnlyDeclaration;
if (nameDecl != null)
{
// we only had one declaration.
if (nameDecl.Initializer == null || nameDecl.Initializer.IsConstant)
{
// and it either had no initializer or it was initialized to a constant.
// but it has no references, so let's whack it. Actually, only if it was
// a var-decl (leave parameter and function decls alone).
var varDecl = nameDecl as VariableDeclaration;
if (varDecl != null)
{
// save the declaration parent (var, const, or let) and remove the
// child vardecl from its list
var declStatement = varDecl.Parent as Declaration;
declStatement.Remove(varDecl);
varField.WasRemoved = true;
// if the parent statement is now empty, remove it, too. this will
// move everything up one index, but that'll just mean an extra loop.
if (declStatement.Count == 0)
{
declStatement.Parent.ReplaceChild(declStatement, null);
}
}
}
}
}
}
}
else
{
// it's an assignment, but it's not =. That means it's one of the OP= operators.
// we can't remove the field altogether. But we can move the assignment into the
// return statement and get rid of the lone lookup.
// transform: lookup OP= expr;return lookup => return lookup OP= expr;
if (lookup.VariableField != null)
{
// we're getting rid of the lookup, so remove it from the field's list of references
DetachReferences.Apply(returnNode.Operand);
}
// remove the expression from the block and put it in the operand of
// the return statement.
node.RemoveAt(ndx - 1);
returnNode.Operand = beforeExpr;
// is this field scoped only to this function?
if (lookup.VariableField != null
&& lookup.VariableField.OuterField == null
&& !lookup.VariableField.IsReferencedInnerScope)
{
// in fact, the lookup is in the current scope, so assigning to it is a waste
// because we're going to return (this is a return statement, after all).
// we can get rid of the assignment part and just keep the operator:
// transform: lookup OP= expr;return lookup => return lookup OP expr;
beforeExpr.OperatorToken = JSScanner.StripAssignment(beforeExpr.OperatorToken);
}
}
}
else
{
// transform: expr1;return expr2 to return expr1,expr2
var binOp = CommaOperator.CombineWithComma(null, m_parser, node[ndx - 1], returnNode.Operand);
// replace the operand on the return node with the new expression and
// delete the previous node
returnNode.Operand = binOp;
node[ndx - 1] = null;
}
}
else
{
// transform: expr1;return expr2 to return expr1,expr2
var binOp = CommaOperator.CombineWithComma(null, m_parser, node[ndx - 1], returnNode.Operand);
// replace the operand on the return node with the new expression and
// delete the previous node
returnNode.Operand = binOp;
node[ndx - 1] = null;
}
}
}
public override void Visit(ReturnNode node)
{
if (node != null)
{
// first we want to make sure that we are indeed within a function scope.
// it makes no sense to have a return outside of a function
ActivationObject scope = m_scopeStack.Peek();
while (scope != null && !(scope is FunctionScope))
{
scope = scope.Parent;
}
if (scope == null)
{
node.Context.HandleError(JSError.BadReturn);
}
// recurse the operand if we have one
if (node.Operand != null)
{
node.Operand.Accept(this);
// now see if it's a binary op assignment to a variable local to this scope.
// if it is, we can get rid of the assignment because we're leaving the scope.
var lookup = node.Operand.LeftHandSide as Lookup;
BinaryOperator binaryOp;
if (lookup != null
&& lookup.VariableField != null
&& lookup.VariableField.OuterField == null
&& (binaryOp = lookup.Parent as BinaryOperator) != null
&& binaryOp.IsAssign
&& !lookup.VariableField.IsReferencedInnerScope)
{
if (binaryOp.OperatorToken != JSToken.Assign)
{
// it's an OP= assignment, so keep the lookup, but convert the operator to a non-assignment
binaryOp.OperatorToken = JSScanner.StripAssignment(binaryOp.OperatorToken);
}
else if (binaryOp.Parent == node)
{
// straight assignment. But we can only get rid of the assignment if
// it's the root operation of the return. If it's buried down in a complex
// assignment, then leave it be.
lookup.VariableField.References.Remove(lookup);
node.Operand = binaryOp.Operand2;
}
}
}
}
}
public override void Visit(IfNode node)
{
if (node != null)
{
if (m_parser.Settings.StripDebugStatements
&& m_parser.Settings.IsModificationAllowed(TreeModifications.StripDebugStatements))
{
if (node.TrueBlock != null && node.TrueBlock.IsDebuggerStatement)
{
node.TrueBlock = null;
}
if (node.FalseBlock != null && node.FalseBlock.IsDebuggerStatement)
{
node.FalseBlock = null;
}
}
// recurse....
base.Visit(node);
// now check to see if the two branches are now empty.
// if they are, null them out.
if (node.TrueBlock != null && node.TrueBlock.Count == 0)
{
node.TrueBlock = null;
}
if (node.FalseBlock != null && node.FalseBlock.Count == 0)
{
node.FalseBlock = null;
}
if (node.TrueBlock != null && node.FalseBlock != null)
{
// neither true block nor false block is null.
// if they're both expressions, convert them to a condition operator
if (node.TrueBlock.IsExpression && node.FalseBlock.IsExpression
&& m_parser.Settings.IsModificationAllowed(TreeModifications.IfExpressionsToExpression))
{
// if this statement has both true and false blocks, and they are both expressions,
// then we can simplify this to a conditional expression.
// because the blocks are expressions, we know they only have ONE statement in them,
// so we can just dereference them directly.
Conditional conditional;
var logicalNot = new LogicalNot(node.Condition, m_parser);
if (logicalNot.Measure() < 0)
{
// applying a logical-not makes the condition smaller -- reverse the branches
logicalNot.Apply();
conditional = new Conditional(node.Context, m_parser)
{
Condition = node.Condition,
TrueExpression = node.FalseBlock[0],
FalseExpression = node.TrueBlock[0]
};
}
else
{
// regular order
conditional = new Conditional(node.Context, m_parser)
{
Condition = node.Condition,
TrueExpression = node.TrueBlock[0],
FalseExpression = node.FalseBlock[0]
};
}
node.Parent.ReplaceChild(
node,
conditional);
Optimize(conditional);
}
else
{
// see if logical-notting the condition produces something smaller
var logicalNot = new LogicalNot(node.Condition, m_parser);
if (logicalNot.Measure() < 0)
{
// it does -- not the condition and swap the branches
logicalNot.Apply();
node.SwapBranches();
}
// see if the true- and false-branches each contain only a single statement
if (node.TrueBlock.Count == 1 && node.FalseBlock.Count == 1)
{
// they do -- see if the true-branch's statement is a return-statement
var trueReturn = node.TrueBlock[0] as ReturnNode;
if (trueReturn != null && trueReturn.Operand != null)
{
// it is -- see if the false-branch is also a return statement
var falseReturn = node.FalseBlock[0] as ReturnNode;
if (falseReturn != null && falseReturn.Operand != null)
{
// transform: if(cond)return expr1;else return expr2 to return cond?expr1:expr2
var conditional = new Conditional(null, m_parser)
{
Condition = node.Condition,
TrueExpression = trueReturn.Operand,
FalseExpression = falseReturn.Operand
};
// create a new return node from the conditional and replace
// our if-node with it
var returnNode = new ReturnNode(node.Context, m_parser)
{
Operand = conditional
};
node.Parent.ReplaceChild(
node,
returnNode);
Optimize(conditional);
}
}
}
}
}
else if (node.FalseBlock != null)
{
// true block must be null.
// if there is no true branch but a false branch, then
// put a not on the condition and move the false branch to the true branch.
if (node.FalseBlock.IsExpression
&& m_parser.Settings.IsModificationAllowed(TreeModifications.IfConditionCallToConditionAndCall))
{
// if (cond); else expr ==> cond || expr
// but first -- which operator to use? if(a);else b --> a||b, and if(!a);else b --> a&&b
// so determine which one is smaller: a or !a
// assume we'll use the logical-or, since that doesn't require changing the condition
var newOperator = JSToken.LogicalOr;
var logicalNot = new LogicalNot(node.Condition, m_parser);
if (logicalNot.Measure() < 0)
{
// !a is smaller, so apply it and use the logical-or operator
logicalNot.Apply();
newOperator = JSToken.LogicalAnd;
}
var binaryOp = new BinaryOperator(node.Context, m_parser)
{
Operand1 = node.Condition,
Operand2 = node.FalseBlock[0],
OperatorToken = newOperator,
};
// we don't need to analyse this new node because we've already analyzed
// the pieces parts as part of the if. And this visitor's method for the BinaryOperator
// doesn't really do anything else. Just replace our current node with this
// new node
node.Parent.ReplaceChild(node, binaryOp);
}
else if (m_parser.Settings.IsModificationAllowed(TreeModifications.IfConditionFalseToIfNotConditionTrue))
{
// logical-not the condition
// if(cond);else stmt ==> if(!cond)stmt
var logicalNot = new LogicalNot(node.Condition, m_parser);
logicalNot.Apply();
// and swap the branches
node.SwapBranches();
}
}
else if (node.TrueBlock != null)
{
// false block must be null
if (node.TrueBlock.IsExpression
&& m_parser.Settings.IsModificationAllowed(TreeModifications.IfConditionCallToConditionAndCall))
{
// convert the if-node to an expression
IfConditionExpressionToExpression(node, node.TrueBlock[0]);
}
}
else if (m_parser.Settings.IsModificationAllowed(TreeModifications.IfEmptyToExpression))
{
// NEITHER branches have anything now!
// as long as the condition doesn't
// contain calls or assignments, we should be able to completely delete
// the statement altogether rather than changing it to an expression
// statement on the condition.
// but how do we KNOW there are no side-effects?
// if the condition is a constant or operations on constants, delete it.
// or if the condition itself is a debugger statement -- a call, lookup, or member.
var remove = node.Condition.IsConstant || node.Condition.IsDebuggerStatement;
if (remove)
{
// we're pretty sure there are no side-effects; remove it altogether
node.Parent.ReplaceChild(node, null);
}
else
{
// We don't know what it is and what the side-effects may be, so
// just change this statement into an expression statement by replacing us with
// the expression
// no need to analyze -- we already recursed
node.Parent.ReplaceChild(node, node.Condition);
}
}
if (node.FalseBlock == null
&& node.TrueBlock != null
&& node.TrueBlock.Count == 1
&& m_parser.Settings.IsModificationAllowed(TreeModifications.CombineNestedIfs))
{
var nestedIf = node.TrueBlock[0] as IfNode;
if (nestedIf != null && nestedIf.FalseBlock == null)
{
// we have nested if-blocks.
// transform if(cond1)if(cond2){...} to if(cond1&&cond2){...}
// change the first if-statement's condition to be cond1&&cond2
// move the nested if-statement's true block to the outer if-statement
node.Condition = new BinaryOperator(null, m_parser)
{
Operand1 = node.Condition,
Operand2 = nestedIf.Condition,
OperatorToken = JSToken.LogicalAnd
};
node.TrueBlock = nestedIf.TrueBlock;
}
}
}
}
