public static void Apply(AstNode node, JSParser parser)
{
var logicalNot = new LogicalNot(node, parser);
logicalNot.Apply();
}
public override void Visit(Conditional node)
{
if (node != null)
{
// we have two choices for the conditional. Either:
// 1. we wrap the whole thing in a logical-not operator, which means we also need to
// add parentheses, since conditional is lower-precedence than the logicial not, or
// 2. apply the logical-not to both the true- and false-branches.
// The first is guaranteed 3 additional characters. We have to check the delta for
// each branch and add them together to know how much the second would cost. If it's
// greater than 3, then we just want to not the whole thing.
var notTrue = new LogicalNot(node.TrueExpression, m_parser);
var notFalse = new LogicalNot(node.FalseExpression, m_parser);
var costNottingBoth = notTrue.Measure() + notFalse.Measure();
if (m_measure)
{
// we're just measuring -- adjust the delta accordingly
// (the lesser of the two options)
m_delta += (costNottingBoth > 3) ? 3 : costNottingBoth;
}
else if (costNottingBoth > 3)
{
// just wrap the whole thing
WrapWithLogicalNot(node);
}
else
{
// less bytes to wrap each branch separately
node.TrueExpression.Accept(this);
node.FalseExpression.Accept(this);
}
}
}
public override void Visit(Block node)
{
if (node != null)
{
// if this block has a block scope, then look at the lexically-declared names (if any)
// and throw an error if any are defined as var's within this scope (ES6 rules).
// if this is the body of a function object, use the function scope.
ActivationObject lexicalScope = node.BlockScope;
if (lexicalScope == null)
{
var functionObject = node.Parent as FunctionObject;
if (functionObject != null)
{
lexicalScope = functionObject.FunctionScope;
}
}
if (lexicalScope != null)
{
foreach (var lexDecl in lexicalScope.LexicallyDeclaredNames)
{
var varDecl = lexicalScope.VarDeclaredName(lexDecl.Name);
if (varDecl != null)
{
// collision.
// if the lexical declaration is a let or const declaration (as opposed to a function declaration),
// then force the warning to an error. This is so the function declaration will remain a warning if
// it collides with a var.
varDecl.NameContext.HandleError(JSError.DuplicateLexicalDeclaration, lexDecl is LexicalDeclaration);
// mark them both a no-rename to preserve the collision in the output
lexDecl.VariableField.IfNotNull(v => v.CanCrunch = false);
varDecl.VariableField.IfNotNull(v => v.CanCrunch = false);
}
}
}
// we might things differently if these statements are the body collection for a function
// because we can assume the implicit return statement at the end of it
bool isFunctionLevel = (node.Parent is FunctionObject);
// if we want to remove debug statements...
if (m_parser.Settings.StripDebugStatements && m_parser.Settings.IsModificationAllowed(TreeModifications.StripDebugStatements))
{
// do it now before we try doing other things
StripDebugStatements(node);
}
// analyze all the statements in our block and recurse them
if (node.BlockScope != null)
{
m_scopeStack.Push(node.BlockScope);
}
try
{
// don't call the base class to recurse -- let's walk the block
// backwards in case any of the children opt to delete themselves.
for (var ndx = node.Count - 1; ndx >= 0; --ndx)
{
node[ndx].Accept(this);
}
}
finally
{
if (node.BlockScope != null)
{
m_scopeStack.Pop();
}
}
if (m_parser.Settings.RemoveUnneededCode)
{
// go forward, and check the count each iteration because we might be ADDING statements to the block.
// let's look at all our if-statements. If a true-clause ends in a return, then we don't
// need the else-clause; we can pull its statements out and stick them after the if-statement.
// also, if we encounter a return-, break- or continue-statement, we can axe everything after it
for (var ndx = 0; ndx < node.Count; ++ndx)
{
// see if it's an if-statement with both a true and a false block
var ifNode = node[ndx] as IfNode;
if (ifNode != null
&& ifNode.TrueBlock != null
&& ifNode.TrueBlock.Count > 0
&& ifNode.FalseBlock != null)
{
// now check to see if the true block ends in a return statement
if (ifNode.TrueBlock[ifNode.TrueBlock.Count - 1] is ReturnNode)
{
// transform: if(cond){statements1;return}else{statements2} to if(cond){statements1;return}statements2
// it does. insert all the false-block statements after the if-statement
node.InsertRange(ndx + 1, ifNode.FalseBlock.Children);
// and then remove the false block altogether
ifNode.FalseBlock = null;
}
}
else if (node[ndx] is ReturnNode
|| node[ndx] is Break
|| node[ndx] is ContinueNode
|| node[ndx] is ThrowNode)
{
// we have an exit node -- no statments afterwards will be executed, so clear them out.
// transform: {...;return;...} to {...;return}
// transform: {...;break;...} to {...;break}
// transform: {...;continue;...} to {...;continue}
// transform: {...;throw;...} to {...;throw}
// we've found an exit statement, and it's not the last statement in the function.
// walk the rest of the statements and delete anything that isn't a function declaration
// or a var- or const-statement.
for (var ndxRemove = node.Count - 1; ndxRemove > ndx; --ndxRemove)
{
var funcObject = node[ndxRemove] as FunctionObject;
if (funcObject == null || funcObject.FunctionType != FunctionType.Declaration)
{
// if it's a const-statement, leave it.
// we COULD check to see if the constant is referenced anywhere and delete
// any that aren't. Maybe later.
// we also don't want to do like the var-statements and remove the initializers.
// Not sure if any browsers would fail a const WITHOUT an initializer.
if (!(node[ndxRemove] is ConstStatement))
{
var varStatement = node[ndxRemove] as Var;
if (varStatement != null)
{
// var statements can't be removed, but any initializers should
// be deleted since they won't get executed.
for (var ndxDecl = 0; ndxDecl < varStatement.Count; ++ndxDecl)
{
if (varStatement[ndxDecl].Initializer != null)
{
varStatement[ndxDecl].Initializer = null;
}
}
}
else
{
// not a function declaration, and not a var statement -- get rid of it
DetachReferences.Apply(node[ndxRemove]);
node.RemoveAt(ndxRemove);
}
}
}
}
}
}
}
// now check the last statement -- if it's an if-statement where the true-block is a single return
// and there is no false block, convert this one statement to a conditional. We might back it out later
// if we don't combine the conditional with other stuff.
// but we can only do this if we're at the functional level because of the implied return at the end
// of that block.
if (isFunctionLevel && node.Count > 0
&& m_parser.Settings.IsModificationAllowed(TreeModifications.IfConditionReturnToCondition))
{
ReturnNode returnNode;
var ifNode = FindLastStatement(node) as IfNode;
if (ifNode != null && ifNode.FalseBlock == null
&& ifNode.TrueBlock.Count == 1
&& (returnNode = ifNode.TrueBlock[0] as ReturnNode) != null)
{
// if the return node doesn't have an operand, then we can just replace the if-statement with its conditional
if (returnNode.Operand == null)
{
// if the condition is a constant, then eliminate it altogether
if (ifNode.Condition.IsConstant)
{
// delete the node altogether. Because the condition is a constant,
// there is no else-block, and the if-block only contains a return
// with no expression, we don't have anything to detach.
node.ReplaceChild(ifNode, null);
}
else
{
// transform: {...;if(cond)return;} to {...;cond;}
node.ReplaceChild(ifNode, ifNode.Condition);
}
}
else if (returnNode.Operand.IsExpression)
{
// this is a strategic replacement that might pay off later. And if
// it doesn't, we'll eventually back it out after all the other stuff
// if applied on top of it.
// transform: if(cond)return expr;} to return cond?expr:void 0}
var conditional = new Conditional(null, m_parser)
{
Condition = ifNode.Condition,
TrueExpression = returnNode.Operand,
FalseExpression = CreateVoidNode()
};
// replace the if-statement with the new return node
node.ReplaceChild(ifNode, new ReturnNode(ifNode.Context, m_parser)
{
Operand = conditional
});
Optimize(conditional);
}
}
}
// now walk through and combine adjacent expression statements, and adjacent var-for statements
// and adjecent expression-return statements
if (m_parser.Settings.IsModificationAllowed(TreeModifications.CombineAdjacentExpressionStatements))
{
CombineExpressions(node);
}
// check to see if we want to combine a preceding var with a for-statement
if (m_parser.Settings.IsModificationAllowed(TreeModifications.MoveVarIntoFor))
{
// look at the statements in the block.
// walk BACKWARDS down the list because we'll be removing items when we encounter
// var statements that can be moved inside a for statement's initializer
// we also don't need to check the first one, since there is nothing before it.
for (int ndx = node.Count - 1; ndx > 0; --ndx)
{
// see if the previous statement is a var statement
// (we've already combined adjacent var-statements)
ForNode forNode;
WhileNode whileNode;
var previousVar = node[ndx - 1] as Var;
if (previousVar != null && (forNode = node[ndx] as ForNode) != null)
{
// BUT if the var statement has any initializers containing an in-operator, first check
// to see if we haven't killed that move before we try moving it. Opera 11 seems to have
// an issue with that syntax, even if properly parenthesized.
if (m_parser.Settings.IsModificationAllowed(TreeModifications.MoveInExpressionsIntoForStatement)
|| !previousVar.ContainsInOperator)
{
// and see if the forNode's initializer is empty
if (forNode.Initializer != null)
{
// not empty -- see if it is a Var node
Var varInitializer = forNode.Initializer as Var;
if (varInitializer != null)
{
// transform: var decls1;for(var decls2;...) to for(var decls1,decls2;...)
// we want to PREPEND the initializers in the previous var-statement
// to our for-statement's initializer var-statement list
varInitializer.InsertAt(0, previousVar);
// then remove the previous var statement
node.RemoveAt(ndx - 1);
// this will bump the for node up one position in the list, so the next iteration
// will be right back on this node in case there are other var statements we need
// to combine
}
else
{
// we want to see if the initializer expression is a series of one or more
// simple assignments to variables that are in the previous var statement.
// if all the expressions are assignments to variables that are defined in the
// previous var statement, then we can just move the var statement into the
// for statement.
var binaryOp = forNode.Initializer as BinaryOperator;
if (binaryOp != null && AreAssignmentsInVar(binaryOp, previousVar))
{
// transform: var decls;for(expr1;...) to for(var decls,expr1;...)
// WHERE expr1 only consists of assignments to variables that are declared
// in that previous var-statement.
// TODO: we *could* also do it is the expr1 assignments are to lookups that are
// defined in THIS scope (not any outer scopes), because it wouldn't hurt to have
// then in a var statement again.
// create a list and fill it with all the var-decls created from the assignment
// operators in the expression
var varDecls = new List<VariableDeclaration>();
ConvertAssignmentsToVarDecls(binaryOp, varDecls, m_parser);
// then go through and append each one to the var statement before us
foreach (var varDecl in varDecls)
{
previousVar.Append(varDecl);
}
// move the previous var-statement into our initializer
forNode.Initializer = previousVar;
// and remove the previous var-statement from the list.
node.RemoveAt(ndx - 1);
// this will bump the for node up one position in the list, so the next iteration
// will be right back on this node, but the initializer will not be null
}
}
}
else
{
// transform: var decls;for(;...) to for(var decls;...)
// if it's empty, then we're free to add the previous var statement
// to this for statement's initializer. remove it from it's current
// position and add it as the initializer
node.RemoveAt(ndx - 1);
forNode.Initializer = previousVar;
// this will bump the for node up one position in the list, so the next iteration
// will be right back on this node, but the initializer will not be null
}
}
}
else if (previousVar != null
&& (whileNode = node[ndx] as WhileNode) != null
&& m_parser.Settings.IsModificationAllowed(TreeModifications.ChangeWhileToFor))
{
// transform: var ...;while(cond)... => for(var ...;cond;)...
node[ndx] = new ForNode(null, m_parser)
{
Initializer = previousVar,
Condition = whileNode.Condition,
Body = whileNode.Body
};
node.RemoveAt(ndx - 1);
}
}
}
// see if the last statement is a return statement
ReturnNode lastReturn;
if ((lastReturn = FindLastStatement(node) as ReturnNode) != null)
{
// set this flag to true if we end up adding an expression to the block.
// before exiting, we'll go through and combine adjacent expressions again if this
// flag has been set to true.
bool changedStatementToExpression = false;
// get the index of the statement before the last return
// (skip over function decls and importand comments)
var indexPrevious = PreviousStatementIndex(node, lastReturn);
// just out of curiosity, let's see if we fit a common pattern:
// var name=expr;return name;
// or
// const name=expr;return name;
// if so, we can cut out the var and simply return the expression
Lookup lookup;
if ((lookup = lastReturn.Operand as Lookup) != null && indexPrevious >= 0)
{
// use the base class for both the var- and const-statements so we will
// pick them both up at the same time
var varStatement = node[indexPrevious] as Declaration;
if (varStatement != null)
{
// if the last vardecl in the var statement matches the return lookup, and no
// other references exist for this field (refcount == 1)...
VariableDeclaration varDecl;
if ((varDecl = varStatement[varStatement.Count - 1]).Initializer != null
&& varDecl.IsEquivalentTo(lookup)
&& varDecl.VariableField.RefCount == 1)
{
// clean up the field's references because we're removing both the lookup reference
// in the return statement and the vardecl.
varDecl.VariableField.References.Remove(lookup);
varDecl.VariableField.Declarations.Remove(varDecl);
if (varStatement.Count == 1)
{
// transform: ...;var name=expr;return name} to ...;return expr}
// there's only one vardecl in the var, so get rid of the entire statement
lastReturn.Operand = varDecl.Initializer;
node.RemoveAt(indexPrevious);
}
else
{
// multiple vardecls are in the statement; we only need to get rid of the last one
lastReturn.Operand = varDecl.Initializer;
varStatement[varStatement.Count - 1] = null;
}
}
}
}
// check to see if we can combine the return statement with a previous if-statement
// into a simple return-conditional. The true statement needs to have no false block,
// and only one statement in the true block.
Conditional conditional;
IfNode previousIf;
while (indexPrevious >= 0
&& lastReturn != null
&& (previousIf = node[indexPrevious] as IfNode) != null
&& previousIf.TrueBlock != null && previousIf.TrueBlock.Count == 1
&& previousIf.FalseBlock == null)
{
// assume no change is made for this loop
bool somethingChanged = false;
// and that one true-block statement needs to be a return statement
var previousReturn = previousIf.TrueBlock[0] as ReturnNode;
if (previousReturn != null)
{
if (lastReturn.Operand == null)
{
if (previousReturn.Operand == null)
{
// IF we are at the function level, then the block ends in an implicit return (undefined)
// and we can change this if to just the condition. If we aren't at the function level,
// then we have to leave the return, but we can replace the if with just the condition.
if (!isFunctionLevel)
{
// not at the function level, so the return must stay.
if (previousIf.Condition.IsConstant)
{
// transform: if(cond)return;return} to return}
node.RemoveAt(indexPrevious);
somethingChanged = true;
}
else
{
// transform: if(cond)return;return} to cond;return}
node[indexPrevious] = previousIf.Condition;
}
}
else if (previousIf.Condition.IsConstant)
{
// transform: remove if(cond)return;return} because cond is a constant
node.ReplaceChild(lastReturn, null);
node.RemoveAt(indexPrevious);
somethingChanged = true;
}
else
{
// transform: if(cond)return;return} to cond}
// replace the final return with just the condition, then remove the previous if
if (node.ReplaceChild(lastReturn, previousIf.Condition))
{
node.RemoveAt(indexPrevious);
somethingChanged = true;
}
}
}
else
{
// transform: if(cond)return expr;return} to return cond?expr:void 0
conditional = new Conditional(null, m_parser)
{
Condition = previousIf.Condition,
TrueExpression = previousReturn.Operand,
FalseExpression = CreateVoidNode()
};
// replace the final return with the new return, then delete the previous if-statement
if (node.ReplaceChild(lastReturn, new ReturnNode(null, m_parser)
{
Operand = conditional
}))
{
node.RemoveAt(indexPrevious);
Optimize(conditional);
somethingChanged = true;
}
}
}
else
{
if (previousReturn.Operand == null)
{
// transform: if(cond)return;return expr} to return cond?void 0:expr
conditional = new Conditional(null, m_parser)
{
Condition = previousIf.Condition,
TrueExpression = CreateVoidNode(),
FalseExpression = lastReturn.Operand
};
// replace the final return with the new return, then delete the previous if-statement
if (node.ReplaceChild(lastReturn, new ReturnNode(null, m_parser)
{
Operand = conditional
}))
{
node.RemoveAt(indexPrevious);
Optimize(conditional);
somethingChanged = true;
}
}
else if (previousReturn.Operand.IsEquivalentTo(lastReturn.Operand))
{
if (previousIf.Condition.IsConstant)
{
// the condition is constant, and the returns return the same thing.
// get rid of the if statement altogether.
// transform: if(cond)return expr;return expr} to return expr}
DetachReferences.Apply(previousReturn.Operand);
node.RemoveAt(indexPrevious);
somethingChanged = true;
}
else
{
// transform: if(cond)return expr;return expr} to return cond,expr}
// create a new binary op with the condition and the final-return operand,
// replace the operand on the final-return with the new binary operator,
// and then delete the previous if-statement
DetachReferences.Apply(previousReturn.Operand);
lastReturn.Operand = CommaOperator.CombineWithComma(null, m_parser, previousIf.Condition, lastReturn.Operand);
node.RemoveAt(indexPrevious);
somethingChanged = true;
}
}
else
{
// transform: if(cond)return expr1;return expr2} to return cond?expr1:expr2}
// create a new conditional with the condition and the return operands,
// replace the operand on the final-return with the new conditional operator,
// and then delete the previous if-statement
// transform: if(cond)return expr1;return expr2} to return cond?expr1:expr2}
conditional = new Conditional(null, m_parser)
{
Condition = previousIf.Condition,
TrueExpression = previousReturn.Operand,
FalseExpression = lastReturn.Operand
};
// replace the operand on the final-return with the new conditional operator,
// and then delete the previous if-statement
lastReturn.Operand = conditional;
node.RemoveAt(indexPrevious);
Optimize(conditional);
somethingChanged = true;
}
}
}
if (!somethingChanged)
{
// nothing changed -- break out of the loop
break;
}
else
{
// set the flag that indicates something changed in at least one of these loops
changedStatementToExpression = true;
// and since we changed something, we need to bump the index down one
// AFTER we grab the last return node (which has slipped into the same position
// as the previous node)
lastReturn = node[indexPrevious--] as ReturnNode;
}
}
// if we added any more expressions since we ran our expression-combination logic,
// run it again.
if (changedStatementToExpression
&& m_parser.Settings.IsModificationAllowed(TreeModifications.CombineAdjacentExpressionStatements))
{
CombineExpressions(node);
}
// and FINALLY, we want to see if what we did previously didn't pan out and we end
// in something like return cond?expr:void 0, in which case we want to change it
// back to a simple if(condition)return expr; (saves four bytes).
// see if the last statement is a return statement that returns a conditional
if (lastReturn != null
&& (conditional = lastReturn.Operand as Conditional) != null)
{
var unaryOperator = conditional.FalseExpression as UnaryOperator;
if (unaryOperator != null
&& unaryOperator.OperatorToken == JSToken.Void
&& unaryOperator.Operand is ConstantWrapper)
{
unaryOperator = conditional.TrueExpression as UnaryOperator;
if (unaryOperator != null && unaryOperator.OperatorToken == JSToken.Void)
{
if (isFunctionLevel)
{
// transform: ...;return cond?void 0:void 0} to ...;cond}
// function level ends in an implicit "return void 0"
node.ReplaceChild(lastReturn, conditional.Condition);
}
else
{
// transform: ...;return cond?void 0:void 0} to ...;cond;return}
// non-function level doesn't end in an implicit return,
// so we need to break them out into two statements
node.ReplaceChild(lastReturn, conditional.Condition);
node.Append(new ReturnNode(null, m_parser));
}
}
else if (isFunctionLevel)
{
// transform: ...;return cond?expr:void 0} to ...;if(cond)return expr}
// (only works at the function-level because of the implicit return statement)
var ifNode = new IfNode(lastReturn.Context, m_parser)
{
Condition = conditional.Condition,
TrueBlock = AstNode.ForceToBlock(new ReturnNode(null, m_parser)
{
Operand = conditional.TrueExpression
})
};
node.ReplaceChild(lastReturn, ifNode);
}
}
else if (isFunctionLevel)
{
unaryOperator = conditional.TrueExpression as UnaryOperator;
if (unaryOperator != null
&& unaryOperator.OperatorToken == JSToken.Void
&& unaryOperator.Operand is ConstantWrapper)
{
// transform: ...;return cond?void 0;expr} to ...;if(!cond)return expr}
// (only works at the function level because of the implicit return)
// get the logical-not of the conditional
var logicalNot = new LogicalNot(conditional.Condition, m_parser);
logicalNot.Apply();
// create a new if-node based on the condition, with the branches swapped
// (true-expression goes to false-branch, false-expression goes to true-branch
var ifNode = new IfNode(lastReturn.Context, m_parser)
{
Condition = conditional.Condition,
TrueBlock = AstNode.ForceToBlock(new ReturnNode(null, m_parser)
{
Operand = conditional.FalseExpression
})
};
node.ReplaceChild(lastReturn, ifNode);
}
}
}
}
if (m_parser.Settings.IsModificationAllowed(TreeModifications.CombineEquivalentIfReturns))
{
// walk backwards looking for if(cond1)return expr1;if(cond2)return expr2;
// (backwards, because we'll be combining those into one statement, reducing the number of statements.
// don't go all the way to zero, because each loop will compare the statement to the PREVIOUS
// statement, and the first statement (index==0) has no previous statement.
for (var ndx = node.Count - 1; ndx > 0; --ndx)
{
// see if the current statement is an if-statement with no else block, and a true
// block that contains a single return-statement WITH an expression.
AstNode currentExpr = null;
AstNode condition2;
if (IsIfReturnExpr(node[ndx], out condition2, ref currentExpr) != null)
{
// see if the previous statement is also the same pattern, but with
// the equivalent expression as its return operand
AstNode condition1;
var matchedExpression = currentExpr;
var ifNode = IsIfReturnExpr(node[ndx - 1], out condition1, ref matchedExpression);
if (ifNode != null)
{
// it is a match!
// let's combine them -- we'll add the current condition to the
// previous condition with a logical-or and delete the current statement.
// transform: if(cond1)return expr;if(cond2)return expr; to if(cond1||cond2)return expr;
ifNode.Condition = new BinaryOperator(null, m_parser)
{
Operand1 = condition1,
Operand2 = condition2,
OperatorToken = JSToken.LogicalOr,
TerminatingContext = ifNode.TerminatingContext ?? node.TerminatingContext
};
DetachReferences.Apply(currentExpr);
node.RemoveAt(ndx);
}
}
}
}
if (isFunctionLevel
&& m_parser.Settings.IsModificationAllowed(TreeModifications.InvertIfReturn))
{
// walk backwards looking for if (cond) return; whenever we encounter that statement,
// we can change it to if (!cond) and put all subsequent statements in the block inside the
// if's true-block.
for (var ndx = node.Count - 1; ndx >= 0; --ndx)
{
var ifNode = node[ndx] as IfNode;
if (ifNode != null
&& ifNode.FalseBlock == null
&& ifNode.TrueBlock != null
&& ifNode.TrueBlock.Count == 1)
{
var returnNode = ifNode.TrueBlock[0] as ReturnNode;
if (returnNode != null && returnNode.Operand == null)
{
// we have if(cond)return;
// logical-not the condition, remove the return statement,
// and move all subsequent sibling statements inside the if-statement.
LogicalNot.Apply(ifNode.Condition, m_parser);
ifNode.TrueBlock.Clear();
var ndxMove = ndx + 1;
if (node.Count == ndxMove + 1)
{
// there's only one statement after our if-node.
// see if it's ALSO an if-node with no else block.
var secondIfNode = node[ndxMove] as IfNode;
if (secondIfNode != null && (secondIfNode.FalseBlock == null || secondIfNode.FalseBlock.Count == 0))
{
// it is!
// transform: if(cond1)return;if(cond2){...} => if(!cond1&&cond2){...}
// (the cond1 is already inverted at this point)
// combine cond2 with cond1 via a logical-and,
// move all secondIf statements inside the if-node,
// remove the secondIf node.
node.RemoveAt(ndxMove);
ifNode.Condition = new BinaryOperator(null, m_parser)
{
Operand1 = ifNode.Condition,
Operand2 = secondIfNode.Condition,
OperatorToken = JSToken.LogicalAnd
};
ifNode.TrueBlock = secondIfNode.TrueBlock;
}
else if (node[ndxMove].IsExpression
&& m_parser.Settings.IsModificationAllowed(TreeModifications.IfConditionCallToConditionAndCall))
{
// now we have if(cond)expr; optimize that!
var expression = node[ndxMove];
node.RemoveAt(ndxMove);
IfConditionExpressionToExpression(ifNode, expression);
}
}
// just move all the following statements inside the if-statement
while (node.Count > ndxMove)
{
var movedNode = node[ndxMove];
node.RemoveAt(ndxMove);
ifNode.TrueBlock.Append(movedNode);
}
}
}
}
}
else
{
var isIteratorBlock = node.Parent is ForNode
|| node.Parent is ForIn
|| node.Parent is WhileNode
|| node.Parent is DoWhile;
if (isIteratorBlock
&& m_parser.Settings.IsModificationAllowed(TreeModifications.InvertIfContinue))
{
// walk backwards looking for if (cond) continue; whenever we encounter that statement,
// we can change it to if (!cond) and put all subsequent statements in the block inside the
// if's true-block.
for (var ndx = node.Count - 1; ndx >= 0; --ndx)
{
var ifNode = node[ndx] as IfNode;
if (ifNode != null
&& ifNode.FalseBlock == null
&& ifNode.TrueBlock != null
&& ifNode.TrueBlock.Count == 1)
{
var continueNode = ifNode.TrueBlock[0] as ContinueNode;
// if there's no label, then we're good. Otherwise we can only make this optimization
// if the label refers to the parent iterator node.
if (continueNode != null
&& (string.IsNullOrEmpty(continueNode.Label) || (LabelMatchesParent(continueNode.Label, node.Parent))))
{
// if this is the last statement, then we don't really need the if at all
// and can just replace it with its condition
if (ndx < node.Count - 1)
{
// we have if(cond)continue;st1;...stn;
// logical-not the condition, remove the continue statement,
// and move all subsequent sibling statements inside the if-statement.
LogicalNot.Apply(ifNode.Condition, m_parser);
ifNode.TrueBlock.Clear();
// TODO: if we removed a labeled continue, do we need to fix up some label references?
var ndxMove = ndx + 1;
if (node.Count == ndxMove + 1)
{
// there's only one statement after our if-node.
// see if it's ALSO an if-node with no else block.
var secondIfNode = node[ndxMove] as IfNode;
if (secondIfNode != null && (secondIfNode.FalseBlock == null || secondIfNode.FalseBlock.Count == 0))
{
// it is!
// transform: if(cond1)continue;if(cond2){...} => if(!cond1&&cond2){...}
// (the cond1 is already inverted at this point)
// combine cond2 with cond1 via a logical-and,
// move all secondIf statements inside the if-node,
// remove the secondIf node.
ifNode.Condition = new BinaryOperator(null, m_parser)
{
Operand1 = ifNode.Condition,
Operand2 = secondIfNode.Condition,
OperatorToken = JSToken.LogicalAnd
};
ifNode.TrueBlock = secondIfNode.TrueBlock;
node.RemoveAt(ndxMove);
}
else if (node[ndxMove].IsExpression
&& m_parser.Settings.IsModificationAllowed(TreeModifications.IfConditionCallToConditionAndCall))
{
// now we have if(cond)expr; optimize that!
var expression = node[ndxMove];
node.RemoveAt(ndxMove);
IfConditionExpressionToExpression(ifNode, expression);
}
}
// just move all the following statements inside the if-statement
while (node.Count > ndxMove)
{
var movedNode = node[ndxMove];
node.RemoveAt(ndxMove);
ifNode.TrueBlock.Append(movedNode);
}
}
else
{
// we have if(cond)continue} -- nothing after the if.
// the loop is going to continue anyway, so replace the if-statement
// with the condition and be done
if (ifNode.Condition.IsConstant)
{
// consition is constant -- get rid of the if-statement altogether
node.RemoveAt(ndx);
}
else
{
// condition isn't constant
node[ndx] = ifNode.Condition;
}
}
}
}
}
}
}
}
}
public override void Visit(BinaryOperator node)
{
if (node != null)
{
base.Visit(node);
// see if this operation is subtracting zero from a lookup -- that is typically done to
// coerce a value to numeric. There's a simpler way: unary plus operator.
if (node.OperatorToken == JSToken.Minus
&& m_parser.Settings.IsModificationAllowed(TreeModifications.SimplifyStringToNumericConversion))
{
Lookup lookup = node.Operand1 as Lookup;
if (lookup != null)
{
ConstantWrapper right = node.Operand2 as ConstantWrapper;
if (right != null && right.IsIntegerLiteral && right.ToNumber() == 0)
{
// okay, so we have "lookup - 0"
// this is done frequently to force a value to be numeric.
// There is an easier way: apply the unary + operator to it.
// transform: lookup - 0 => +lookup
var unary = new UnaryOperator(node.Context, m_parser)
{
Operand = lookup,
OperatorToken = JSToken.Plus
};
node.Parent.ReplaceChild(node, unary);
// because we recursed at the top of this function, we don't need to Analyze
// the new Unary node. This visitor's method for UnaryOperator only does something
// if the operand is a constant -- and this one is a Lookup. And we already analyzed
// the lookup.
}
}
}
else if ((node.OperatorToken == JSToken.StrictEqual || node.OperatorToken == JSToken.StrictNotEqual)
&& m_parser.Settings.IsModificationAllowed(TreeModifications.ReduceStrictOperatorIfTypesAreSame))
{
PrimitiveType leftType = node.Operand1.FindPrimitiveType();
if (leftType != PrimitiveType.Other)
{
PrimitiveType rightType = node.Operand2.FindPrimitiveType();
if (leftType == rightType)
{
// the are the same known types. We can reduce the operators
node.OperatorToken = node.OperatorToken == JSToken.StrictEqual ? JSToken.Equal : JSToken.NotEqual;
}
else if (rightType != PrimitiveType.Other)
{
// they are not the same, but they are both known. We can completely remove the operator
// and replace it with true (!==) or false (===).
// transform: x !== y => true
// transform: x === y => false
node.Context.HandleError(JSError.StrictComparisonIsAlwaysTrueOrFalse, false);
node.Parent.ReplaceChild(
node,
new ConstantWrapper(node.OperatorToken == JSToken.StrictNotEqual, PrimitiveType.Boolean, node.Context, m_parser));
// because we are essentially removing the node from the AST, be sure to detach any references
DetachReferences.Apply(node);
}
}
}
else if (node.IsAssign)
{
var lookup = node.Operand1 as Lookup;
if (lookup != null)
{
if (lookup.VariableField != null && lookup.VariableField.InitializationOnly)
{
// the field is an initialization-only field -- we should NOT be assigning to it
lookup.Context.HandleError(JSError.AssignmentToConstant, true);
}
else if (m_scopeStack.Peek().UseStrict)
{
if (lookup.VariableField == null || lookup.VariableField.FieldType == FieldType.UndefinedGlobal)
{
// strict mode cannot assign to undefined fields
node.Operand1.Context.HandleError(JSError.StrictModeUndefinedVariable, true);
}
else if(lookup.VariableField.FieldType == FieldType.Arguments
|| (lookup.VariableField.FieldType == FieldType.Predefined && string.CompareOrdinal(lookup.Name, "eval") == 0))
{
// strict mode cannot assign to lookup "eval" or "arguments"
node.Operand1.Context.HandleError(JSError.StrictModeInvalidAssign, true);
}
}
}
}
else if ((node.Parent is Block || (node.Parent is CommaOperator && node.Parent.Parent is Block))
&& (node.OperatorToken == JSToken.LogicalOr || node.OperatorToken == JSToken.LogicalAnd))
{
// this is an expression statement where the operator is || or && -- basically
// it's a shortcut for an if-statement:
// expr1&&expr2; ==> if(expr1)expr2;
// expr1||expr2; ==> if(!expr1)expr2;
// let's check to see if the not of expr1 is smaller. If so, we can not the expression
// and change the operator
var logicalNot = new LogicalNot(node.Operand1, node.Parser);
if (logicalNot.Measure() < 0)
{
// it would be smaller! Change it.
// transform: expr1&&expr2 => !expr1||expr2
// transform: expr1||expr2 => !expr1&&expr2
logicalNot.Apply();
node.OperatorToken = node.OperatorToken == JSToken.LogicalAnd ? JSToken.LogicalOr : JSToken.LogicalAnd;
}
}
}
}
private void IfConditionExpressionToExpression(IfNode ifNode, AstNode expression)
{
// but first -- which operator to use? if(a)b --> a&&b, and if(!a)b --> a||b
// so determine which one is smaller: a or !a
// assume we'll use the logical-and, since that doesn't require changing the condition
var newOperator = JSToken.LogicalAnd;
var logicalNot = new LogicalNot(ifNode.Condition, m_parser);
if (logicalNot.Measure() < 0)
{
// !a is smaller, so apply it and use the logical-or operator
logicalNot.Apply();
newOperator = JSToken.LogicalOr;
}
// because the true block is an expression, we know it must only have
// ONE statement in it, so we can just dereference it directly.
var binaryOp = new BinaryOperator(ifNode.Context, m_parser)
{
Operand1 = ifNode.Condition,
Operand2 = expression,
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
ifNode.Parent.ReplaceChild(ifNode, binaryOp);
}
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;
}
}
}
}