// unnest any child blocks
private void UnnestBlocks(Block node)
{
// walk the list of items backwards -- if we come
// to any blocks, unnest the block recursively.
// Remove any empty statements as well.
// We walk backwards because we could be adding any number of statements
// and we don't want to have to modify the counter.
for (int ndx = node.Count - 1; ndx >= 0; --ndx)
{
var nestedBlock = node[ndx] as Block;
if (nestedBlock != null)
{
// unnest recursively
UnnestBlocks(nestedBlock);
// if the block has a block scope, then we can't really unnest it
// without merging lexical scopes
if (nestedBlock.BlockScope == null)
{
// remove the nested block
node.RemoveAt(ndx);
// then start adding the statements in the nested block to our own.
// go backwards so we can just keep using the same index
node.InsertRange(ndx, nestedBlock.Children);
}
}
else if (node[ndx] is EmptyStatement)
{
// remove empty statements (lone semicolons)
node.RemoveAt(ndx);
}
else if (ndx > 0)
{
// see if the previous node is a conditional-compilation comment, because
// we will also combine adjacent those
var previousComment = node[ndx - 1] as ConditionalCompilationComment;
if (previousComment != null)
{
ConditionalCompilationComment thisComment = node[ndx] as ConditionalCompilationComment;
if (thisComment != null)
{
// two adjacent conditional comments -- combine them into the first.
previousComment.Statements.Append(thisComment.Statements);
// and remove the second one (which is now a duplicate)
node.RemoveAt(ndx);
}
}
}
}
}
public override void Visit(Block node)
{
if (node != null)
{
// javascript doesn't have block scope, so there really is no point
// in nesting blocks. Unnest any now, before we start combining var statements
UnnestBlocks(node);
if (m_combineAdjacentVars)
{
// look at the statements in the block.
// if there are multiple var statements adjacent to each other, combine them.
// walk BACKWARDS down the list because we'll be removing items when we encounter
// multiple vars, etc.
// 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)
{
// if the previous node is not a Var, then we don't need to try and combine
// it with the current node
var previousVar = node[ndx - 1] as Var;
if (previousVar != null && node[ndx] is Var)
{
// add the items in this VAR to the end of the previous
previousVar.Append(node[ndx]);
// delete this item from the block
node.RemoveAt(ndx);
}
else
{
// do the same thing for lexical declarations
var previousLex = node[ndx - 1] as LexicalDeclaration;
var thisLex = node[ndx] as LexicalDeclaration;
if (previousLex != null && thisLex != null)
{
// but we can only combine them if they are the same type (let or const)
if (previousLex.StatementToken == thisLex.StatementToken)
{
previousLex.Append(node[ndx]);
node.RemoveAt(ndx);
}
}
else
{
// try doing the same for const-statements: combine adjacent ones
var previousConst = node[ndx - 1] as ConstStatement;
if (previousConst != null && node[ndx] is ConstStatement)
{
// they are both ConstStatements, so adding the current one to the
// previous one will combine them, then delete the latter one.
previousConst.Append(node[ndx]);
node.RemoveAt(ndx);
}
}
}
}
}
// recurse down the tree after we've combined the adjacent var statements
base.Visit(node);
}
}
// unnest any child blocks
private void UnnestBlocks(Block node)
{
// walk the list of items backwards -- if we come
// to any blocks, unnest the block recursively.
// Remove any empty statements as well.
// We walk backwards because we could be adding any number of statements
// and we don't want to have to modify the counter.
for (int ndx = node.Count - 1; ndx >= 0; --ndx)
{
var nestedBlock = node[ndx] as Block;
if (nestedBlock != null)
{
// unnest recursively
UnnestBlocks(nestedBlock);
// if the block has a block scope, then we can't really unnest it
// without merging lexical scopes
if (nestedBlock.BlockScope == null)
{
// remove the nested block
node.RemoveAt(ndx);
// then start adding the statements in the nested block to our own.
// go backwards so we can just keep using the same index
node.InsertRange(ndx, nestedBlock.Children);
}
}
else if (node[ndx] is EmptyStatement)
{
// remove empty statements (lone semicolons)
node.RemoveAt(ndx);
}
else if (ndx > 0)
{
// see if the previous node is a conditional-compilation comment, because
// we will also combine adjacent those
var previousComment = node[ndx - 1] as ConditionalCompilationComment;
if (previousComment != null)
{
ConditionalCompilationComment thisComment = node[ndx] as ConditionalCompilationComment;
if (thisComment != null)
{
// two adjacent conditional comments -- combine them into the first.
previousComment.Statements.Append(thisComment.Statements);
// and remove the second one (which is now a duplicate)
node.RemoveAt(ndx);
}
}
}
}
}
private static int RelocateVar(Block block, int insertAt, Var varStatement)
{
// if the var statement is at the next position to insert, then we don't need
// to do anything.
if (block[insertAt] != varStatement)
{
// check to see if the current position is a var and we are the NEXT statement.
// if that's the case, we don't need to break out the initializer, just append all the
// vardecls as-is to the current position.
var existingVar = block[insertAt] as Var;
if (existingVar != null && block[insertAt + 1] == varStatement)
{
// just append our vardecls to the insertion point, then delete our statement
existingVar.Append(varStatement);
block.RemoveAt(insertAt + 1);
}
else
{
// iterate through the decls and count how many have initializers
var initializerCount = 0;
for (var ndx = 0; ndx < varStatement.Count; ++ndx)
{
if (varStatement[ndx].Initializer != null)
{
++initializerCount;
}
}
// if there are more than two decls with initializers, then we won't actually
// be gaining anything by moving the var to the top. We'll get rid of the four
// bytes for the "var ", but we'll be adding two bytes for the name and comma
// because name=init will still need to remain behind.
if (initializerCount <= 2)
{
// first iterate through all the declarations in the var statement,
// constructing an expression statement that is made up of assignment
// operators for each of the declarations that have initializers (if any)
// and removing all the initializers
var assignments = new List<AstNode>();
for (var ndx = 0; ndx < varStatement.Count; ++ndx)
{
var varDecl = varStatement[ndx];
if (varDecl.Initializer != null)
{
if (varDecl.IsCCSpecialCase)
{
// create a vardecl with the same name and no initializer
var copyDecl = new VariableDeclaration(varDecl.Context, varDecl.Parser)
{
Identifier = varDecl.Identifier,
NameContext = varDecl.VariableField.OriginalContext,
VariableField = varDecl.VariableField
};
// replace the special vardecl with the copy
varStatement[ndx] = copyDecl;
// add the original vardecl to the list of "assignments"
assignments.Add(varDecl);
// add the new decl to the field's declaration list, and remove the old one
// because we're going to change that to an assignment.
varDecl.VariableField.Declarations.Add(copyDecl);
varDecl.VariableField.Declarations.Remove(varDecl);
}
else
{
// hold on to the object so we don't lose it to the GC
var initializer = varDecl.Initializer;
// remove it from the vardecl
varDecl.Initializer = null;
// create an assignment operator for a lookup to the name
// as the left, and the initializer as the right, and add it to the list
var lookup = new Lookup(varDecl.VariableField.OriginalContext, varDecl.Parser)
{
Name = varDecl.Identifier,
VariableField = varDecl.VariableField,
};
assignments.Add(new BinaryOperator(varDecl.Context, varDecl.Parser)
{
Operand1 = lookup,
Operand2 = initializer,
OperatorToken = JSToken.Assign,
OperatorContext = varDecl.AssignContext
});
// add the new lookup to the field's references
varDecl.VariableField.References.Add(lookup);
}
}
}
// now if there were any initializers...
if (assignments.Count > 0)
{
// we want to create one big expression from all the assignments and replace the
// var statement with the assignment(s) expression. Start at position n=1 and create
// a binary operator of n-1 as the left, n as the right, and using a comma operator.
var expression = assignments[0];
for (var ndx = 1; ndx < assignments.Count; ++ndx)
{
expression = CommaOperator.CombineWithComma(null, expression.Parser, expression, assignments[ndx]);
}
// replace the var with the expression.
// we still have a pointer to the var, so we can insert it back into the proper
// place next.
varStatement.Parent.ReplaceChild(varStatement, expression);
}
else
{
// no initializers.
// if the parent is a for-in statement...
var forInParent = varStatement.Parent as ForIn;
if (forInParent != null)
{
// we want to replace the var statement with a lookup for the var
// there should be only one vardecl
var varDecl = varStatement[0];
var lookup = new Lookup(varDecl.VariableField.OriginalContext, varStatement.Parser)
{
Name = varDecl.Identifier,
VariableField = varDecl.VariableField
};
varStatement.Parent.ReplaceChild(varStatement, lookup);
varDecl.VariableField.References.Add(lookup);
}
else
{
// just remove the var statement altogether
varStatement.Parent.ReplaceChild(varStatement, null);
}
}
// if the statement at the insertion point is a var-statement already,
// then we just need to append our vardecls to it. Otherwise we'll insert our
// var statement at the right point
if (existingVar != null)
{
// append the varstatement we want to move to the existing var, which will
// transfer all the vardecls to it.
existingVar.Append(varStatement);
}
else
{
// move the var to the insert point, incrementing the position or next time
block.Insert(insertAt, varStatement);
}
}
}
}
return insertAt;
}
public override void Visit(Block node)
{
if (node != null)
{
// javascript doesn't have block scope, so there really is no point
// in nesting blocks. Unnest any now, before we start combining var statements
UnnestBlocks(node);
if (m_combineAdjacentVars)
{
// look at the statements in the block.
// if there are multiple var statements adjacent to each other, combine them.
// walk BACKWARDS down the list because we'll be removing items when we encounter
// multiple vars, etc.
// 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)
{
// if the previous node is not a Var, then we don't need to try and combine
// it with the current node
var previousVar = node[ndx - 1] as Var;
if (previousVar != null && node[ndx] is Var)
{
// add the items in this VAR to the end of the previous
previousVar.Append(node[ndx]);
// delete this item from the block
node.RemoveAt(ndx);
}
else
{
// do the same thing for lexical declarations
var previousLex = node[ndx - 1] as LexicalDeclaration;
var thisLex = node[ndx] as LexicalDeclaration;
if (previousLex != null && thisLex != null)
{
// but we can only combine them if they are the same type (let or const)
if (previousLex.StatementToken == thisLex.StatementToken)
{
previousLex.Append(node[ndx]);
node.RemoveAt(ndx);
}
}
else
{
// try doing the same for const-statements: combine adjacent ones
var previousConst = node[ndx - 1] as ConstStatement;
if (previousConst != null && node[ndx] is ConstStatement)
{
// they are both ConstStatements, so adding the current one to the
// previous one will combine them, then delete the latter one.
previousConst.Append(node[ndx]);
node.RemoveAt(ndx);
}
}
}
}
}
// recurse down the tree after we've combined the adjacent var statements
base.Visit(node);
}
}
private static int RelocateVar(Block block, int insertAt, Var varStatement)
{
// if the var statement is at the next position to insert, then we don't need
// to do anything.
if (block[insertAt] != varStatement)
{
// check to see if the current position is a var and we are the NEXT statement.
// if that's the case, we don't need to break out the initializer, just append all the
// vardecls as-is to the current position.
var existingVar = block[insertAt] as Var;
if (existingVar != null && block[insertAt + 1] == varStatement)
{
// just append our vardecls to the insertion point, then delete our statement
existingVar.Append(varStatement);
block.RemoveAt(insertAt + 1);
}
else
{
// iterate through the decls and count how many have initializers
var initializerCount = 0;
for (var ndx = 0; ndx < varStatement.Count; ++ndx)
{
if (varStatement[ndx].Initializer != null)
{
++initializerCount;
}
}
// if there are more than two decls with initializers, then we won't actually
// be gaining anything by moving the var to the top. We'll get rid of the four
// bytes for the "var ", but we'll be adding two bytes for the name and comma
// because name=init will still need to remain behind.
if (initializerCount <= 2)
{
// first iterate through all the declarations in the var statement,
// constructing an expression statement that is made up of assignment
// operators for each of the declarations that have initializers (if any)
// and removing all the initializers
var assignments = new List <AstNode>();
for (var ndx = 0; ndx < varStatement.Count; ++ndx)
{
var varDecl = varStatement[ndx];
if (varDecl.Initializer != null)
{
if (varDecl.IsCCSpecialCase)
{
// create a vardecl with the same name and no initializer
var copyDecl = new VariableDeclaration(varDecl.Context, varDecl.Parser)
{
Identifier = varDecl.Identifier,
NameContext = varDecl.VariableField.OriginalContext,
VariableField = varDecl.VariableField
};
// replace the special vardecl with the copy
varStatement[ndx] = copyDecl;
// add the original vardecl to the list of "assignments"
assignments.Add(varDecl);
// add the new decl to the field's declaration list, and remove the old one
// because we're going to change that to an assignment.
varDecl.VariableField.Declarations.Add(copyDecl);
varDecl.VariableField.Declarations.Remove(varDecl);
}
else
{
// hold on to the object so we don't lose it to the GC
var initializer = varDecl.Initializer;
// remove it from the vardecl
varDecl.Initializer = null;
// create an assignment operator for a lookup to the name
// as the left, and the initializer as the right, and add it to the list
var lookup = new Lookup(varDecl.VariableField.OriginalContext, varDecl.Parser)
{
Name = varDecl.Identifier,
VariableField = varDecl.VariableField,
};
assignments.Add(new BinaryOperator(varDecl.Context, varDecl.Parser)
{
Operand1 = lookup,
Operand2 = initializer,
OperatorToken = JSToken.Assign,
OperatorContext = varDecl.AssignContext
});
// add the new lookup to the field's references
varDecl.VariableField.References.Add(lookup);
}
}
}
// now if there were any initializers...
if (assignments.Count > 0)
{
// we want to create one big expression from all the assignments and replace the
// var statement with the assignment(s) expression. Start at position n=1 and create
// a binary operator of n-1 as the left, n as the right, and using a comma operator.
var expression = assignments[0];
for (var ndx = 1; ndx < assignments.Count; ++ndx)
{
expression = CommaOperator.CombineWithComma(null, expression.Parser, expression, assignments[ndx]);
}
// replace the var with the expression.
// we still have a pointer to the var, so we can insert it back into the proper
// place next.
varStatement.Parent.ReplaceChild(varStatement, expression);
}
else
{
// no initializers.
// if the parent is a for-in statement...
var forInParent = varStatement.Parent as ForIn;
if (forInParent != null)
{
// we want to replace the var statement with a lookup for the var
// there should be only one vardecl
var varDecl = varStatement[0];
var lookup = new Lookup(varDecl.VariableField.OriginalContext, varStatement.Parser)
{
Name = varDecl.Identifier,
VariableField = varDecl.VariableField
};
varStatement.Parent.ReplaceChild(varStatement, lookup);
varDecl.VariableField.References.Add(lookup);
}
else
{
// just remove the var statement altogether
varStatement.Parent.ReplaceChild(varStatement, null);
}
}
// if the statement at the insertion point is a var-statement already,
// then we just need to append our vardecls to it. Otherwise we'll insert our
// var statement at the right point
if (existingVar != null)
{
// append the varstatement we want to move to the existing var, which will
// transfer all the vardecls to it.
existingVar.Append(varStatement);
}
else
{
// move the var to the insert point, incrementing the position or next time
block.Insert(insertAt, varStatement);
}
}
}
}
return(insertAt);
}
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;
}
}
}
}
}
}
}
}
}
private static void StripDebugStatements(Block node)
{
// walk the list backwards
for (int ndx = node.Count - 1; ndx >= 0; --ndx)
{
// if this item pops positive...
if (node[ndx].IsDebuggerStatement)
{
// just remove it
DetachReferences.Apply(node[ndx]);
node.RemoveAt(ndx);
}
}
}
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;
}
}
}
private void CombineWithPreviousExpression(Block node, int ndx)
{
IfNode ifNode;
ForNode forNode;
WhileNode whileNode;
ReturnNode returnNode;
if (node[ndx].IsExpression)
{
CombineTwoExpressions(node, ndx);
}
else if ((returnNode = node[ndx] as ReturnNode) != null)
{
CombineReturnWithExpression(node, ndx, returnNode);
}
else if ((forNode = node[ndx] as ForNode) != null)
{
CombineForNodeWithExpression(node, ndx, forNode);
}
else if ((ifNode = node[ndx] as IfNode) != null)
{
// transform: expr;if(cond)... => if(expr,cond)...
// combine the previous expression with the if-condition via comma, then delete
// the previous statement.
ifNode.Condition = CommaOperator.CombineWithComma(null, m_parser, node[ndx - 1], ifNode.Condition);
node.RemoveAt(ndx - 1);
}
else if ((whileNode = node[ndx] as WhileNode) != null
&& m_parser.Settings.IsModificationAllowed(TreeModifications.ChangeWhileToFor))
{
// transform: expr;while(cond)... => for(expr;cond;)...
// zero-sum, and maybe a little worse for performance because of the nop iterator,
// but combines two statements into one, which may have savings later on.
var initializer = node[ndx - 1];
node[ndx] = new ForNode(null, m_parser)
{
Initializer = initializer,
Condition = whileNode.Condition,
Body = whileNode.Body
};
node.RemoveAt(ndx - 1);
}
}
