Class ExpressionOptimizer

Optimizer for expression trees.

Inheritance
System.Object
SafeExpressionVisitor
LvalExpressionVisitor
ExpressionOptimizer
Inherited Members
Namespace: System.Linq.Expressions
Assembly: Nuqleon.Linq.Expressions.Optimizers.dll
Syntax
public class ExpressionOptimizer : LvalExpressionVisitor

Constructors

ExpressionOptimizer(ISemanticProvider, IEvaluatorFactory)

Creates a new expression optimizer instance using the specified semantic semanticProvider and the specified evaluator evaluatorFactory.

Declaration
public ExpressionOptimizer(ISemanticProvider semanticProvider, IEvaluatorFactory evaluatorFactory)
Parameters
Type Name Description
ISemanticProvider semanticProvider

The semantic provider to use when performing various checks against expressions and reflection objects.
IEvaluatorFactory evaluatorFactory

The evaluator factory to use when evaluating a member or an expression at compile time.

Properties

EvaluatorFactory

Gets the evaluator factory to use when evaluating a member or an expression at compile time.

Declaration
public IEvaluatorFactory EvaluatorFactory { get; }
Property Value
Type Description
IEvaluatorFactory

SemanticProvider

Gets the semantic provider to use when performing various checks against expressions and reflection objects.

Declaration
public ISemanticProvider SemanticProvider { get; }
Property Value
Type Description
ISemanticProvider

Methods

ChangeType(Expression, Type)

Changes the static type of the specified expression to the specified type.

Declaration
protected Expression ChangeType(Expression expression, Type type)
Parameters
Type Name Description
System.Linq.Expressions.Expression expression

The expression whose static type to change.
System.Type type

The type to change the static type of the expression to.
Returns
Type Description
System.Linq.Expressions.Expression

The resulting expression with the specified static type.

Constant(Expression, Object, Type)

Creates an expression of type System.Linq.Expressions.ExpressionType.Constant with the specified value and type. The original expression is passed as well in order to allow overridden methods to suppress optimizations that produce an System.Linq.Expressions.ExpressionType.Constant node.

Declaration
protected virtual Expression Constant(Expression original, object value, Type type)
Parameters
Type Name Description
System.Linq.Expressions.Expression original

The original expression.
System.Object value

The value of the constant to create.
System.Type type

The static type of the node to return.
Returns
Type Description
System.Linq.Expressions.Expression

An expression representing the specified value of the specified type.

EvaluateIndex(IndexExpression)

Evaluates the indexer to perform constant folding.

Declaration
protected virtual Expression EvaluateIndex(IndexExpression node)
Parameters
Type Name Description
System.Linq.Expressions.IndexExpression node

The index expression to evaluate.
Returns
Type Description
System.Linq.Expressions.Expression

An expression containing the result of evaluating the specified index expression.

EvaluateInvocation(InvocationExpression)

Evaluates an invocation expression where the invocation target is a delegate.

Declaration
protected virtual Expression EvaluateInvocation(InvocationExpression node)
Parameters
Type Name Description
System.Linq.Expressions.InvocationExpression node

The invocation expression to evaluate.
Returns
Type Description
System.Linq.Expressions.Expression

An expression containing the result of evaluating the specified invocation expression.

EvaluateMember(MemberExpression)

Evaluates the member to perform constant folding.

Declaration
protected virtual Expression EvaluateMember(MemberExpression node)
Parameters
Type Name Description
System.Linq.Expressions.MemberExpression node

The member expression to evaluate.
Returns
Type Description
System.Linq.Expressions.Expression

An expression containing the result of evaluating the specified member expression.

EvaluateMethodCall(MethodCallExpression)

Evaluates the method call to perform constant folding.

Declaration
protected virtual Expression EvaluateMethodCall(MethodCallExpression node)
Parameters
Type Name Description
System.Linq.Expressions.MethodCallExpression node

The method call expression to evaluate.
Returns
Type Description
System.Linq.Expressions.Expression

An expression containing the result of evaluating the specified method call expression.

EvaluateNew(NewExpression)

Evaluates the constructor to perform constant folding.

Declaration
protected virtual Expression EvaluateNew(NewExpression node)
Parameters
Type Name Description
System.Linq.Expressions.NewExpression node

The new expression to evaluate.
Returns
Type Description
System.Linq.Expressions.Expression

An expression containing the result of evaluating the specified new expression.

GetEvaluator(Expression)

Gets an evaluator delegate for the specified expression that's free of parameters.

Declaration
protected virtual Func<object> GetEvaluator(Expression expression)
Parameters
Type Name Description
System.Linq.Expressions.Expression expression

The expression to get an evaluator delegate for.
Returns
Type Description
System.Func<System.Object>

A delegate that returns an System.Object with the result of evaluating the expression.

GetEvaluator(UnaryExpression)

Gets an evaluator delegate for the specified unary expression.

Declaration
protected virtual Func<object, object> GetEvaluator(UnaryExpression expression)
Parameters
Type Name Description
System.Linq.Expressions.UnaryExpression expression

The unary expression to get an evaluator delegate for.
Returns
Type Description
System.Func<System.Object, System.Object>

A delegate that takes an System.Object operand and returns an System.Object result.

GetEvaluator(MemberInfo)

Gets an evaluator delegate for the specified (pure) member.

Declaration
protected virtual Delegate GetEvaluator(MemberInfo member)
Parameters
Type Name Description
System.Reflection.MemberInfo member

The member to get an evaluator delegate for.
Returns
Type Description
System.Delegate

A delegate that takes zero or more System.Object parameters and returns either System.Object or System.Void.

GetRuntimeType(Expression)

Gets the runtime type of the result of evaluating the specified expression.

Declaration
protected Type GetRuntimeType(Expression expression)
Parameters
Type Name Description
System.Linq.Expressions.Expression expression

The expression whose runtime type to get.
Returns
Type Description
System.Type

The runtime type of the expression, if statically known; otherwise, null.
Remarks

This method checks if the specified expression does not throw in order to determine the runtime type. If an exception can occur during evaluation of the expression, a null reference is returned.

HasExactType(Expression)

Checks if the specified expression's static type matches the runtime type when evaluating the expression.

Declaration
protected virtual bool HasExactType(Expression expression)
Parameters
Type Name Description
System.Linq.Expressions.Expression expression

The expression to check.
Returns
Type Description
System.Boolean

true if the static type and the runtime type match; otherwise, false.
Remarks

This method can return true even if the specified expression may throw.

Null(Expression, Type)

Creates an expression representing a null value of the specified type. The original expression is passed as well in order to allow overridden methods to suppress optimizations that produce an System.Linq.Expressions.ExpressionType.Default node.

Declaration
protected virtual Expression Null(Expression original, Type type)
Parameters
Type Name Description
System.Linq.Expressions.Expression original

The original expression.
System.Type type

The type of the null value to return.
Returns
Type Description
System.Linq.Expressions.Expression

An expression representing null.

ShouldOptimize(Expression)

Checks if the specified expression should be optimized.

Declaration
protected virtual bool ShouldOptimize(Expression node)
Parameters
Type Name Description
System.Linq.Expressions.Expression node

The expression to check.
Returns
Type Description
System.Boolean

true if the expression should be optimized; otherwise, false.
Remarks

This method supports the suppression of optimizations to various nodes where optimization may be undesirable. An example is a node of type System.Linq.Expressions.ExpressionType.Quote.

Throw(Expression, Exception, Type)

Creates an expression of type System.Linq.Expressions.ExpressionType.Throw with the specified type used to throw the specified exception object obtained during evaluation of a pure member at compile time. The original expression is passed as well in order to allow overridden methods to suppress optimizations that produce an System.Linq.Expressions.ExpressionType.Throw node.

Declaration
protected virtual Expression Throw(Expression original, Exception exception, Type type)
Parameters
Type Name Description
System.Linq.Expressions.Expression original

The original expression.
System.Exception exception

The exception that was caught during evaluation of the expression.
System.Type type

The static type of the node to return.
Returns
Type Description
System.Linq.Expressions.Expression

An expression representing throwing the specified exception.

Throw(Expression, Expression, Type)

Creates an expression of type System.Linq.Expressions.ExpressionType.Throw with the specified type used to throw the specified exception expression. The original expression is passed as well in order to allow overridden methods to suppress optimizations that produce an System.Linq.Expressions.ExpressionType.Throw node.

Declaration
protected virtual Expression Throw(Expression original, Expression exception, Type type)
Parameters
Type Name Description
System.Linq.Expressions.Expression original

The original expression.
System.Linq.Expressions.Expression exception

The expression representing the exception to throw.
System.Type type

The static type of the node to return.
Returns
Type Description
System.Linq.Expressions.Expression

An expression representing throwing the specified exception expression.
Remarks

The introduction of System.Linq.Expressions.ExpressionType.Throw nodes may result in making the optimized expression tree bigger. However, if the exception gets propagated by the optimizer, it has the potential of pruning out a lot of nodes from the overall tree. Derived types can control the behavior by overriding this method as well as System.Linq.Expressions.ExpressionOptimizer.AlwaysThrows(System.Linq.Expressions.Expression).

TryChangeType(Expression, Type, out Expression)

Tries to change the static type of the specified expression to the specified type.

Declaration
protected virtual bool TryChangeType(Expression expression, Type type, out Expression result)
Parameters
Type Name Description
System.Linq.Expressions.Expression expression

The expression whose static type to change.
System.Type type

The type to change the static type of the expression to.
System.Linq.Expressions.Expression result

The resulting expression with the specified static type.
Returns
Type Description
System.Boolean

true if a change of type was possible; otherwise, false.

Visit(Expression)

Visits and expression tree and returns the optimized result.

Declaration
public override Expression Visit(Expression node)
Parameters
Type Name Description
System.Linq.Expressions.Expression node

The expression tree to visit.
Returns
Type Description
System.Linq.Expressions.Expression

An optimized rewritten expression, or the original expression if nothing was optimized.

VisitArgument(Expression, ParameterInfo)

Visits the expression argument using the corresponding parameter to determine whether the argument is assigned to a ref or out parameter. An argument that is passed by reference gets visited using VisitLval(Expression).

Declaration
protected override Expression VisitArgument(Expression argument, ParameterInfo parameter)
Parameters
Type Name Description
System.Linq.Expressions.Expression argument

The argument expression to visit.
System.Reflection.ParameterInfo parameter

The parameter corresponding to the argument.
Returns
Type Description
System.Linq.Expressions.Expression

The result of visiting the expression arguments.
Overrides

VisitBinaryWithConversion(BinaryExpression, Boolean)

Visits a binary expression with a System.Linq.Expressions.BinaryExpression.Conversion specified to perform optimization steps.

Declaration
protected override Expression VisitBinaryWithConversion(BinaryExpression node, bool isAssignment)
Parameters
Type Name Description
System.Linq.Expressions.BinaryExpression node

The binary expression to visit.
System.Boolean isAssignment

Indicates whether the node represents an assignment.
Returns
Type Description
System.Linq.Expressions.Expression

The result of optimizing the binary expression.
Overrides

VisitBinaryWithoutConversion(BinaryExpression, Boolean)

Visits a binary expression with no System.Linq.Expressions.BinaryExpression.Conversion specified to perform optimization steps.

Declaration
protected override Expression VisitBinaryWithoutConversion(BinaryExpression node, bool isAssignment)
Parameters
Type Name Description
System.Linq.Expressions.BinaryExpression node

The binary expression to visit.
System.Boolean isAssignment

Indicates whether the node represents an assignment.
Returns
Type Description
System.Linq.Expressions.Expression

The result of optimizing the binary expression.
Overrides

VisitBlock(BlockExpression)

Visits a block expression to perform optimization steps.

Declaration
protected override Expression VisitBlock(BlockExpression node)
Parameters
Type Name Description
System.Linq.Expressions.BlockExpression node

The block expression to visit.
Returns
Type Description
System.Linq.Expressions.Expression

The result of optimizing the block expression.

VisitCatchBlock(CatchBlock)

Visits a catch block to perform optimization steps.

Declaration
protected override CatchBlock VisitCatchBlock(CatchBlock node)
Parameters
Type Name Description
System.Linq.Expressions.CatchBlock node

The catch block to visit.
Returns
Type Description
System.Linq.Expressions.CatchBlock

The result of optimizing the catch block.

VisitConditional(ConditionalExpression)

Visits a conditional expression to perform optimization steps.

Declaration
protected override Expression VisitConditional(ConditionalExpression node)
Parameters
Type Name Description
System.Linq.Expressions.ConditionalExpression node

The conditional expression to visit.
Returns
Type Description
System.Linq.Expressions.Expression

The result of optimizing the conditional expression.

VisitIndex(IndexExpression, Boolean)

Visits an index expression to perform optimization steps.

Declaration
protected override Expression VisitIndex(IndexExpression node, bool isLval)
Parameters
Type Name Description
System.Linq.Expressions.IndexExpression node

The index expression to visit.
System.Boolean isLval

Indicates whether the node occurs in an lval position.
Returns
Type Description
System.Linq.Expressions.Expression

The result of optimizing the index expression.
Overrides

VisitInvocationCore(InvocationExpression)

Visits an invocation to perform optimization steps.

Declaration
protected override Expression VisitInvocationCore(InvocationExpression node)
Parameters
Type Name Description
System.Linq.Expressions.InvocationExpression node

The invocation to visit.
Returns
Type Description
System.Linq.Expressions.Expression

The result of optimizing the invocation.
Overrides

VisitLambdaInvocation(InvocationExpression)

Visits and invocation of a lambda expression to perform optimization steps.

Declaration
protected virtual Expression VisitLambdaInvocation(InvocationExpression node)
Parameters
Type Name Description
System.Linq.Expressions.InvocationExpression node

The invocation to visit.
Returns
Type Description
System.Linq.Expressions.Expression

The result of optimizing the invocation.

VisitMember(MemberExpression, Boolean)

Visits a member expression to perform optimization steps.

Declaration
protected override Expression VisitMember(MemberExpression node, bool isLval)
Parameters
Type Name Description
System.Linq.Expressions.MemberExpression node

The member expression to visit.
System.Boolean isLval

Indicates whether the node occurs in an lval position.
Returns
Type Description
System.Linq.Expressions.Expression

The result of optimizing the member expression.
Overrides

VisitMethodCallCore(MethodCallExpression)

Visits a method call expression to perform optimization steps.

Declaration
protected override Expression VisitMethodCallCore(MethodCallExpression node)
Parameters
Type Name Description
System.Linq.Expressions.MethodCallExpression node

The method call expression to visit.
Returns
Type Description
System.Linq.Expressions.Expression

The result of optimizing the method call expression.
Overrides

VisitNewArray(NewArrayExpression)

Visits a new array expression to perform optimization steps.

Declaration
protected override Expression VisitNewArray(NewArrayExpression node)
Parameters
Type Name Description
System.Linq.Expressions.NewArrayExpression node

The new array expression to visit.
Returns
Type Description
System.Linq.Expressions.Expression

The result of optimizing the new array expression.

VisitNewCore(NewExpression)

Visits a new expression to perform optimization steps.

Declaration
protected override Expression VisitNewCore(NewExpression node)
Parameters
Type Name Description
System.Linq.Expressions.NewExpression node

The new expression to visit.
Returns
Type Description
System.Linq.Expressions.Expression

The result of optimizing the new expression.
Overrides

VisitPostOptimize(Expression, Expression)

Visits an expression after optimizations have been applied.

Declaration
protected virtual Expression VisitPostOptimize(Expression original, Expression optimized)
Parameters
Type Name Description
System.Linq.Expressions.Expression original

The original expression returned from VisitPreOptimize(Expression).
System.Linq.Expressions.Expression optimized

The result of applying optimizations to the original expression.
Returns
Type Description
System.Linq.Expressions.Expression

The expression to return from the visitor.
Remarks

This method supports plugging in post-optimization rewrites or logging steps. It can also be used to undo an optimization.

VisitPreOptimize(Expression)

Visits the specified expression prior to applying optimizations.

Declaration
protected virtual Expression VisitPreOptimize(Expression node)
Parameters
Type Name Description
System.Linq.Expressions.Expression node

The expression to visit prior to applying optimizations.
Returns
Type Description
System.Linq.Expressions.Expression

The result of visiting the specified expression prior to optimization.
Remarks

This method supports plugging in pre-optimization rewrites or logging steps.

VisitSwitch(SwitchExpression)

Visits a switch expression to perform optimization steps.

Declaration
protected override Expression VisitSwitch(SwitchExpression node)
Parameters
Type Name Description
System.Linq.Expressions.SwitchExpression node

The switch expression to visit.
Returns
Type Description
System.Linq.Expressions.Expression

The result of optimizing the switch expression.

VisitTry(TryExpression)

Visits a try expression to perform optimization steps.

Declaration
protected override Expression VisitTry(TryExpression node)
Parameters
Type Name Description
System.Linq.Expressions.TryExpression node

The try expression to visit.
Returns
Type Description
System.Linq.Expressions.Expression

The result of optimizing the try expression.

VisitTypeBinary(TypeBinaryExpression)

Visits a type binary expression to perform optimization steps.

Declaration
protected override Expression VisitTypeBinary(TypeBinaryExpression node)
Parameters
Type Name Description
System.Linq.Expressions.TypeBinaryExpression node

The type binary expression to visit.
Returns
Type Description
System.Linq.Expressions.Expression

The result of optimizing the type binary expression.

VisitUnaryNonQuote(UnaryExpression, Boolean)

Visits a unary expression to perform optimization steps.

Declaration
protected override Expression VisitUnaryNonQuote(UnaryExpression node, bool isAssignment)
Parameters
Type Name Description
System.Linq.Expressions.UnaryExpression node

The unary expression to visit.
System.Boolean isAssignment

Indicates whether the node represents an assignment.
Returns
Type Description
System.Linq.Expressions.Expression

The result of optimizing the unary expression.
Overrides