net.sf.saxon.expr
public final class TypeChecker extends Object
Method Summary | |
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static XPathException | ebvError(Expression exp, TypeHierarchy th)
Test whether a given expression is capable of returning a value that has an effective boolean
value. |
static Expression | staticTypeCheck(Expression supplied, SequenceType req, boolean backwardsCompatible, RoleLocator role, ExpressionVisitor visitor)
Check an expression against a required type, modifying it if necessary.
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static Expression | strictTypeCheck(Expression supplied, SequenceType req, RoleLocator role, StaticContext env)
Check an expression against a required type, modifying it if necessary. |
static XPathException | testConformance(ValueRepresentation val, SequenceType requiredType, XPathContext context)
Test whether a given value conforms to a given type |
Parameters: exp the given expression th the type hierarchy cache
Returns: null if the expression is OK (optimistically), an exception object if not
This method takes the supplied expression and checks to see whether it is known statically to conform to the specified type. There are three possible outcomes. If the static type of the expression is a subtype of the required type, the method returns the expression unchanged. If the static type of the expression is incompatible with the required type (for example, if the supplied type is integer and the required type is string) the method throws an exception (this results in a compile-time type error being reported). If the static type is a supertype of the required type, then a new expression is constructed that evaluates the original expression and checks the dynamic type of the result; this new expression is returned as the result of the method.
The rules applied are those for function calling in XPath, that is, the rules that the argument of a function call must obey in relation to the signature of the function. Some contexts require slightly different rules (for example, operands of polymorphic operators such as "+"). In such cases this method cannot be used.
Note that this method does not do recursive type-checking of the sub-expressions.
Parameters: supplied The expression to be type-checked req The required type for the context in which the expression is used backwardsCompatible True if XPath 1.0 backwards compatibility mode is applicable role Information about the role of the subexpression within the containing expression, used to provide useful error messages visitor An expression visitor
Returns: The original expression if it is type-safe, or the expression wrapped in a run-time type checking expression if not.
Throws: XPathException if the supplied type is statically inconsistent with the required type (that is, if they have no common subtype)
Parameters: supplied The expression to be type-checked req The required type for the context in which the expression is used role Information about the role of the subexpression within the containing expression, used to provide useful error messages env The static context containing the types being checked. At present this is used only to locate a NamePool
Returns: The original expression if it is type-safe, or the expression wrapped in a run-time type checking expression if not.
Throws: XPathException if the supplied type is statically inconsistent with the required type (that is, if they have no common subtype)
Parameters: val the value requiredType the required type context XPath dynamic context
Returns: an XPathException describing the error condition if the value doesn't conform; or null if it does.
Throws: XPathException if a failure occurs reading the value