Common Type System—Coercion

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Common Type System Type Systems Intro § Types and Objects § Type Unification § Reference, Value Types § Accessibility, Visibility § Type Members § Fields § Methods § Locals Overloading Argument Passing Style Pass-by-Value and Pass-by-Reference Output Parameters Managed Pointers Variable Argument Methods Methods, Subclassing Virtuals, Overriding New Slots Exception Handlers Constructors, Instantiation § Default Constructors Value Construction Constructor Chaining Field Initialization Type Initializers Unhandled Exceptions Properties § Indexers Mixed Mode Accessibility Events Operator Overloading Coercion Subclassing, Polymorphism Styles of Inheritance § Implementation Inheritance Interface Inheritance Abstract Classes Interfaces § Method Dispatch Multiple Inheritance Private Interface Inheritance Private Inheritance Accessibility Interface Reimplementation Abstract and Interface? Sealing Types and Methods Runtime Type Checking Namespaces: Organizing Types § Define a Namespace Namespace Resolution Special Types § Delegates § CTS Support Co- and Contravariance Anonymous Delegates Custom Attributes Enumerations § Flags-Style Limitations Helper Methods Generics § Further Reading §

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Coercion

Coercion is the process of copying a scalar value from one type into an instance of another. This must occur when the target of an assignment is not of the same type of the right-hand, or assigned, value. For example, consider assigning a 32-bit float to a 64-bit double. We say coercion is widening if the target is of a larger storage capacity, as in the 32-bit to 64-bit conversion specified above, while it is narrowing if the target is of a lesser capacity. Widening coercions are implicitly supported by the runtime, while narrowing coercions can result in loss of information and are thus represented as explicit conversions.