Contextual typing

摘要

Type inference is used to provide the benefits of static type checking without explicitly declaring type in the source code. Type inference that proceeds in a bottom up direction is augmented by contextual typing that proceeds in a top down direction. Contextual typing types enclosed expressions by associating the type of a directly enclosing expression with the enclosed expression. Object literals, function literals and array literals enclosed in assignment and call expressions, can be contextually typed.

主权项

1. A method comprising:
receiving a parse tree representing program source code by a processor of a software development computer, the program source code comprising at least one enclosing expression, the enclosing expression enclosing at least one enclosed expression; assigning a type associated with the enclosing expression to the at least one enclosed expression by:
evaluating the at least one enclosing expression of the parse tree for applicability of contextual typing by:
comparing the at least one enclosing expression of the parse tree with a set of templates;selecting a template from the set of templates, the selected template matching the at least one enclosing expression, the selected template associated with a process for assigning a type to the at least one enclosed expression; andassigning a type to the at least one enclosed expression by performing the process for assigning type to the at least one enclosed expression associated with the selected template in a top down direction; and providing type information for the at least one enclosed expression whose type is inferred from the type of an expression that encloses the enclosed expression on a display device.