Table of Contents

5.3.1.9 Implemented Name Declarations

This section corresponds to MS-VBAL §5.3.1.9 Implemented Name Declarations.

Static Semantics

A procedure of a class module is an implemented name declaration when its name is InterfaceName_MemberName: the name of an interface class the module implements (RD-VBAL §5.2.4.2), an underscore, and the name of a public variable or method of that class, the interface member. It is the same naming that handles an event (RD-VBAL §5.3.1.8) and a lifecycle event (RD-VBAL §5.3.1.10). VBClassModuleSymbol.FindImplementation finds it, of the kind the member calls for.

ImplementsSemantics reports an implemented name declaration that does not correspond to its member as VBC09330:

Interface member The implemented name declaration
A method The same kind of declaration: a subroutine, a function, a Property Get, a Property Let or a Property Set.
A variable A property declaration, and what it carries is of the variable's declared type: what a Get returns, the value parameter of a Let or a Set.
A method A parameter list equivalent to the member's: the same parameters, Optional parameters and ParamArray, each of the same declared type, constant default and parameter mechanism. The parameters may differ in name, and in whether the mechanism is written out.
A function, or a Property Get The same declared type.

A procedure that begins with an interface's prefix but is not named for one of its members is not an implemented name declaration, and is not checked. Only a default of a parameter that is a literal is compared.

Which of them a module needs is VBC09329: see RD-VBAL §5.2.4.2.

The Class interface that every class module implements is the one whose members need no implemented name declaration: each has an implementation of its own (SymbolProperties.DefaultImplementation), and VBClassModuleSymbol.IsImplemented says a member is implemented when there is a declaration or a default.

Runtime Semantics

When the target object of an invocation has a declared type that is an interface class of the actual class of the object, and the member named is a member of that interface class, the method invoked is the implemented name declaration of the object's class, not a member of the same name the class declares for itself. The same object is therefore dispatched by how the variable it is held in is declared:

Set d = New Disc    ' d As Disc
d.Draw              ' Disc's own Draw
Set s = d           ' s As IShape
s.Draw              ' Disc's IShape_Draw

A public variable of the interface is read through the Property Get that implements it.

The declared type of the expression the object is reached through is what the runtime asks, of the rules that type an expression at compile time (ExpressionStaticSemanticsEvaluator): a value carries the object and nothing of how it was declared. It is asked only of an object whose class implements an interface, and of an expression it can type. A with-relative member (.Area) is a member of the target of the innermost enclosing With block, so what is asked is the declared type of the expression the target was written as (RuntimeEvaluationContext.EnclosingWithTargetExpression): With s where s is declared as the interface dispatches .Area through it, and With d where d is declared as the class runs the class's own member.

Assigning to a public variable of the interface goes to the Property Let (or Property Set) that implements it, indexed or not, and so does an assignment in a With block.

⏮️ RD-VBAL §5.3.1.8 Event Handler Declarations | ⏭️ RD-VBAL §5.3.1.10 Lifecycle Handler Declarations

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