Type annotations for method/ctor reference expressions

Alex Buckley alex.buckley at oracle.com
Tue Dec 11 16:10:17 PST 2012

The following productions occur in the latest spec for JSR 335 "Lambda 
expressions" (v0.6 - I will send a URL to a suitably-licensed file 

  ExpressionName '::' NonWildTypeArgumentsopt Identifier
  Primary '::' NonWildTypeArgumentsopt Identifier
  'super' '::' NonWildTypeArgumentsopt Identifier
  TypeName '.' 'super' '::' NonWildTypeArgumentsopt Identifier
  ReferenceType '::' NonWildTypeArgumentsopt Identifier

  ClassType '::' NonWildTypeArgumentsopt 'new'
  ArrayType '::' 'new'

Some implications for JSR 308:

1. The NonWildTypeArguments term in MethodReference and 
ConstructorReference means that type arguments in method/ctor reference 
expressions are annotatable in source according to the current JSR 308 
grammar. (NonWildTypeArguments depends on ReferenceType, which the 308 
grammar makes annotatable.) For the class file, we have a target_type 
constant for method references, but there should be a separate constant 
for ctor references.

2. The ReferenceType term in MethodReference means that a type use there 
is annotatable in source. For the class file, a new target_type constant 
is needed.

3. The TypeName term in MethodReference should probably be annotatable 
in source. Come to think of it, what about annotating the TypeName in 
T.super.f (JLS 15.11.2)? Has JSR 308 missed this location all along?

4. The ClassType and ArrayType terms in ConstructorReference ought to be 
annotatable in source, but the JSR 308 grammar needs to be extended to 
allow this. Then new target_type constants are needed.


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