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[CLJ-1363] Field access via .- in reflective case does not work Created: 18/Feb/14  Updated: 28/Feb/14  Resolved: 28/Feb/14

Status: Closed
Project: Clojure
Component/s: None
Affects Version/s: Release 1.5
Fix Version/s: Release 1.6

Type: Defect Priority: Major
Reporter: Alex Miller Assignee: Unassigned
Resolution: Completed Votes: 0
Labels: interop

Attachments: Text File clj-1363-v1.patch     Text File clj-1363-v2.patch     Text File clj-1363-v3.patch    
Patch: Code and Test
Approval: Ok

 Description   

The (.-foo instance) syntax will properly resolve to either a field or a no-arg method if the type of instance is known. However, in the reflective case, it will only resolve to a method. This behavior should match the non-reflective case. The method case always be forced by using (. foo (method)).

user> (definterface I (a []))
user.I
user> (deftype T [a] I (a [_] "method"))
user.T
user> (def t (->T "field"))
#'user/t
user=> (. ^T t a)  ;; as expected (prefer method)
"method"
user=> (. ^T t -a) ;; as expected (prefer field)
"field"
user> (. t a)      ;; as expected (prefer method)
"method"
user> (. t -a)     ;; WRONG - should return "field"
"method"

Approach: This case falls into Reflector.invokeNoArgInstanceMember() (this is the only place this method is used). InstanceFieldExpr now takes another flag (requireField) which will be set to true if "-field" and false if "field". InstanceFieldExpr will invoke (or emit) a call to Reflector.invokeNoArgInstanceMember() which now takes the same flag. If the flag is set to true, it first looks only for a field, otherwise it looks for a method and falls back to field which throws an error if necessary. I added a new invokeNoArgInstanceMember() with an arity to match the old arity - existing bytecode compiled on older Clojure versions will be trying to call this arity.

Patch: clj-1363-v3.patch

Screened by:



 Comments   
Comment by Rich Hickey [ 20/Feb/14 7:24 PM ]

You can't change the semantics of invokeNoArgInstanceMember - they are correct when not using '-'. We need to feed the info that '-' was used through InstanceFieldExpr and make field-first conditional on that.

Comment by Alex Miller [ 21/Feb/14 5:42 AM ]

Updated with new patch to thread this case through InstanceFieldExpr.

Comment by Andy Fingerhut [ 28/Feb/14 6:02 AM ]

A patch for this ticket has been committed as part of Clojure 1.6.0-beta2: https://github.com/clojure/clojure/commit/5fda6cb262d1807566ecadd3af9aaafb58ee5544

It appears this ticket could be closed now.

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