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[CLJ-1056] defprotocol: invalid method overload syntax getting accepted Created: 01/Sep/12  Updated: 25/Oct/13  Resolved: 25/Oct/13

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

Type: Defect Priority: Minor
Reporter: VĂ­ctor M. Valenzuela Assignee: Alex Miller
Resolution: Completed Votes: 0
Labels: errormsgs, protocols

Attachments: Text File clj-1056-1.txt     File clj-1056-2.diff     Text File clj-1056-2.txt    
Patch: Code and Test
Approval: Ok


The compiler accepts this erroneous form:

user=> (defprotocol Bar (m [this]) (m [this arg]))

Analysis: defprotocol silently assoc's the last list of signatures found for any particular method name, without checking whether the method name was given earlier.

Patch: clj-1056-2.diff

Approach: Modify defprotocol to check whether each method name has already been encountered earlier, and throw an exception if so. The patch also updates the error message for the case of a protocol function with no args specified.

Behavior with patch clj-1056-2.txt:

user=> (defprotocol Bar (m [this]) (m [this arg]))
IllegalArgumentException Function m in protocol Bar was redefined. Specify all arities in single definition.
user=> (defprotocol Foo (m []))
IllegalArgumentException Definition of function m in protocol Foo must take at least one arg.

Screened by: Stuart Halloway

Comment by Timothy Baldridge [ 29/Nov/12 4:02 PM ]

Can not reproduce the fist error:

user=> (defprotocol Foo (f ([this]) ([this arg])))
CompilerException java.lang.IllegalArgumentException: Parameter declaration missing, compiling:(NO_SOURCE_PATH:5:1)

But the 2nd one I can reproduce:

user=> (defprotocol Bar (m [this]) (m [this arg]))
user=> Bar
{:on-interface user.Bar, :on user.Bar, :sigs {:m {:doc nil, :arglists ([this arg]), :name m}}, :var #'user/Bar, :method-map {:m :m}, :method-builders {#'user/m #<user$eval71$fn_72 user$eval71$fn_72@1a2b53fb>}}

Notice that :arglists only has one entry


Comment by Alex Miller [ 22/Aug/13 10:36 PM ]

Moving back to Triaged as Rich has not vetted.

Comment by Andy Fingerhut [ 10/Sep/13 11:24 PM ]

Patch clj-1056-1.txt changes defprotocol to throw an exception if the same method name appears more than once.

Without this patch, the last set of signatures for a method name "wins", silently overriding any earlier ones.

Comment by Alex Miller [ 18/Oct/13 11:08 AM ]

Updated patch to improve error messages and to switch from CompilerException (which is not used outside the Compiler) back to IllegalArgumentException.

I think it would be a good idea to have a general Exception that could carry file/line/col info that could be used by Compiler but also other errors (the EdnReader and LispReader both have their own variants). But I think that should be a separate enhancement, which I have filed as CLJ-1280.

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