Fix for rakudo/rakudo#2178 #2749
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The fix is done by implementing cooperation between dispatchers. If a dispatcher finds out that next call in the queue is a invocation handler with attribute $!dispatcher containing a object of descendant type of Metamodel::BaseDispatcher it passes control over to that dispatcher by calling either enter_with_args or enter_with_capture method. The subsequent dispatcher passes control back to the calling dispatcher upon exhausting its own queue. The known problems of this fix: - there is no clear way to determine if next call is a invocation handler. The approach used by this fix is to wrap the attempt to read from $!dispatcher attribute into a try block is hacky and would have performance penalty. Must be changed as soon as more straightforward approach is developed or found. - The enter_* methods are currently specific to the WrapDisptacher. So far there is seemingly no way to create a invocation handler with method or multi dispatcher in $!dispatcher and get such handler inserted into the WrapDispatcher queue. But neither there is no guaranty that no other such dispatcher would be developed in the future. For this reason the enter_* methods must be standartized and possibly moved into BaseDispatcher class.
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A problem has been discovered which needs fixing before this PR is ready. |
For wrapper-like dispatchers (with WrapDispatcher being currently the only one) we won't set explicit dispatcher for the last candidate on the queue effectively allowing a control call like callsame/nextsame to obtain routine's default dispatcher. This fixes a situation when a wrapped method cannot pass control over to the next method on MethodDispatcher queue. rakudo#2178
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The problem has been resolved, this PR is ready for review. |
MasterDuke17
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Mar 9, 2019
vrurg
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Mar 9, 2019
In support to PR rakudo/rakudo#2749
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The fix is done by implementing cooperation between dispatchers. If a
dispatcher finds out that next call in the queue is a invocation handler
with attribute
$!dispatchercontaining a object of descendant type ofMetamodel::BaseDispatcherit passes control over to that dispatcher bycalling either
enter_with_argsorenter_with_capturemethod. Thesubsequent dispatcher passes control back to the calling dispatcher upon
exhausting its own queue.
The known problems of this fix:
handler. The approach used by this fix is to wrap the attempt to read
from
$!dispatcherattribute into a try block is hacky and would haveperformance penalty. Must be changed as soon as more straightforward
approach is developed or found.
#2178