[GitHub] [arrow] hermanschaaf opened a new issue, #34959: [Go] Support for casting to extension types

["hermanschaaf (via GitHub)" <gi...@apache.org>]

hermanschaaf opened a new issue, #34959:
URL: https://github.com/apache/arrow/issues/34959

   ### Describe the enhancement requested
   
   Right now it seems like there is support for casting from extension types to their underlying storage types, but not vice versa. 
   
   The `cast_test.go` tests include these cases, for example:
   
   ```
   canCast(types.NewSmallintType(), []arrow.DataType{arrow.PrimitiveTypes.Int16})
   canCast(types.NewSmallintType(), numericTypes)                                 // any cast which is valid for storage is supported
   canCast(arrow.Null, []arrow.DataType{types.NewSmallintType()})
   ```
   
   But adding this case, from the storage type to the extension type, fails:
   
   ```
   canCast(arrow.PrimitiveTypes.Int16, []arrow.DataType{types.NewSmallintType()}) // casting from storage type to extension is supported
   ```
   
   ```
   === RUN   TestCasts/TestCanCast
       cast_test.go:335: 
           	Error Trace:	/Users/hermanschaaf/code/cloudquery/arrow/go/arrow/compute/cast_test.go:335
           	            				/Users/hermanschaaf/code/cloudquery/arrow/go/arrow/compute/cast_test.go:341
           	            				/Users/hermanschaaf/code/cloudquery/arrow/go/arrow/compute/cast_test.go:401
           	Error:      	Not equal: 
           	            	expected: true
           	            	actual  : false
           	Test:       	TestCasts/TestCanCast
           	Messages:   	CanCast from: int16, to: extension_type<storage=int16>, expected: true
   ```
   
   It seems like this should be possible, as long as the type being cast from matches the storage type. Is there another way to do this that I might be missing? 
   
   ### Component(s)
   
   Go


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