4517644: Core reflection setter type conversion spec bugs

[liach]

Current Status

In core reflection, there are a few holes with the documentation on the type conversions performed on the different setters. They generally follow this process:

1. The Object-valued setters checks the destination type. If that type is primitive, unbox the object.
2. Perform identity or (primitive/reference, depending on destination type) widening conversions.

For each step, they can fail with IllegalArgumentException, which has been the long standing behavior.

Note that this process is more restrictive than the JLS 5.2 assignment context, which allows boxing conversions, while the primitive reflective setters consistently reject them.

Problems

There are some problems with current specs:

1. No mention that boxing is never done for primitive-typed setters
2. Array.set missing description for the final identity or widening conversion (reference or primitive) and the associated IAE condition
3. Class specification of field mentions widening/narrowing conversion rules that is not sensible for get/set Object accessors
4. Field.set misses the identity or widening in IAE clause (but mentioned in main body)
5. Field primitive setters incorrectly claim they are equivalent to set(instance, wrapper) which is wrong due to lack of boxing conversion
6. Field primitive setters refer to nonsense "unwrapping conversion"

Solutions

1. Make sure the unbox -> identity/widen process and the IAE conditions are present in both Field and Array.set
2. Add that boxing is absent for all primitive setters
3. Update Field class spec to mention the narrowing/widening conversion limits are for primitive accessors only
4. Fix the Field primitive setters' "unwrapping conversion" to be "identity or primitive widening conversion" as in Array primitive setters
5. Qualify the Field primitive setters assertion with "if this field is of a primitive type" to make it correct

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Progress

• Change must be properly reviewed (1 review required, with at least 1 Reviewer)
• Change requires CSR request JDK-8370849 to be approved
• Change must not contain extraneous whitespace
• Commit message must refer to an issue

Issues

• JDK-4517644: Core reflection setter type conversion spec bugs (Bug - P4)
• JDK-8370849: Core reflection setter type conversion spec bugs (CSR)

Reviewing

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[bridgekeeper]

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[mlbridge]

Webrevs

• 01: Full - Incremental (5559e613)
• 00: Full (9f925617)

[AlanBateman]

The class description allows for widening but specifies IAE if a narrowing conversion is needed. Should we expand this sentence? I'm also wondering about identity conversions in description of each method as I don't know if this will be understand by readers without links.

[liach]

I think that paragraph most likely applies to the primitive accessors, because Object set are already performing necessary casts as narrowing conversions, and Object get never narrows its result. I should qualify this paragraph.

[liach]

I have pushed a commit correcting the class description paragraph in question to apply to primitive get/set only, and listed it in the problem and solutions sections on this PR and the CSR. Please review again.