Bugzilla – Full Text Bug Listing
| Summary: | [1.5][wildcards] Not-necessarily-unbounded wildcards in method formal parameter types | ||
|---|---|---|---|
| Product: | [Eclipse Project] JDT | Reporter: | John Maraist <from-eclipse> |
| Component: | Core | Assignee: | Philipe Mulet <philippe_mulet> |
| Status: | VERIFIED FIXED | QA Contact: | |
| Severity: | normal | ||
| Priority: | P3 | CC: | BJGeraci |
| Version: | 3.1 | ||
| Target Milestone: | 3.1 M3 | ||
| Hardware: | PC | ||
| OS: | All | ||
| Whiteboard: | |||
JDT compiler still complains with last build I200410260800:
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1. ERROR in D:\usr\OTI\workspaces\dvpt\v31\HEAD\_Bug\BB.java (at line 2)
public boolean m(AA<U, ?> wht) { return wht.z().b(); }
^
Bound mismatch: The type ? is not a valid substitute for the bounded parameter
<Z extends AA<W,Z>> of the type AA<W,Z>
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1 problem (1 error)
Added regression test: GenericTypeTest#test378. Rewrote the type argument comparisons. Fixed Verified for 3.1 M3 with build I200411040800 |
System: - Eclipse 3.1M2 - Mandrake 10.0 This code exhibits inconsistant behavior on the Sun and Eclipse compilers. interface AA<W, Z extends AA<W, Z>> { public boolean m(AA<W, ?> that); public Z z(); public boolean b(); } abstract class BB<U, V extends AA<U, V>> implements AA<U,V> { public boolean m(AA<U, ?> wht) { return wht.z().b(); } } Note that - The formal type parameter Z of AA is bounded recursively by AA, - But the corresponding type argument of the declared type of formal parameter wht of method m's implementation is a wildcard with no bound. My understanding of unbounded wildcards is as an implicit bound of Object, which in this case means that in the body of m the expression "wht.z()" should be assumed to be Object, which does not have a method b(). The Eclipse compiler seems to reject this code for this reason:"'Bound mismatch: the type ? is not a valid substitute for the bounded parameter <Z extends AA<W,Z>> of type AA<W,Z>". On the other hand, any validly constructed actual parameter wht of type AA<U, ?> would certainly have been constructed respecting the bounds on Z. Perhaps this is why the Sun JDK javac accepts this code without error? I do not know which is the correct behavior, and am posting this bug to both the JDK and Eclipse bug pages. (Interface AA, by itself, compiles without error on both compilers.)