Bugzilla – Full Text Bug Listing
| Summary: | [1.5][compiler] Generic type fallback | ||
|---|---|---|---|
| Product: | [Eclipse Project] JDT | Reporter: | Marvin Fröhlich <eclipse> |
| Component: | Core | Assignee: | Srikanth Sankaran <srikanth_sankaran> |
| Status: | VERIFIED INVALID | QA Contact: | |
| Severity: | normal | ||
| Priority: | P3 | CC: | Olivier_Thomann, satyam.kandula |
| Version: | 3.5 | ||
| Target Milestone: | 3.6 RC4 | ||
| Hardware: | PC | ||
| OS: | Linux | ||
| Whiteboard: | |||
(In reply to comment #0) > Build Identifier: 20090920-1017 > > Example class: > > ########### > class C<T extends Something> > { > public void m( T t ) {} > } > ########### > > If I enable "Usage of raw type" warnings, the following code will generate a > warning. > > ########### > C c = getACInstanceFromSomewhere(); > > c.m( new Something() ); > ########### > > If I "enrich" the code with question marks to eliminate the warning as follows, > the code will be uncompilable. > > ########### > C<?> c = getACInstanceFromSomewhere(); > > c.m( new Something() ); > ########### > > This is because Eclipse now assumes the following method signature for method > m. > > void v(? t) It is not upto the eclipse compiler to assume anything, it has to follow the java language specifications. The type safety rules related to generics require a conforming compiler to behave a certain way. See that in all the above scenarios eclipse behavior matches javac behavior with -Xlint:unchecked -Xlint:rawtypes options turned on. (The latter option may require a recent version of javac, probably of the javac7 pedigree. > This doesn't make any sense and looks like a bug to me. In the above case using > a question mark should make Eclipse assume the base type of the generic > argument ('Something'), but not ? or null. If no base type is given, Object > should be used. If you find any instance where eclipse behavior is at odds with javac behavior or at odds with the language specification, please raise a bug with suitable test cases. As it stands there is nothing for us to here. http://java.sun.com/j2se/1.5/pdf/generics-tutorial.pdf is a good resource that explains why many things are the way are. http://java.sun.com/docs/books/jls/download/langspec-3.0.pdf is the ultimate specification reference. (Some would argue that the entire generics thing is one big bug :), but that is neither here nor there) Verified for 3.6RC4 |
Build Identifier: 20090920-1017 Example class: ########### class C<T extends Something> { public void m( T t ) {} } ########### If I enable "Usage of raw type" warnings, the following code will generate a warning. ########### C c = getACInstanceFromSomewhere(); c.m( new Something() ); ########### If I "enrich" the code with question marks to eliminate the warning as follows, the code will be uncompilable. ########### C<?> c = getACInstanceFromSomewhere(); c.m( new Something() ); ########### This is because Eclipse now assumes the following method signature for method m. void v(? t) Sometimes Eclipse will even assume it like this. void v(null t) This doesn't make any sense and looks like a bug to me. In the above case using a question mark should make Eclipse assume the base type of the generic argument ('Something'), but not ? or null. If no base type is given, Object should be used. Reproducible: Always