RFR: addressing several issues in the implementation of universal tvars [v6]

[Vicente Romero]

On Tue, 7 Jun 2022 14:37:18 GMT, Maurizio Cimadamore <mcimadamore at openjdk.org> wrote:

>> Vicente Romero has updated the pull request incrementally with one additional commit since the last revision:
>> 
>>   adding structural type comparator to detect unchecked conversions
>
> src/jdk.compiler/share/classes/com/sun/tools/javac/code/Types.java line 1171:
> 
>> 1169:             @Override
>> 1170:             public Boolean visitType(Type t, Type s) {
>> 1171:                 switch (t.getTag()) {
> 
> In general - it seems like this routine has been brought in from isSubtype, which I think is wrong. This should borrow the most from isSameType. I believe in the case of this visitor, it would have been ok to simply return true if the two types have same tags? E.g. doesn't seem like adding the `switch` really adds much.

agreed

> src/jdk.compiler/share/classes/com/sun/tools/javac/code/Types.java line 1179:
> 
>> 1177:                     case BOT: case NONE:
>> 1178:                         return t.hasTag(s.getTag());
>> 1179:                     case WILDCARD: //we shouldn't be here - avoids crash (see 7034495)
> 
> comment seems copy and paste error?

I wasn't sure if this code for wildcards should be there or not, removing it

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PR: https://git.openjdk.java.net/valhalla/pull/684