Possible enhanced for loop failure

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#72 opened on Jun 14, 2020 0 comments 0 reactions 0 assignees View on GitHub

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Assessment

Difficulty: 4/5
Estimated time: 3-5 days
Newbie friendliness: 25/100

Issue type: Bug
Clarity: Needs clarification
Activity status: Stale
Tech stack: java
Domain: compilers

Research direction

Start with BackupList.func_230753_a_ and the enhanced-for-loop generation path that produces the shown iterator code. Compare the generated output with the source form and check the other similar cases mentioned in the issue. Done means the loop preserves the expected iterator assignment and existing behavior remains covered by the relevant decompiler tests.

Written by the indexing model from the issue text.

Description

MC 1.16-pre1 BackupList.func_230753_a_

...
      try {
         JsonElement jsonelement = jsonparser.parse(p_230753_0_).getAsJsonObject().get("backups");
         if (jsonelement.isJsonArray()) {
            Iterator<JsonElement> iterator = jsonelement.getAsJsonArray().iterator();

            while(iterator.hasNext()) {
               backuplist.field_230560_a_.add(Backup.func_230750_a_(iterator.next()));
            }
         }
      } catch (Exception exception) {
         field_230561_b_.error("Could not parse BackupList: " + exception.getMessage());
      }

      return backuplist;

There are a few cases like this. The enhanced for loop fails to generate as we expect the first statement in the loop to be iterator.next() being assigned to a variable. In this case, it has already been collapsed into the following statement.

I say this is a possible failure as the iterator variable definition has the correct generic type, which suggest the method was actually written this way.

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