RFR: 8317336: Assertion error thrown during 'this' escape analysis [v5]

[Archie Cobbs]

On Wed, 11 Oct 2023 00:51:49 GMT, Archie Cobbs <acobbs at openjdk.org> wrote:

>> The 'this' escape analyzer was assuming that lambas could always be treated like blocks, in the sense that we can assume a block can never end in a plain expression. This assumption is not true for lambda's of the form `() -> foo` which do exactly that. In the case that `foo` was `this`, an assertion failure would ensue.
>> 
>> This patch explicitly clears any leftover `ExprRef`'s after evaluating a lambda body; this restores the asserted invariant when the lambda body is an expression.
>> 
>> This also fixes another variant of the same bug caused by certain enhanced `for()` loops. In this case, the leftover `ExprRef` was from evaluating the loop expression. This was just a side-effect of the analyzer failing to override `TreeScanner` to actually assign the loop expression to the loop variable (that will be fixed later in another patch).
>
> Archie Cobbs has updated the pull request incrementally with three additional commits since the last revision:
> 
>  - Fix regression test class names.
>  - Refactor patch to minimize it to just the required bugfix.
>  - Fix inadvertent variable renaming.

@vicente-romero-oracle, thanks for the reviews.

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PR Comment: https://git.openjdk.org/jdk/pull/16001#issuecomment-1758472743