Integrated: 8293578: Duplicate ldc generated by javac

[Jan Lahoda]

On Wed, 14 Sep 2022 17:15:30 GMT, Jan Lahoda <jlahoda at openjdk.org> wrote:

> Consider code like:
> 
> var testC = "incorrect".getClass();
> var testV = testC.getConstructor(String.class)
>                            .newInstance("correct");
> System.err.println(testV);
> 
> 
> javac has a concept of types with attached constants (to support proper behavior of constant expressions). Normally, these constants are cleared as specific places. But, in the above case, the type of `testC` is actually `Class<? extends String["incorrect"]>`, the constant then gets propagated, and eventually the type of `testV` is `String["incorrect"]`, and the code generator will then replace reads from `testV` with a ldc for the constant, so the code above prints "incorrect" instead of "correct".
> 
> The solution is to invoke `.baseType()` to remove the constant value when constructing the synthetic `.getClass()`'s type (so the type of `testC` is `Class<? extends String>`), and also a tweak to `checkLocalVarType`, as suggested in the bug.

This pull request has now been integrated.

Changeset: 39cd1635
Author:    Jan Lahoda <jlahoda at openjdk.org>
URL:       https://git.openjdk.org/jdk/commit/39cd1635bf07f42857e1a704734db66b2c2fa882
Stats:     103 lines in 3 files changed: 99 ins; 0 del; 4 mod

8293578: Duplicate ldc generated by javac

Reviewed-by: mcimadamore

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PR: https://git.openjdk.org/jdk/pull/10272