RFR: 8293578: Duplicate ldc generated by javac

[Maurizio Cimadamore]

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.

Looks good

test/langtools/tools/javac/lvti/ConstantTypes.java line 99:

> 97:     }
> 98: 
> 99: }

watch out for newline

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Marked as reviewed by mcimadamore (Reviewer).

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