RFR: 8334043: VerifyError when inner class is accessed in prologue

[Archie Cobbs]

On Tue, 11 Jun 2024 21:10:37 GMT, Archie Cobbs <acobbs at openjdk.org> wrote:

> The new flexible constructors logic creates an exception to the normal rule preventing early access to `this` in an early construction context by allowing assignments to instance fields. The check for this exception is performed by `Resolve.isAllowedEarlyReference()`, but this method was incorrectlly assuming that the expression was simpler than it can sometimes be, for example, for more complicated assignment expressions like `this.new InnerClass().foo = 123`.
> 
> This change verifies that the expression actually looks like either `Y = Z` or `X.Y = Z` where `X` is a simple reference to the current class' `this` instance (i.e., `this`, or `ThisClass.this`).

> The fix seems too strict? E.g. something like this is legal, I believe:
> 
> ```java
> class A {
>    Object o;
>    A() { A.this.o = "Hello"; }
> }
> ```

That compiles, and so does this (which puts the assignment in an early construction context):


class A {
  Object o;
  A() {
    A.this.o = "Hello";
    super();
  }
}


If you're getting at the `A.this` vs. `this` question, that's what `TreeInfo.isExplicitThisReference()` is there to handle.

I could be missing what you're getting at, if so let me know.

-------------

PR Comment: https://git.openjdk.org/jdk/pull/19666#issuecomment-2163391100