8373570: Javac stack overflow on method-local class with nested record referring to enclosing type

[mcimadamore]

The fix for https://git.openjdk.org/jdk/pull/21410 introduced a regression: javac will no longer reject local classes created from a context that is not an inner class of the class enclosing the local class.

In other words, javac is failing to apply this restriction in the JLS (15.9.2):

If U is not an inner class of O or O itself, then a compile-time error occurs

The issue is causes by the new method Resolve::findLocalClassOwner. This method is meant to start at the point where the local class is instantiated, and walk up the enclosing scopes, until it finds the place where the local class is defined. If any static context has been traversed doing this search, an error is issued.

Unfortunately, neither static local classes, nor records/interfaces count as "static contexts" in the javac implementation -- that is, they do not increase the "static" counter in the env.info variable.

Instead, most code in Resolve does this (see e.g. Resolve::findFun):

while (env1.outer != null) {
    if (isStatic(env1)) staticOnly = true;
    ...
    if ((env1.enclClass.sym.flags() & STATIC) != 0) staticOnly = true;
    env1 = env1.outer;
}

The new method acts a bit differently, and it's missing the logic to check the staticness of the enclosing class, hence the regression.

---

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Issue

• JDK-8373570: Javac stack overflow on method-local class with nested record referring to enclosing type (Bug - P3)

Reviewers

• Vicente Romero (@vicente-romero-oracle - Reviewer)

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[mcimadamore]

In other similar loops, we would check isStatic as the first statement in the loop. However, here we can't do that -- if the local class is static, it will be defined in a static method -- this means the search will always end with a static context. But this is ok, and we don't want to raise an error!

[mcimadamore]

See tests staticLocal and staticLocalFromAnon (these were derived from some failing code in the Stream API).

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8373570: Javac stack overflow on method-local class with nested record referring to enclosing type

Reviewed-by: vromero

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At the time when this comment was updated there had been 137 new commits pushed to the master branch:

• 6aeabd4: 8370910: Cleanup terminology of UUID vs Global Identifiers in UUID
• f52d499: 8319589: Attach from root to a user java process not supported in Mac
• 45ee89c: 8373297: Test com/sun/jdi/AfterThreadDeathTest.java failed with unexpected ObjectCollectedException
• ... and 134 more: https://git.openjdk.org/jdk/compare/16699a394d4d6c2b8a21e7de3c3d344c5a3309b4...master

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[vicente-romero-oracle]

lgtm

[mcimadamore]

/integrate

[openjdk]

Going to push as commit 43d4456.
Since your change was applied there have been 143 commits pushed to the master branch:

• 8402891: 8373355: C2: CompileCommand PrintIdealPhase should also print nodes that are not "reachable from below"
• 78c2d57: 8373668: Add override keyword to *Klass classes
• b1e8c4e: 8372543: Shenandoah: undercalculated the available size when soft max takes effect
• ... and 140 more: https://git.openjdk.org/jdk/compare/16699a394d4d6c2b8a21e7de3c3d344c5a3309b4...master

Your commit was automatically rebased without conflicts.

[openjdk]

@mcimadamore Pushed as commit 43d4456.

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