Redeclaring a method resets dependent variable values

[m-dzianishchyts]

Summary

Redeclaring a method resets the value of variables that depend on the previous method implementation.

Steps to Reproduce

Execute the following snippet:

int f() { return 1; }
var v = f();

int f() { return 2; }
v;

Expected Behavior

The value of v should remain unchanged after f() is redeclared:

1

v was initialized using the original implementation of f(), so redefining f() should not retroactively re-evaluate or reset v.

jshell cli tool handles this.

Actual Behavior

After redeclaring f(), evaluating v returns:

0

The original value is lost.

Root Cause

When f() is redeclared, JShell recompiles both the method wrapper and dependent variable wrapper. JJava does not support in-place redefinitions, so JShell falls back to replacement wrapper classes.

The replacement wrapper for v is loaded with its static backing field in the default state. Since the variable initializer is not re-executed during dependent recompilation, v becomes the default value instead of retaining its original value.

Possible Solution

Implement true in-place class redefinition (jshell approach) by providing a real ExecutionControl.redefine() implementation so existing wrapper classes retain their identity and static field values while receiving updated method bytecode.