SI-10032 Fix code gen with returns in nested try-finally blocks

Return statements within `try` or `catch` blocks need special treatement
if there's also a `finally`

    try { return 1 } finally { println() }

For the return, the code generator emits a store to a local and a jump
to a "cleanup" version of the finally block. There will be 3 versions
of the finally block:

  - One reached through a handler, if the code in the try block
    throws; re-throws at the end
  - A "cleanup" version reached from returns within the try; reads the
    local and returns the value at the end
  - One reached for ordinary control flow, if there's no return and no
    exception within the try

If there are multiple enclosing finally blocks, a "cleanup" version is
emitted for each of them. The nested ones jump to the enclosing ones,
the outermost one reads the local and returns.

A global variable `shouldEmitCleanup` stores whether cleanup versions
are required for the curren finally blocks. By mistake, this variable
was not reset to `false` when emitting a `try-finally` nested within a
`finally`:

    try {
      try { return 1 }
      finally { println() } // need cleanup version
    } finally {             // need cleanup version
      try { println() }
      finally { println() } // no cleanup version needed!
    }

In this commit we ensure that the variable is reset when emitting
nested `try-finally` blocks.

1 files changed, 49 insertions, 0 deletions

diff --git a/test/files/run/t10032.check b/test/files/run/t10032.check
new file mode 100644
index 0000000000..c8f0bdf034
--- /dev/null
+++ b/test/files/run/t10032.check
@@ -0,0 +1,49 @@
+t10032.scala:72: warning: Return statement found in finally-clause, discarding its return-value in favor of that of a more deeply nested return.
+      finally { return i2 }
+                ^
+t1
+ i1
+ a1
+t2
+ i1
+ a1
+ a2
+ a3
+t3
+ i1
+ a1
+ a3
+t3
+ e1
+ a1
+ i2
+ a2
+ a3
+t4
+ i1
+ i2
+t5
+ i1
+ a1
+ a3
+t5
+ e1
+ a1
+ i2
+ a3
+t6
+ i1
+ i2
+ i3
+t7
+ i1
+ a1
+t7
+ e1
+ i2
+ a1
+t8
+ i1
+ i2
+ a1
+ a2