Got a bug to report. I haven't narrowed down a small case, but it's also not too large. I have one fathom file, Matrix.fan:

using [java] fanx.interop::DoubleArray as FloatArray

class Matrix {

  private FloatArray imag

  private Int m

  private Int n

  private FloatArray real

  new make(Num[][] rows := Float[][,]) {
    m = rows.size
    n = 0
    //rows.each |Num[] row| {
      // TODO Check for complex.
    //  n = n.max(row.size)
    //}
    echo(m)
    real = FloatArray(m * n)
    echo(real.size)
  }

}

And one test file:

class MatrixTest: Test {
  Void testAdd() {
    matrix := Matrix([
      [1, 2],
      [3, 4]
    ])
  }
}

And I get this error:

compile [fathom]
  Compile [fathom]
    FindSourceFiles [2 files]
    WritePod [/home/tom/Applications/fan-1.0.36/lib/fan/fathom.pod]
BUILD SUCCESS [2035ms]!

-- Run:  fathom::MatrixTest.testAdd...

TEST FAILED
sys::Err: java.lang.VerifyError: (class: fan/fathom/Matrix, method: make$ signature: (Lfan/fathom/Matrix;)V) Stack size too large
  fathom::MatrixTest.testAdd (MatrixTest.fan:5)
  sun.reflect.NativeMethodAccessorImpl.invoke0 (NativeMethodAccessorImpl.java)
  sun.reflect.NativeMethodAccessorImpl.invoke (NativeMethodAccessorImpl.java:39)
  sun.reflect.DelegatingMethodAccessorImpl.invoke (DelegatingMethodAccessorImpl.java:25)
  java.lang.reflect.Method.invoke (Method.java:597)
  fan.sys.Method.invoke (Method.java:558)
  fan.sys.Method$MethodFunc.call (Method.java:222)
  fan.sys.Method.call (Method.java:178)
  fanx.tools.Fant.runTest (Fant.java:171)
  ...

This is on Fan 1.0.36 on 32-bit Linux and Java 6.

Thanks for your bug report Tom.

It actually comes down to one line in how I was generating the wrappers for parameter defaults:

new make(Num[][] rows := Float[][,]) {}

I pushed a fix to hg and added a test for that case.

Thanks for the quick reply.

I've tested that this error is now fixed for me in 1.0.37.