Issue 1:
I got the compiler to panic. Here is the backtrace:

$ RUST_BACKTRACE=1 cargo build
Compiling mdbook v0.0.1 (file:///home/mathieu/Programming/Rust/mdbook)
error: internal compiler error: unexpected panic
note: the compiler unexpectedly panicked. this is a bug.
note: we would appreciate a bug report: https://github.com/rust-lang/rust/blob/master/CONTRIBUTING.md#bug-reports
thread 'rustc' panicked at 'fold_mac disabled by default', ../src/libsyntax/fold.rs:190

stack backtrace:
1: 0x7f8f9d556c8e - sys::backtrace::write::hba0090c65dc9b973kqs
2: 0x7f8f9d55eb34 - panicking::on_panic::ha888d43548c7ef7dU7w
3: 0x7f8f9d52168e - rt::unwind::begin_unwind_inner::h6c07c3faf8145c2ayNw
4: 0x7f8f9a83aba1 - rt::unwind::begin_unwind::h61311074365208902
5: 0x7f8f9aa98c31 - ptr::P<T>::map::h4262623173329566783
6: 0x7f8f9aa8953e - ext::expand::expand_expr::closure.64692
7: 0x7f8f9aa87344 - ext::expand::expand_expr::h5d16b298ec3e6d44S3a
8: 0x7f8f9aad6e3b - fold::noop_fold_stmt::h2830177968221966586
9: 0x7f8f9aab2f01 - ext::expand::expand_stmt::ha540a83711e3b587zEb
10: 0x7f8f9aadf7d3 - ext::expand::expand_block_elts::closure.65399
11: 0x7f8f9aadf4cc - iter::FlatMap<I, U, F>.Iterator::next::h15931703869202550713
12: 0x7f8f9aade2b7 - vec::Vec<T>.FromIterator<T>::from_iter::h17304921018562427167
13: 0x7f8f9aadd873 - ext::expand::expand_block_elts::closure.65393
14: 0x7f8f9aa9a5d6 - ext::expand::expand_block_elts::hdc0f023594f31dbdvPb
15: 0x7f8f9aadd57d - ext::expand::expand_block::h154763b840e3f863QOb
16: 0x7f8f9aa9a004 - ext::expand::expand_and_rename_fn_decl_and_block::he58b2e30da928a59Uic
17: 0x7f8f9ab05525 - ext::expand::expand_and_rename_method::he352edb1d6a5af96ekc
18: 0x7f8f9ab0a1cf - ext::expand::expand_impl_item::closure.65811
19: 0x7f8f9ab06c7f - ext::expand::expand_impl_item::hc5ab3bcbf3bfabe2Dfc
20: 0x7f8f9aa9db5e - ext::expand::expand_annotatable::h347111f998e00452RZb
21: 0x7f8f9aaacca5 - ext::expand::MacroExpander<'a, 'b>.Folder::fold_impl_item::h4b925cb3f2b4ecddKnc
22: 0x7f8f9aaac77d - iter::FlatMap<I, U, F>.Iterator::next::h10775116680282487154
23: 0x7f8f9aaaca53 - vec::Vec<T>::extend_desugared::h16127363502739536117
24: 0x7f8f9aaab6bf - iter::Iterator::collect::h10569062580348617273
25: 0x7f8f9aaa2597 - ext::expand::expand_item_underscore::h1ae9e40d706a69f4Zsb
26: 0x7f8f9ab047bd - fold::Folder::fold_item_simple::h13015839913330126400
27: 0x7f8f9ab043f4 - ptr::P<T>::map::h5783195092218359557
28: 0x7f8f9aa9e6c6 - ext::expand::expand_annotatable::h347111f998e00452RZb
29: 0x7f8f9aa9a728 - ext::expand::expand_item::h3529ff04c83295ccosb
30: 0x7f8f9aaa721e - iter::FlatMap<I, U, F>.Iterator::next::h3067849998977955174
31: 0x7f8f9aaa6007 - vec::Vec<T>.FromIterator<T>::from_iter::h17852130624423508185
32: 0x7f8f9aaa573c - fold::noop_fold_mod::h8231944226184386280
33: 0x7f8f9aaa1955 - ext::expand::expand_item_underscore::h1ae9e40d706a69f4Zsb
34: 0x7f8f9ab047bd - fold::Folder::fold_item_simple::h13015839913330126400
35: 0x7f8f9ab043f4 - ptr::P<T>::map::h5783195092218359557
36: 0x7f8f9aa9f127 - ext::expand::expand_annotatable::h347111f998e00452RZb
37: 0x7f8f9aa9a728 - ext::expand::expand_item::h3529ff04c83295ccosb
38: 0x7f8f9aaa721e - iter::FlatMap<I, U, F>.Iterator::next::h3067849998977955174
39: 0x7f8f9aaa5cf4 - vec::Vec<T>.FromIterator<T>::from_iter::h17852130624423508185
40: 0x7f8f9aaa573c - fold::noop_fold_mod::h8231944226184386280
41: 0x7f8f9aaa1955 - ext::expand::expand_item_underscore::h1ae9e40d706a69f4Zsb
42: 0x7f8f9ab047bd - fold::Folder::fold_item_simple::h13015839913330126400
43: 0x7f8f9ab043f4 - ptr::P<T>::map::h5783195092218359557
44: 0x7f8f9aa9f127 - ext::expand::expand_annotatable::h347111f998e00452RZb
45: 0x7f8f9aa9a728 - ext::expand::expand_item::h3529ff04c83295ccosb
46: 0x7f8f9aaa721e - iter::FlatMap<I, U, F>.Iterator::next::h3067849998977955174
47: 0x7f8f9aaa6007 - vec::Vec<T>.FromIterator<T>::from_iter::h17852130624423508185
48: 0x7f8f9aaa573c - fold::noop_fold_mod::h8231944226184386280
49: 0x7f8f9aaa1955 - ext::expand::expand_item_underscore::h1ae9e40d706a69f4Zsb
50: 0x7f8f9ab047bd - fold::Folder::fold_item_simple::h13015839913330126400
51: 0x7f8f9ab043f4 - ptr::P<T>::map::h5783195092218359557
52: 0x7f8f9aa9f127 - ext::expand::expand_annotatable::h347111f998e00452RZb
53: 0x7f8f9aa9a728 - ext::expand::expand_item::h3529ff04c83295ccosb
54: 0x7f8f9ab0d5b9 - ext::expand::expand_crate::hffd65e9f8234e652prc
55: 0x7f8f9daf3a1d - driver::phase_2_configure_and_expand::closure.21446
56: 0x7f8f9daa56dc - driver::phase_2_configure_and_expand::h6227118d5a2dbd5dita
57: 0x7f8f9da94a3a - driver::compile_input::ha9b5fd65b77d50f6Tba
58: 0x7f8f9db72863 - run_compiler::h240fdc5369e0b898x7b
59: 0x7f8f9db7023e - boxed::F.FnBox<A>::call_box::h17338777036410156156
60: 0x7f8f9db6fa89 - rt::unwind::try::try_fn::h2295644814600911096
61: 0x7f8f9d5d6d38 - rust_try_inner
62: 0x7f8f9d5d6d25 - rust_try
63: 0x7f8f9d549ee7 - rt::unwind::try::inner_try::h3a5b73fc117bcddfrJw
64: 0x7f8f9db6fc9b - boxed::F.FnBox<A>::call_box::h803341546616928030
65: 0x7f8f9d55d791 - sys::thread::Thread::new::thread_start::h780a1f33992577dcoTv
66: 0x7f8f97bef353 - start_thread
67: 0x7f8f9d1b8bfc - __clone
68: 0x0 - <unknown>

This is the part of my code that made the compiler panic:

fn parse_summary(&mut self) -> Result<()> {
let summary = BufReader::new(try!(File::open(self.config.src().join("SUMMARY.md"))));

let mut level = -1;
for try!(line) in summary.lines() {
let indent = utilities::indent(&line, 4);

// If the difference between the current level and the indent level is greater than
// one then there is a syntax error in SUMMARY.md
/*if i32::abs(level - indent) > 1 {
return Error::new(ErrorKind::Other,"Indentation error in SUMMARY.md at line:\n\n")
}*/
}

Ok(())
}

If I comment out the body of the function it works.

Info about my machine:

Arch Linux
cargo 0.3.0-nightly (a2dd2ac 2015-06-24) (built 2015-06-23)
rustc 1.2.0-beta.1 (2ad26e850 2015-06-23)

I am not sure what info you need, so tell me if I forgot something or you want more code.

Issue 2:
macro_rules! foo {
() => ()
}

pub fn main () {
for foo!() in (1..) {
}
}

error:

error: internal compiler error: unexpected panic
note: the compiler unexpectedly panicked. this is a bug.
note: we would appreciate a bug report: https://github.com/rust-lang/rust/blob/master/CONTRIBUTING.md#bug-reports
note: run with `RUST_BACKTRACE=1` for a backtrace
thread 'rustc' panicked at 'fold_mac disabled by default', /home/rustbuild/src/rust-buildbot/slave/stable-dist-rustc-linux/build/src/libsyntax/fold.rs:190

playpen: application terminated with error code 101

version is whatever is considered stable by play.rust-lang.org at 3:30pm UTC+12 13/07/2015, but also for the nightly and beta releases.