internal compiler error: debuginfo::create_for_loop_var_metadata()

[ngsankha]

I was working on a Rust project at sankha93/numrs and the source builds fine with Cargo on my machine but I just added Travis CI support and this is the error I get on their workers.

src/solver.rs:4:7: 4:8 warning: unused variable: `i`, #[warn(unused_variables)] on by default
src/solver.rs:4   for i in range(0, iter) {
                      ^
src/solver.rs:4:7: 4:8 warning: unused variable: `i`, #[warn(unused_variables)] on by default
src/solver.rs:4   for i in range(0, iter) {
                      ^
src/matrix.rs:46:11: 46:12 error: internal compiler error: debuginfo::create_for_loop_var_metadata() - Referenced variable location is not an alloca!
src/matrix.rs:46       for i in range(0, self.num_rows()) {
                           ^
note: the compiler unexpectedly panicked. this is a bug.
note: we would appreciate a bug report: http://doc.rust-lang.org/complement-bugreport.html
note: run with `RUST_BACKTRACE=1` for a backtrace
thread 'rustc' panicked at 'Box<Any>', /home/rustbuild/src/rust-buildbot/slave/nightly-linux/build/src/libsyntax/diagnostic.rs:123

The entire log can be found here: https://travis-ci.org/sankha93/numrs/builds/44855056

[alexcrichton]

Dupe of #20127, but thanks for the report!