Support demangling symbols with dot-delimited words at the end

This accounts for values like LLVM IR branch labels.

Closes #15

Author: shepmaster

src/lib.rs

@@ -36,6 +36,7 @@ use core::fmt;
 pub struct Demangle<'a> {
     original: &'a str,
     inner: &'a str,
+    suffix: &'a str,
     valid: bool,
     /// The number of ::-separated elements in the original name.
     elements: usize,
@@ -98,6 +99,15 @@ pub fn demangle(mut s: &str) -> Demangle {
         }
     }
 
+    // Output like LLVM IR adds extra period-delimited words. See if
+    // we are in that case and save the trailing words if so.
+    let mut suffix = "";
+    if let Some(i) = s.rfind("E.") {
+        let (head, tail) = s.split_at(i + 1); // After the E, before the period
+        s = head;
+        suffix = tail;
+    }
+
     // First validate the symbol. If it doesn't look like anything we're
     // expecting, we just print it literally. Note that we must handle non-Rust
     // symbols because we could have any function in the backtrace.
@@ -155,6 +165,7 @@ pub fn demangle(mut s: &str) -> Demangle {
 
     Demangle {
         inner: inner,
+        suffix: suffix,
         valid: valid,
         elements: elements,
         original: s,
@@ -288,6 +299,8 @@ impl<'a> fmt::Display for Demangle<'a> {
             }
         }
 
+        try!(f.write_str(self.suffix));
+
         Ok(())
     }
 }
@@ -398,6 +411,12 @@ mod tests {
         t_nohash!("_ZN9backtrace3foo17hbb467fcdaea5d79bE.llvm.A5310EB9", "backtrace::foo");
     }
 
+    #[test]
+    fn demangle_llvm_ir_branch_labels() {
+        t!("_ZN4core5slice77_$LT$impl$u20$core..ops..index..IndexMut$LT$I$GT$$u20$for$u20$$u5b$T$u5d$$GT$9index_mut17haf9727c2edfbc47bE.exit.i.i", "core::slice::<impl core::ops::index::IndexMut<I> for [T]>::index_mut::haf9727c2edfbc47b.exit.i.i");
+        t_nohash!("_ZN4core5slice77_$LT$impl$u20$core..ops..index..IndexMut$LT$I$GT$$u20$for$u20$$u5b$T$u5d$$GT$9index_mut17haf9727c2edfbc47bE.exit.i.i", "core::slice::<impl core::ops::index::IndexMut<I> for [T]>::index_mut.exit.i.i");
+    }
+
     #[test]
     fn dont_panic() {
         super::demangle("_ZN2222222222222222222222EE").to_string();