Don't do a bogus substitution on the transformed self ty for objects. Closes #8664.

src/librustc/middle/typeck/check/method.rs

@@ -938,9 +938,18 @@ impl<'self> LookupContext<'self> {
 
         // static methods should never have gotten this far:
         assert!(candidate.method_ty.explicit_self != sty_static);
-        let transformed_self_ty =
-            ty::subst(tcx, &candidate.rcvr_substs,
-                      candidate.method_ty.transformed_self_ty.unwrap());
+
+        let transformed_self_ty = match candidate.origin {
+            method_object(*) => {
+                // For annoying reasons, we've already handled the
+                // substitution for object calls.
+                candidate.method_ty.transformed_self_ty.unwrap()
+            }
+            _ => {
+                ty::subst(tcx, &candidate.rcvr_substs,
+                          candidate.method_ty.transformed_self_ty.unwrap())
+            }
+        };
 
         // Determine the values for the type parameters of the method.
         // If they were not explicitly supplied, just construct fresh

src/test/run-pass/trait-object-generics.rs

@@ -8,6 +8,26 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
+// test for #8664
+
+pub trait Trait2<A> {
+    fn doit(&self);
+}
+
+pub struct Impl<A1, A2, A3> {
+    /*
+     * With A2 we get the ICE:
+     * task <unnamed> failed at 'index out of bounds: the len is 1 but the index is 1', /home/tortue/rust_compiler_newest/src/librustc/middle/subst.rs:58
+     */
+    t: ~Trait2<A2>
+}
+
+impl<A1, A2, A3> Impl<A1, A2, A3> {
+    pub fn step(&self) {
+        self.t.doit()
+    }
+}
+
 // test for #8601
 
 enum Type<T> { Constant }