Use 'unreachable' to silence clippy on route codegen.

Closes #794.

core/codegen/Cargo.toml

@@ -32,4 +32,4 @@ rev = "62f361f"
 
 [dev-dependencies]
 rocket = { version = "0.4.0-dev", path = "../lib" }
-compiletest_rs = { version = "0.3", features = ["stable"] }
+compiletest_rs = { git = "https://github.com/laumann/compiletest-rs" }

core/codegen/src/attribute/route.rs

@@ -180,9 +180,11 @@ fn data_expr(ident: &syn::Ident, ty: &syn::Type) -> TokenStream2 {
             Owned(Outcome::Success(__v)) => Owned(Outcome::Success(__v)),
             Borrowed(Outcome::Success(ref __v)) => {
                 Borrowed(Outcome::Success(::std::borrow::Borrow::borrow(__v)))
-            }
-            Borrowed(__o) => Borrowed(__o.map(|_| loop { /* unreachable */ })),
-            Owned(__o) => Owned(__o)
+            },
+            Borrowed(__o) => Borrowed(__o.map(|_| {
+                unreachable!("Borrowed(Success(..)) case handled in previous block")
+            })),
+            Owned(__o) => Owned(__o),
         };
 
         #[allow(non_snake_case, unreachable_patterns, unreachable_code)]