Warn if non-trivial work is done inside .expect

- added tests for common usages of format and as_str arguments to expect
- added tests for usages of Option and Result types
- given performance impact of passing non literal expressions to expect, added to perf group

clippy_lints/src/lib.rs

@@ -590,6 +590,7 @@ pub fn register_plugins(reg: &mut rustc_plugin::Registry) {
         methods::OK_EXPECT,
         methods::OPTION_MAP_OR_NONE,
         methods::OR_FUN_CALL,
+        methods::EXPECT_FUN_CALL,
         methods::SEARCH_IS_SOME,
         methods::SHOULD_IMPLEMENT_TRAIT,
         methods::SINGLE_CHAR_PATTERN,
@@ -899,6 +900,7 @@ pub fn register_plugins(reg: &mut rustc_plugin::Registry) {
         loops::UNUSED_COLLECT,
         methods::ITER_NTH,
         methods::OR_FUN_CALL,
+        methods::EXPECT_FUN_CALL,
         methods::SINGLE_CHAR_PATTERN,
         misc::CMP_OWNED,
         mutex_atomic::MUTEX_ATOMIC,