rollup merge of #18398 : aturon/lint-conventions-2

Conflicts:
	src/libcollections/slice.rs
	src/libcore/failure.rs
	src/libsyntax/parse/token.rs
	src/test/debuginfo/basic-types-mut-globals.rs
	src/test/debuginfo/simple-struct.rs
	src/test/debuginfo/trait-pointers.rs
rollup merge of #18430 : bjz/token

Conflicts:
	src/libsyntax/parse/parser.rs
rollup merge of #18445 : alexcrichton/index-mut

Conflicts:
	src/libcollections/vec.rs
Test fixes and rebase conflicts