# Herbert Wolverson - Rust Brain Teasers (Highlights) ![rw-book-cover|256](https://readwise-assets.s3.amazonaws.com/media/reader/parsed_document_assets/326398656/klZA2xAfqpzl9vpY70f-RLF7D8OuFAyC7KJID1ZGoqA-cove_bCOed9b.jpg) ## Metadata **Review**:: [readwise.io](https://readwise.io/bookreview/52698936) **Source**:: #from/readwise #from/reader **Zettel**:: #zettel/fleeting **Status**:: #x **Authors**:: [[Herbert Wolverson]] **Full Title**:: Rust Brain Teasers **Category**:: #books #readwise/books **Category Icon**:: 📚 **Highlighted**:: [[2025-06-22]] **Created**:: [[2025-06-28]] ## Highlights - When used with an as keyword, _ indicates that Rust should try to convert the value into whatever type is expected in this context. For example, function_that_requires_a_u32(x as _) will try to convert x—irrespective of its type—to a u32. ([View Highlight](https://read.readwise.io/read/01jycpcp1s1qq2dv1n63q8jehm)) ^905957047 - As it turns out, for loops fall into the unavailable category because they require a Range—prohibited because of the generic bounds restriction. This makes the example code fail to compile. ([View Highlight](https://read.readwise.io/read/01jycqa71epbgfqx4bwqftqc2g)) ^905962043 for is not allowed in a const fn