Hi, I propose adding an `Access.at!` that raises when the given index is out of bounds, analogous to `Access.key!`.
The current `Access.at` is not nil safe as discussed in https://groups.google.com/g/elixir-lang-core/c/CvdW1FsvSf0/m/nlvxkThuEwAJ, but it's also not analogous to `Access.key!`. I specifically want it to raise and point to being out of range (or whatever the terminology is), rather than causing nil errors further down the line. Current behaviour with `Access.at`: # Happy case. Everything exists. iex(20)> get_in([%{key: "value"}], [Access.at(0), :key]) "value" # Nil safe when index is out of bounds. iex(21)> get_in([%{key: "value"}], [Access.at(1), :key]) nil # Not nil safe, but error doesn't point to the array index. iex(22)> get_in([%{key: "value"}], [Access.at(1), Access.key!(:key)]) ** (RuntimeError) Access.key!/1 expected a map/struct, got: nil (elixir 1.10.3) lib/access.ex:514: anonymous fn/4 in Access.key!/1 I propose something like this behaviour, with `Access.at!`: # Happy case – behaves the same. iex(20)> get_in([%{key: "value"}], [Access.at!(0), :key]) "value" # Explodes. iex(21)> get_in([%{key: "value"}], [Access.at!(1), :key]) ** (FooError) index 1 not found in: [%{key: "value"}]. Its highest index is 0. # Explodes in the same way. iex(22)> get_in([%{key: "value"}], [Access.at(1), Access.key!(:key)]) ** (FooError) index 1 not found in: [%{key: "value"}]. Its highest index is 0. What do you think? -- You received this message because you are subscribed to the Google Groups "elixir-lang-core" group. To unsubscribe from this group and stop receiving emails from it, send an email to elixir-lang-core+unsubscr...@googlegroups.com. To view this discussion on the web visit https://groups.google.com/d/msgid/elixir-lang-core/3a5d1489-dfa5-4c0c-bcd1-5cb85eac2f3fn%40googlegroups.com.
