When starting nix-shell for the second time, I get:
$ nix-shell
trace: No index state specified for nix-haskell-haskell-template, using the latest index state that we know about (2021-01-05T00:00:00Z)!trace: To make project.plan-nix for hoogle a fixed-output derivation but not materialized, set `plan-sha256` to the output of the 'calculateMaterializedSha' script in 'passthru'.
trace: To materialize project.plan-nix for hoogle entirely, pass a writable path as the `materialized` argument and run the 'updateMaterialized' script in 'passthru'.
trace: No index state specified for cabal-install, using the latest index state that we know about (2021-01-05T00:00:00Z)!
trace: No index state specified for ghcid, using the latest index state that we know about (2021-01-05T00:00:00Z)!
trace: To make project.plan-nix for haskell-language-server a fixed-output derivation but not materialized, set `plan-sha256` to the output of the 'calculateMaterializedSha' script in 'passthru'.
trace: To materialize project.plan-nix for haskell-language-server entirely, pass a writable path as the `materialized` argument and run the 'updateMaterialized' script in 'passthru'.
trace: No index state specified for ormolu, using the latest index state that we know about (2021-01-05T00:00:00Z)!
When starting nix-shell for the second time, I get: