unison/unison-src/transcripts/suffixes.md

Suffix-based resolution of names

scratch/main> builtins.merge

Any unique name suffix can be used to refer to a definition. For instance:

-- No imports needed even though FQN is `builtin.{Int,Nat}`
foo.bar.a : Int
foo.bar.a = +99

-- No imports needed even though FQN is `builtin.Optional.{None,Some}`
optional.isNone = cases
  None -> true
  Some _ -> false

This also affects commands like find. Notice lack of qualified names in output:

scratch/main> add
scratch/main> find take

The view and display commands also benefit from this:

scratch/main> view List.drop
scratch/main> display bar.a

In the signature, we don't see base.Nat, just Nat. The full declaration name is still shown for each search result though.

Type-based search also benefits from this, we can just say Nat rather than .base.Nat:

scratch/main> find : Nat -> [a] -> [a]

Preferring names not in lib.*.lib.*

Suffix-based resolution prefers names that are not in an indirect dependency.

cool.abra.cadabra = "my project"
lib.distributed.abra.cadabra = "direct dependency 1"
lib.distributed.baz.qux = "direct dependency 2"
lib.distributed.lib.baz.qux = "indirect dependency"

scratch/main> add

> abra.cadabra

> baz.qux

scratch/main> view abra.cadabra
scratch/main> view baz.qux

Note that we can always still view indirect dependencies by using more name segments:

scratch/main> view distributed.abra.cadabra
scratch/main> names distributed.lib.baz.qux

Corner cases

If a definition is given in a scratch file, its suffixes shadow existing definitions that exist in the codebase with the same suffixes. For example:

unique type A = Thing1 Nat | thing2 Nat

foo.a = 23
bar = 100

scratch/main> add

unique type B = Thing1 Text | thing2 Text | Thing3 Text

zoink.a = "hi"

-- verifying that the `a` here references `zoink.a`
foo.baz.qux.bar : Text
foo.baz.qux.bar = a

-- verifying that the `bar` is resolving to `foo.baz.qux.bar`
-- and that `Thing1` references `B.Thing1` from the current file
fn = cases
  Thing1 msg -> msg Text.++ bar
  thing2 msg -> msg Text.++ bar
  _ -> todo "hmm"