Warning: The install command is a part of the legacy v1 style of cabal usage.

Please switch to using either the new project style and the new-install
command or the legacy v1-install alias as new-style projects will become the
default in the next version of cabal-install. Please file a bug if you cannot
replicate a working v1- use case with the new-style commands.

For more information, see: https://wiki.haskell.org/Cabal/NewBuild

Resolving dependencies...
cabal: Could not resolve dependencies:
[__0] trying: gi-gtk-declarative-app-simple-0.4.1 (user goal)
[__1] next goal: haskell-gi (dependency of gi-gtk-declarative-app-simple)
[__1] rejecting: haskell-gi-0.21.5, haskell-gi-0.21.4, haskell-gi-0.21.3,
haskell-gi-0.21.2, haskell-gi-0.21.1, haskell-gi-0.21.0 (conflict: pkg-config
package gobject-introspection-1.0>=1.32, not found in the pkg-config database)
[__1] rejecting: haskell-gi-0.20.3, haskell-gi-0.20.2, haskell-gi-0.20.1,
haskell-gi-0.20, haskell-gi-0.18, haskell-gi-0.17.4, haskell-gi-0.17.3,
haskell-gi-0.17.2, haskell-gi-0.17.1, haskell-gi-0.17, haskell-gi-0.15,
haskell-gi-0.14, haskell-gi-0.13, haskell-gi-0.12, haskell-gi-0.11,
haskell-gi-0.10.2, haskell-gi-0.10.1, haskell-gi-0.10, haskell-gi-0.9,
haskell-gi-0.8 (conflict: gi-gtk-declarative-app-simple => haskell-gi>=0.21 &&
<0.22)
[__1] fail (backjumping, conflict set: gi-gtk-declarative-app-simple,
haskell-gi)
After searching the rest of the dependency tree exhaustively, these were the
goals I've had most trouble fulfilling: haskell-gi,
gi-gtk-declarative-app-simple