dhall 1.20.0 (new formula)

Closes #34157.

Signed-off-by: Igor Kapkov <igasgeek@me.com>

Formula/dhall.rb

@@ -0,0 +1,23 @@
+require "language/haskell"
+
+class Dhall < Formula
+  include Language::Haskell::Cabal
+
+  desc "Interpreter for the Dhall language"
+  homepage "https://dhall-lang.org/"
+  url "https://hackage.haskell.org/package/dhall-1.20.0/dhall-1.20.0.tar.gz"
+  sha256 "662862e65e73de18c01001e0ab43af155d111631ad12d14d89ec37d1397ccf43"
+
+  depends_on "cabal-install" => :build
+  depends_on "ghc" => :build
+
+  def install
+    install_cabal_package
+  end
+
+  test do
+    assert_match "{=}", pipe_output("#{bin}/dhall format", "{ = }", 0)
+    assert_match "8", pipe_output("#{bin}/dhall normalize", "(\\(x : Natural) -> x + 3) 5", 0)
+    assert_match "∀(x : Natural) → Natural", pipe_output("#{bin}/dhall type", "\\(x: Natural) -> x + 3", 0)
+  end
+end