[WIP] Implement pattern matching

fixtures/small/aryptn_actual.rb

@@ -0,0 +1,26 @@
+case ["I will arise", "and go now", "and go to Innisfree"]
+in String, String
+  "and a small cabin build there, of clay and wattles made"
+in SmallCabin["clay", "wattles"]
+  "Nine bean-rows will I have there, a hive for the honey-bee,"
+in BeeLoudGlade[String, *, String]
+  "And live alone in the bee-loud glade"
+end
+
+case ["And I shall have some peace there", "for peace", "comes dropping slow"]
+in String,;
+  "Dropping from the veils of the morning to where the cricket sings;"
+in Midnight[*glow]
+  "There midnight's all a glimmer, and noon a purple glow,"
+in 1, *, 2
+  "And evening full of the linnet's wings."
+end
+
+case []
+in [*]
+  0
+in []
+  1
+else
+  2
+end

fixtures/small/aryptn_expected.rb

@@ -0,0 +1,26 @@
+case ["I will arise", "and go now", "and go to Innisfree"]
+in [String, String]
+  "and a small cabin build there, of clay and wattles made"
+in SmallCabin["clay", "wattles"]
+  "Nine bean-rows will I have there, a hive for the honey-bee,"
+in BeeLoudGlade[String, *, String]
+  "And live alone in the bee-loud glade"
+end
+
+case ["And I shall have some peace there", "for peace", "comes dropping slow"]
+in [String, *]
+  "Dropping from the veils of the morning to where the cricket sings;"
+in Midnight[*glow]
+  "There midnight's all a glimmer, and noon a purple glow,"
+in [1, *, 2]
+  "And evening full of the linnet's wings."
+end
+
+case []
+in [*]
+  0
+in []
+  1
+else
+  2
+end

fixtures/small/fndptn_actual.rb

@@ -0,0 +1,7 @@
+case ["I will arise", "and go now", "for always night and day"]
+in Lake[*, "I hear lake water lapping",with_low_sounds_by_the_shore, *waves]
+    <<~YEATS
+        While I stand on the roadway, or on the pavements grey,
+        I hear it in the deep heart's core.
+    YEATS
+end

fixtures/small/fndptn_expected.rb

@@ -0,0 +1,7 @@
+case ["I will arise", "and go now", "for always night and day"]
+in Lake[*, "I hear lake water lapping", with_low_sounds_by_the_shore, *waves]
+  <<~YEATS
+    While I stand on the roadway, or on the pavements grey,
+    I hear it in the deep heart's core.
+  YEATS
+end

fixtures/small/hshptn_actual.rb

@@ -0,0 +1,22 @@
+case bees!
+in {}
+  ()
+in { bees: "bzzz" }
+  ()
+in { bees: "bzzz", **nil }
+  ()
+in bees:
+  ()
+in bees: this_is_a_bee
+    ()
+in Beehive(queen_bee:, drones:)
+  ()
+in Beehive(queen_bee:beyonce, drones:)
+  ()
+in Beehive(queen_bee:, **nil)
+  ()
+in Beehive(queen_bee:, **rest_of_the_hive)
+  ()
+in Beehive(queen_bee:, **)
+  ()
+end

fixtures/small/hshptn_expected.rb

@@ -0,0 +1,22 @@
+case bees!
+in {}
+  ()
+in {bees: "bzzz"}
+  ()
+in {bees: "bzzz", **nil}
+  ()
+in {bees:}
+  ()
+in {bees: this_is_a_bee}
+  ()
+in Beehive(queen_bee:, drones:)
+  ()
+in Beehive(queen_bee: beyonce, drones:)
+  ()
+in Beehive(queen_bee:, **nil)
+  ()
+in Beehive(queen_bee:, **rest_of_the_hive)
+  ()
+in Beehive(queen_bee:)
+  ()
+end

fixtures/small/multiline_aryptn_actual.rb

@@ -0,0 +1,8 @@
+case []
+in [first,
+  *,
+  last]
+  puts "bees!!!"
+else
+  "no bees"
+end

fixtures/small/multiline_aryptn_expected.rb

@@ -0,0 +1,10 @@
+case []
+in [
+    first,
+    *,
+    last
+  ]
+  puts("bees!!!")
+else
+  "no bees"
+end

fixtures/small/multiline_fndptn_actual.rb

@@ -0,0 +1,7 @@
+case []
+in *, "bees are present",
+  *; then
+  puts "bees!!!"
+else
+  "no bees"
+end

fixtures/small/multiline_fndptn_expected.rb

@@ -0,0 +1,10 @@
+case []
+in [
+    *,
+    "bees are present",
+    *
+  ]
+  puts("bees!!!")
+else
+  "no bees"
+end

fixtures/small/multiline_hshptn_actual.rb

@@ -0,0 +1,23 @@
+case bees!
+in {
+    bees: "bzzz"
+}
+  ()
+in {
+    bees: "bzzz",
+    **nil }
+  ()
+in bees:,
+    more_bees: aaaahhhh,;
+  ()
+in bees: this_is_a_bee
+    ()
+in Beehive(
+    queen_bee:,
+    drones:)
+  ()
+in Beehive(
+    queen_bee:,
+    **nil)
+  ()
+end

fixtures/small/multiline_hshptn_expected.rb

@@ -0,0 +1,28 @@
+case bees!
+in {
+    bees: "bzzz"
+  }
+  ()
+in {
+    bees: "bzzz",
+    **nil
+  }
+  ()
+in {
+    bees:,
+    more_bees: aaaahhhh
+  }
+  ()
+in {bees: this_is_a_bee}
+  ()
+in Beehive(
+    queen_bee:,
+    drones:
+  )
+  ()
+in Beehive(
+    queen_bee:,
+    **nil
+  )
+  ()
+end

librubyfmt/rubyfmt_lib.rb

@@ -44,6 +44,7 @@ def initialize(file_data)
       "next" => [],
       "return" => [],
       "when" => [],
+      "in" => [],
       "case" => [],
       "yield" => [],
       "break" => [],
@@ -374,6 +375,10 @@ def on_when(cond, body, tail)
     [:when, cond, body, tail, start_end_for_keyword('when')]
   end
 
+  def on_in(cond, body, tail)
+    [:in, cond, body, tail, start_end_for_keyword('in')]
+  end
+
   def on_case(cond, body)
     [:case, cond, body, start_end_for_keyword('case')]
   end
@@ -386,6 +391,45 @@ def on_break(arg)
     [:break, arg, start_end_for_keyword('break')]
   end
 
+  def on_var_field(ident)
+    # `ident` is `nil` for **nil in hshptn
+    line = if ident && ident != :nil
+      # ident.last = [line, col]
+      ident.last.first
+    else
+      # When ident is nil, this represents a "*" pattern, which
+      # is lexed as an op. *However*, this can also happen during
+      # an "implicit" splat, e.g. `in String,` (with a trailing comma),
+      # in which case there's not a last op_location either, so at that
+      # point we give up because `lineno` would be incorrect
+      #
+      # Important to note: in this case, we must `shift` and not `pop`,
+      # because in the case of fndptn, this isn't run until after both
+      # splats have been lexed, so their op locations will be in the reverse order
+      @op_locations.shift
+    end
+
+    start_end = if line
+      [[line, line]]
+    else
+      [nil]
+    end
+
+    super + start_end
+  end
+
+  def on_aryptn(*_)
+    with_lineno { super }
+  end
+
+  def on_fndptn(*_)
+    with_lineno { super }
+  end
+
+  def on_hshptn(*_)
+    with_lineno { super }
+  end
+
   def on_tlambda(*args)
     @tlambda_stack << lineno
     super