feat: string interpolation

Author: mhanberg

lib/spitfire.ex

@@ -571,6 +571,32 @@ defmodule Spitfire do
     {string, parser}
   end
 
+  defp parse_string(%{current_token: {:bin_string, _, tokens}} = parser) do
+    args =
+      for token <- tokens do
+        case token do
+          token when is_binary(token) ->
+            token
+
+          {_start, _stop, tokens} ->
+            # construct a new parser
+            parser = %{
+              tokens: tokens ++ [:eof],
+              current_token: nil,
+              peek_token: nil,
+              nestings: [],
+              stab_depth: 0
+            }
+
+            {ast, _parser} = parse_expression(parser |> next_token() |> next_token())
+
+            {:"::", [], [{{:., [], [Kernel, :to_string]}, [], [ast]}, {:binary, [], Elixir}]}
+        end
+      end
+
+    {{:<<>>, [], args}, parser}
+  end
+
   defp parse_alias(%{current_token: {:alias, _, alias}} = parser) do
     aliases = [alias]
 

test/spitfire_test.exs

@@ -50,6 +50,24 @@ defmodule SpitfireTest do
     assert Spitfire.parse(code) == "foobar"
   end
 
+  test "parses string interpolation" do
+    code = ~S'''
+    "foo#{alice}bar"
+    '''
+
+    assert Spitfire.parse(code) ==
+             {:<<>>, [],
+              [
+                "foo",
+                {:"::", [],
+                 [
+                   {{:., [], [Kernel, :to_string]}, [], [{:alice, [], Elixir}]},
+                   {:binary, [], Elixir}
+                 ]},
+                "bar"
+              ]}
+  end
+
   test "parses atoms" do
     code = ~s'''
     :foobar