Allow calling the result of a function call

lib/ahem/parser.rb

@@ -284,17 +284,19 @@ class Parser
         raise "Unexpected token #{token.type}"
       end
 
-    if @current_token.type == TokenKinds::LPAREN
+    while @current_token.type == TokenKinds::LPAREN
       args = arguments
-      AST::FunctionCall.new(expr, args)
-    elsif @current_token.type == TokenKinds::LBRACKET
+      expr = AST::FunctionCall.new(expr, args)
+    end
+
+    while @current_token.type == TokenKinds::LBRACKET
       eat(TokenKinds::LBRACKET)
       key = expression
       eat(TokenKinds::RBRACKET)
-      AST::Index.new(expr, key)
-    else
-      expr
+      expr = AST::Index.new(expr, key)
     end
+
+    expr
   end
 
   def function_expression

spec/parser_spec.rb

@@ -454,4 +454,18 @@ RSpec.describe Parser do
       [AST::Assignment.new(AST::Identifier.new('x'), AST::Number.new(5.0))]
     )
   end
+
+  it 'allows calling the result of a function call as a function' do
+    expect(parse('func()();')).to eq(
+      [
+        AST::FunctionCall.new(
+          AST::FunctionCall.new(
+            AST::Identifier.new('func'),
+            [],
+          ),
+          []
+        )        
+      ]
+    )
+  end
 end