Add TypeNode#[] when T is a tuple type

crystal-lang · Jun 3, 2016 · 5fc4f1a · 5fc4f1a
1 parent 8bfa519
commit 5fc4f1a
Showing 2 changed files with 26 additions and 2 deletions.
diff --git a/spec/compiler/type_inference/tuple_spec.cr b/spec/compiler/type_inference/tuple_spec.cr
@@ -208,4 +208,15 @@ describe "Type inference: tuples" do
       Tuple(Int32, String).types
       )) { tuple_of([int32.metaclass, string.metaclass]) }
   end
+
+  it "can call [] on T" do
+    assert_type(%(
+      struct Tuple
+        def self.types
+          {{ T[0] }}
+        end
+      end
+      Tuple(Nil, Int32).types
+      )) { |mod| mod.nil.metaclass }
+  end
 end
diff --git a/src/compiler/crystal/macros/methods.cr b/src/compiler/crystal/macros/methods.cr
@@ -955,7 +955,8 @@ module Crystal
       when "[]"
         interpret_one_arg_method(method, args) do |arg|
           type = type.instance_type
-          if type.is_a?(NamedTupleInstanceType)
+          case type
+          when NamedTupleInstanceType
             case arg
             when SymbolLiteral
               key = arg.value
@@ -969,8 +970,20 @@ module Crystal
               return NilLiteral.new
             end
             TypeNode.new(type.entries[index].type)
+          when TupleInstanceType
+            case arg
+            when NumberLiteral
+              index = arg.to_number.to_i
+              type = type.tuple_types[index]?
+              unless type
+                return NilLiteral.new
+              end
+              TypeNode.new(type)
+            else
+              return NilLiteral.new
+            end
           else
-            raise "undefined method '[]' for TypeNode of type #{type} (must be a named tuple type)"
+            raise "undefined method '[]' for TypeNode of type #{type} (must be a tuple or named tuple type)"
           end
         end
       when "class"