type_checkers: argument

Author: krishpranav

src/type_checkers/argument.cr

@@ -0,0 +1,49 @@
+# -----------------------------------------------------------------------
+# This file is part of MoonScript
+#
+# MoonSript is free software: you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation, either version 3 of the License, or
+# (at your option) any later version.
+#
+# MoonSript is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with MoonSript.  If not, see <https://www.gnu.org/licenses/>.
+#
+# Copyright (C) 2025 Krisna Pranav, MoonScript Developers
+# -----------------------------------------------------------------------
+
+module MoonScript
+  class TypeChecker
+    def check(node : Ast::Argument) : Checkable
+      default =
+        node.default.try(&->resolve(Ast::Node))
+
+      type =
+        resolve_type(resolve(node.type))
+          .tap(&.label = node.name.try(&.value))
+
+      case {default, type}
+      in {Checkable, Checkable}
+        resolved =
+          Comparer.compare type, default
+
+        error! :argument_type_mismatch do
+          block "The type of the default value of an argument does not " \
+                "match type"
+
+          expected type, default
+          snippet "The argument is here:", node
+        end unless resolved
+
+        type
+      in {Nil, Checkable}
+        type
+      end
+    end
+  end
+end