1 files changed, 76 insertions, 0 deletions
diff --git a/pkgs/stdenv/generic/meta-types.nix b/pkgs/stdenv/generic/meta-types.nix
new file mode 100644
index 0000000000000..ddbd1daca696e
--- /dev/null
+++ b/pkgs/stdenv/generic/meta-types.nix
@@ -0,0 +1,76 @@
+{ lib }:
+# Simple internal type checks for meta.
+# This file is not a stable interface and may be changed arbitrarily.
+#
+# TODO: add a method to the module system types
+#       see https://github.com/NixOS/nixpkgs/pull/273935#issuecomment-1854173100
+let
+  inherit (builtins) isString isInt isAttrs isList all any attrValues isFunction isBool concatStringsSep isFloat;
+  isTypeDef = t: isAttrs t && t ? name && isString t.name && t ? verify && isFunction t.verify;
+
+in
+lib.fix (self: {
+  string = {
+    name = "string";
+    verify = isString;
+  };
+  str = self.string;  # Type alias
+
+  any = {
+    name = "any";
+    verify = _: true;
+  };
+
+  int = {
+    name = "int";
+    verify = isInt;
+  };
+
+  float = {
+    name = "float";
+    verify = isFloat;
+  };
+
+  bool = {
+    name = "bool";
+    verify = isBool;
+  };
+
+  attrs = {
+    name = "attrs";
+    verify = isAttrs;
+  };
+
+  list = {
+    name = "list";
+    verify = isList;
+  };
+
+  attrsOf = t: assert isTypeDef t; let
+    inherit (t) verify;
+  in {
+    name = "attrsOf<${t.name}>";
+    verify =
+      # attrsOf<any> can be optimised to just isAttrs
+      if t == self.any then isAttrs
+      else attrs: isAttrs attrs && all verify (attrValues attrs);
+  };
+
+  listOf = t: assert isTypeDef t; let
+    inherit (t) verify;
+  in {
+    name = "listOf<${t.name}>";
+    verify =
+      # listOf<any> can be optimised to just isList
+      if t == self.any then isList
+      else v: isList v && all verify v;
+  };
+
+  union = types: assert all isTypeDef types; let
+    # Store a list of functions so we don't have to pay the cost of attrset lookups at runtime.
+    funcs = map (t: t.verify) types;
+  in {
+    name = "union<${concatStringsSep "," (map (t: t.name) types)}>";
+    verify = v: any (func: func v) funcs;
+  };
+})