lib.types: add luaInline

Represents inline lua as expected by `lib.generators.toLua`, for
embedding raw lua expressions within structurally generated lua.

lib/types.nix

@@ -834,6 +834,15 @@ rec {
         };
       };
 
+    # A value produced by `lib.mkLuaInline`
+    luaInline = mkOptionType {
+      name = "luaInline";
+      description = "inline lua";
+      descriptionClass = "noun";
+      check = x: x._type or null == "lua-inline";
+      merge = mergeEqualOption;
+    };
+
     uniq = unique { message = ""; };
 
     unique = { message }: type: mkOptionType rec {

nixos/doc/manual/development/option-types.section.md

@@ -232,6 +232,13 @@ merging is handled.
     definitions cannot be merged. The regular expression is processed
     using `builtins.match`.
 
+### Specialised types {#sec-option-types-specialised}
+
+`types.luaInline`
+
+:   A string wrapped using `lib.mkLuaInline`. Allows embedding lua expressions
+    inline within generated lua. Multiple definitions cannot be merged.
+
 ## Submodule types {#sec-option-types-submodule}
 
 Submodules are detailed in [Submodule](#section-option-types-submodule).

nixos/doc/manual/redirects.json

@@ -1592,6 +1592,9 @@
   "sec-option-types-string": [
     "index.html#sec-option-types-string"
   ],
+  "sec-option-types-specialised": [
+    "index.html#sec-option-types-specialised"
+  ],
   "sec-option-types-submodule": [
     "index.html#sec-option-types-submodule"
   ],