Support let..in

samples/let-in.nix

@@ -0,0 +1 @@
+let x = { a = 1; b = x.a + 1; c = x.b + 1; }; in x.c

src/prepare-ast.js

@@ -108,6 +108,7 @@ function convertNode(node) {
 		parenthesized: "NixParenthesizedExpression",
 		attrset: "NixAttributeSet",
 		rec_attrset: "NixAttributeSet",
+		let: "NixLetIn",
 		identifier: "NixIdentifier",
 		attr_identifier: "NixAttributeIdentifier",
 		attrpath: "NixAttributePath",

src/transformers/_nix-types.js

@@ -40,5 +40,12 @@ let types = module.exports = {
 			type: "NixAttributeIdentifier",
 			name: name
 		};
+	},
+	NixAttributeSelection: function (expression, attributePath) {
+		return {
+			type: "NixAttributeSelection",
+			attrpath: types.NixAttributePath(attributePath),
+			expression: expression
+		};
 	}
 };

src/transformers/index.js

@@ -100,6 +100,7 @@ let trivial = {
 };
 
 module.exports = [
+	require("./let-in"),
 	require("./desugar-attrsets"),
 	require("./literals"),
 	require("./functions"),

src/transformers/let-in.js

@@ -0,0 +1,21 @@
+"use strict";
+
+const nixTypes = require("./_nix-types");
+
+module.exports = {
+	name: "let-in",
+	visitors: {
+		NixLetIn: (node) => {
+			return nixTypes.NixAttributeSelection(
+				nixTypes.NixAttributeSet([
+					... node.bind,
+					nixTypes.NixBinding(
+						[ nixTypes.NixAttributeIdentifier("$$jsNix$letBody") ],
+						node.body
+					)
+				], true),
+				[ nixTypes.NixAttributeIdentifier("$$jsNix$letBody") ]
+			);
+		}
+	}
+};