added example from reddit

examples/expr-dot-where.ts.md

@@ -0,0 +1,27 @@
+## `expr-dot-where.ts`
+
+### Status: `DONE`
+
+### Input Program
+
+```typescript
+// from https://www.reddit.com/r/ProgrammingLanguages/comments/1gyo9hm/dear_language_designers_please_copy_where_from/
+// from https://kiru.io/blog/posts/2024/dear-language-designers-please-copy-where-from-haskell/
+
+using_syntax_rules(
+  [where, expr.where(a = b, rest), ((a) => expr.where(rest))(b)],
+  [where, expr.where(a = b),       ((a) => expr)(b)],
+  [where, expr.where(),            expr],
+).rewrite(
+
+  (x + y).where(x = 1, y = x + 2)
+
+);
+```
+
+### Output Program
+
+```typescript
+((x_6) => ((y_10) => x_6 + y_10)(x_6 + 2))(1);
+```
+

src/parse.ts

@@ -5,7 +5,6 @@ import TS, { SyntaxKind } from "typescript";
 import { assert } from "./assert";
 
 const pass_through: { [k in SyntaxKind]?: list_tag } = {
-  [SyntaxKind.CallExpression]: "call_expression",
   [SyntaxKind.ParenthesizedExpression]: "parenthesized_expression",
   [SyntaxKind.BinaryExpression]: "binary_expression",
   [SyntaxKind.PrefixUnaryExpression]: "unary_expression",
@@ -102,6 +101,15 @@ function absurdly(node: TS.Node, src: TS.SourceFile): AST {
           return { type: "list", tag: "ERROR", content };
         }
       }
+      case SyntaxKind.CallExpression: {
+        assert(ls.length === 4, ls);
+        assert(ls[2].tag === "syntax_list");
+        return {
+          type: "list",
+          tag: "call_expression",
+          content: [ls[0], [ls[1], llappend(ls[2].content, [ls[3], null])]],
+        };
+      }
       case SyntaxKind.ArrowFunction: {
         assert(ls.length === 5, ls);
         const [lt, fmls, rt, ar, body] = ls;

tests/expr-dot-where.ts

@@ -0,0 +1,12 @@
+// from https://www.reddit.com/r/ProgrammingLanguages/comments/1gyo9hm/dear_language_designers_please_copy_where_from/
+// from https://kiru.io/blog/posts/2024/dear-language-designers-please-copy-where-from-haskell/
+
+using_syntax_rules(
+  [where, expr.where(a = b, rest), ((a) => expr.where(rest))(b)],
+  [where, expr.where(a = b),       ((a) => expr)(b)],
+  [where, expr.where(),            expr],
+).rewrite(
+
+  (x + y).where(x = 1, y = x + 2)
+
+);