Index strings through checker-any receivers (#1965)

packages/compiler/src/frontend/lowering/expressions/element-access.ts

@@ -566,8 +566,8 @@ export function lowerElementAccess(lowerer: Lowerer, expr: ts.ElementAccessExpre
     }
   }
   if (receiverIr?.kind !== "array") {
+    const receiver = tryLowerExpression(lowerer, expr.expression);
     {
-      const receiver = tryLowerExpression(lowerer, expr.expression);
       if (
         receiver?.type.kind === "dyn" ||
         (receiver &&
@@ -618,7 +618,13 @@ export function lowerElementAccess(lowerer: Lowerer, expr: ts.ElementAccessExpre
         }
       }
     }
-    if (receiverIr?.kind === "string") {
+    // A checker-`any` receiver that lowers to a string (an implicit-any
+    // package parameter specialized for a string argument) indexes the
+    // string the same way.
+    if (
+      receiverIr?.kind === "string" ||
+      (receiverIr === null && receiver?.type.kind === "string")
+    ) {
       // An indexed string property is absent for non-integer and missing
       // indexes. charAt has different coercion and out-of-range semantics.
       const recv = lowerer.lowerExpr(expr.expression);

packages/compiler/test/ts7/baselines/order-parity/tests/corpus/7731-npm-any-string-index/main.ts.json

@@ -0,0 +1,6 @@
+{
+ "order": [
+  "<repo>/tests/corpus/7731-npm-any-string-index/main.ts"
+ ],
+ "diags": []
+}

tests/corpus/7731-npm-any-string-index/main.ts

@@ -0,0 +1,9 @@
+// An implicit-any package function specialized for a string argument indexes
+// the string (`base?.[0]`), as hono's mergePath does.
+import { App, mergePath } from "merge-path";
+console.log(new App().request("x"));
+console.log(new App().request(new URL("http://h/p")));
+console.log(new App().basePath("/api").basePath("v1/")._basePath);
+console.log(mergePath("/api/", "/"), mergePath("a", "b", "/c"));
+console.log(new App().basePath("").basePath("").request(""));
+console.log(mergePath("", "x"), mergePath("/", "/"), mergePath("//", "y/"));

tests/corpus/7731-npm-any-string-index/node_modules/merge-path/index.d.ts

@@ -0,0 +1,2 @@
+export declare const mergePath: (...paths: string[]) => string;
+export declare class App { _basePath: string; request: (input: string | URL) => string; basePath(path: string): App; }

tests/corpus/7731-npm-any-string-index/node_modules/merge-path/index.js

@@ -0,0 +1,10 @@
+import { mergePath } from "./url.js";
+class App {
+  _basePath = "/";
+  request = (input) => {
+    input = input.toString();
+    return mergePath("/", input);
+  };
+  basePath(path) { const s = new App(); s._basePath = mergePath(this._basePath, path); return s; }
+}
+export { App, mergePath };

tests/corpus/7731-npm-any-string-index/node_modules/merge-path/package.json

@@ -0,0 +1 @@
+{ "name": "merge-path", "version": "1.0.0", "type": "module", "main": "index.js", "types": "index.d.ts" }

tests/corpus/7731-npm-any-string-index/node_modules/merge-path/url.js

@@ -0,0 +1,10 @@
+/**
+* Merge paths.
+* @param {string[]} ...paths - The paths to merge.
+* @returns {string} The merged path.
+*/
+const mergePath = (base, sub, ...rest) => {
+  if (rest.length) sub = mergePath(sub, ...rest);
+  return `${base?.[0] === "/" ? "" : "/"}${base}${sub === "/" ? "" : `${base?.[base.length - 1] === "/" ? "" : "/"}${sub?.[0] === "/" ? sub.slice(1) : sub}`}`;
+};
+export { mergePath };

tests/harness/corpus-costs/7731-npm-any-string-index/main.ts.json

@@ -0,0 +1 @@
+{ "plain": 6200, "san": 5800 }