test(ts-toolbelt): recursive iteration types (#33810)

* test: recursive iteration types for ts-toolbelt

* fix: implementation details

* fix: comment

* Update index.ts

Author: millsp

tests/cases/user/ts-toolbelt/index.ts

@@ -0,0 +1,44 @@
+// ! this library is mostly used with ramda
+
+import {I, T, Test} from "ts-toolbelt";
+
+const {check, checks} = Test;
+
+// iterates over `T` and returns the `Iteration` position when finished
+type StdRecursiveIteration<T extends any[], I extends I.Iteration = I.IterationOf<'0'>> = {
+    0: StdRecursiveIteration<T, I.Next<I>>;
+    1: I.Pos<I>;
+}[
+    I.Pos<I> extends T.Length<T> // this form of recursion is preferred
+    ? 1                          // because it will let the user know if                   
+    : 0                          // the instantiation depth has been hit
+];                               // (but error is sometimes swallowed (?))
+
+checks([
+    check<StdRecursiveIteration<[
+        0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
+        0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
+        0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
+        0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
+    ]>, 40, Test.Pass>(), // max length is 40
+]);
+
+// iterates over `T` and returns the `Iteration` position when finished
+type SafeRecursiveIteration<T extends any[], I extends I.Iteration = I.IterationOf<'0'>> = {
+    0: SafeRecursiveIteration<T, I.Next<I>>;
+    1: I.Pos<I>;
+}[
+    I.Key<I> extends T.Length<T, 's'> // this form of recursion is the safest
+    ? 1                               // because `T.Length<T, 's'>` will force
+    : 0                               // the length to comply with the limits
+];                                    // => won't compute if excessive length                           
+
+checks([
+    check<SafeRecursiveIteration<[
+        0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
+        0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
+        0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
+        0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
+        0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
+    ]>, 0, Test.Pass>() // did not compute
+]);

tests/cases/user/ts-toolbelt/package.json

@@ -0,0 +1,14 @@
+{
+  "name": "ts-toolbelt-test",
+  "version": "1.0.0",
+  "description": "",
+  "author": "",
+  "license": "Apache-2.0",
+  "repository":  {
+    "type": "git",
+    "url": "https://github.com/pirix-gh/ts-toolbelt"
+  },
+  "dependencies": {
+    "ts-toolbelt": "latest"
+  }
+}

tests/cases/user/ts-toolbelt/tsconfig.json

@@ -0,0 +1,5 @@
+{
+    "compilerOptions": {
+        "strict": true
+    }
+}