From f0b67b59fdbc2bcebd60f311af716c617724022e Mon Sep 17 00:00:00 2001
From: Pierre-Antoine Mills <pierreantoine.urvoy@gmail.com>
Date: Fri, 4 Oct 2019 16:10:25 +0200
Subject: [PATCH 1/4] test: recursive iteration types for ts-toolbelt

---
 tests/cases/user/ts-toolbelt/index.ts      | 29 ++++++++++++++++++++++
 tests/cases/user/ts-toolbelt/package.json  | 14 +++++++++++
 tests/cases/user/ts-toolbelt/tsconfig.json |  5 ++++
 3 files changed, 48 insertions(+)
 create mode 100644 tests/cases/user/ts-toolbelt/index.ts
 create mode 100644 tests/cases/user/ts-toolbelt/package.json
 create mode 100644 tests/cases/user/ts-toolbelt/tsconfig.json

diff --git a/tests/cases/user/ts-toolbelt/index.ts b/tests/cases/user/ts-toolbelt/index.ts
new file mode 100644
index 0000000000000..7b20589ad66fd
--- /dev/null
+++ b/tests/cases/user/ts-toolbelt/index.ts
@@ -0,0 +1,29 @@
+import {I, T, Test} from "ts-toolbelt";
+
+const {check, checks} = Test;
+
+// iterates over `T` and returns the `Iteration` position when finished
+type RecursiveIteration<T extends any[], I extends I.Iteration = I.IterationOf<'0'>> = {
+    0: RecursiveIteration<T, I.Next<I>>;
+    1: I.Pos<I>;
+}[
+    T.Length<T> extends I.Pos<I>
+    ? 1
+    : 0
+];
+
+checks([
+    check<RecursiveIteration<[
+        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
+    check<RecursiveIteration<[
+        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,
+    ]>, number, Test.Pass>() // it overflowed
+]);
diff --git a/tests/cases/user/ts-toolbelt/package.json b/tests/cases/user/ts-toolbelt/package.json
new file mode 100644
index 0000000000000..d066aeec2d688
--- /dev/null
+++ b/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"
+  }
+}
diff --git a/tests/cases/user/ts-toolbelt/tsconfig.json b/tests/cases/user/ts-toolbelt/tsconfig.json
new file mode 100644
index 0000000000000..fc0c19189c360
--- /dev/null
+++ b/tests/cases/user/ts-toolbelt/tsconfig.json
@@ -0,0 +1,5 @@
+{
+    "compilerOptions": {
+        "strict": true
+    }
+}

From 2ace88eb123844fef25772253c03383ff98754fa Mon Sep 17 00:00:00 2001
From: Pierre-Antoine Mills <pierreantoine.urvoy@gmail.com>
Date: Sat, 5 Oct 2019 14:04:22 +0200
Subject: [PATCH 2/4] fix: implementation details

---
 tests/cases/user/ts-toolbelt/index.ts | 31 +++++++++++++++++++--------
 1 file changed, 22 insertions(+), 9 deletions(-)

diff --git a/tests/cases/user/ts-toolbelt/index.ts b/tests/cases/user/ts-toolbelt/index.ts
index 7b20589ad66fd..8f71a933bbc9d 100644
--- a/tests/cases/user/ts-toolbelt/index.ts
+++ b/tests/cases/user/ts-toolbelt/index.ts
@@ -3,27 +3,40 @@ import {I, T, Test} from "ts-toolbelt";
 const {check, checks} = Test;
 
 // iterates over `T` and returns the `Iteration` position when finished
-type RecursiveIteration<T extends any[], I extends I.Iteration = I.IterationOf<'0'>> = {
-    0: RecursiveIteration<T, I.Next<I>>;
+type StdRecursiveIteration<T extends any[], I extends I.Iteration = I.IterationOf<'0'>> = {
+    0: StdRecursiveIteration<T, I.Next<I>>;
     1: I.Pos<I>;
 }[
-    T.Length<T> extends I.Pos<I>
-    ? 1
-    : 0
-];
+    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 swallowed by type atm)
 
 checks([
-    check<RecursiveIteration<[
+    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
-    check<RecursiveIteration<[
+]);
+
+// 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,
-    ]>, number, Test.Pass>() // it overflowed
+    ]>, 0, Test.Pass>() // did not compute
 ]);

From 2bdd6a9760514f2e3af5069849f60b5876e8b3a5 Mon Sep 17 00:00:00 2001
From: Pierre-Antoine Mills <pierreantoine.urvoy@gmail.com>
Date: Sat, 5 Oct 2019 14:05:42 +0200
Subject: [PATCH 3/4] fix: comment

---
 tests/cases/user/ts-toolbelt/index.ts | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/tests/cases/user/ts-toolbelt/index.ts b/tests/cases/user/ts-toolbelt/index.ts
index 8f71a933bbc9d..054d707911178 100644
--- a/tests/cases/user/ts-toolbelt/index.ts
+++ b/tests/cases/user/ts-toolbelt/index.ts
@@ -10,7 +10,7 @@ type StdRecursiveIteration<T extends any[], I extends I.Iteration = I.IterationO
     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 swallowed by type atm)
+];                               // (but error is sometimes swallowed (?))
 
 checks([
     check<StdRecursiveIteration<[

From 8422362f061caad257949c7275164e71f1963ad7 Mon Sep 17 00:00:00 2001
From: Pierre-Antoine Mills <pierreantoine.urvoy@gmail.com>
Date: Wed, 16 Oct 2019 01:47:32 +0200
Subject: [PATCH 4/4] Update index.ts

---
 tests/cases/user/ts-toolbelt/index.ts | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/tests/cases/user/ts-toolbelt/index.ts b/tests/cases/user/ts-toolbelt/index.ts
index 054d707911178..218db6ba38dc0 100644
--- a/tests/cases/user/ts-toolbelt/index.ts
+++ b/tests/cases/user/ts-toolbelt/index.ts
@@ -1,3 +1,5 @@
+// ! this library is mostly used with ramda
+
 import {I, T, Test} from "ts-toolbelt";
 
 const {check, checks} = Test;