Normative: iterator-producing helpers close receiver on argument validation failure

Author: bakkot

spec.html

@@ -46759,11 +46759,17 @@ <h1>Iterator.prototype.drop ( _limit_ )</h1>
         <emu-alg>
           1. Let _O_ be the *this* value.
           1. If _O_ is not an Object, throw a *TypeError* exception.
-          1. Let _numLimit_ be ? ToNumber(_limit_).
-          1. If _numLimit_ is *NaN*, throw a *RangeError* exception.
+          1. Let _iterated_ be the Iterator Record { [[Iterator]]: _O_, [[NextMethod]]: *undefined*, [[Done]]: *false* }.
+          1. Let _numLimit_ be Completion(ToNumber(_limit_)).
+          1. IfAbruptCloseIterator(_numLimit_, _iterated_).
+          1. If _numLimit_ is *NaN*, then
+            1. Let _error_ be ThrowCompletion(a newly created *RangeError* object).
+            1. Return ? IteratorClose(_iterated_, _error_).
           1. Let _integerLimit_ be ! ToIntegerOrInfinity(_numLimit_).
-          1. If _integerLimit_ &lt; 0, throw a *RangeError* exception.
-          1. Let _iterated_ be ? GetIteratorDirect(_O_).
+          1. If _integerLimit_ &lt; 0, then
+            1. Let _error_ be ThrowCompletion(a newly created *RangeError* object).
+            1. Return ? IteratorClose(_iterated_, _error_).
+          1. Set _iterated_ to ? GetIteratorDirect(_O_).
           1. Let _closure_ be a new Abstract Closure with no parameters that captures _iterated_ and _integerLimit_ and performs the following steps when called:
             1. Let _remaining_ be _integerLimit_.
             1. Repeat, while _remaining_ > 0,
@@ -46807,8 +46813,11 @@ <h1>Iterator.prototype.filter ( _predicate_ )</h1>
         <emu-alg>
           1. Let _O_ be the *this* value.
           1. If _O_ is not an Object, throw a *TypeError* exception.
-          1. If IsCallable(_predicate_) is *false*, throw a *TypeError* exception.
-          1. Let _iterated_ be ? GetIteratorDirect(_O_).
+          1. Let _iterated_ be the Iterator Record { [[Iterator]]: _O_, [[NextMethod]]: *undefined*, [[Done]]: *false* }.
+          1. If IsCallable(_predicate_) is *false*, then
+            1. Let _error_ be ThrowCompletion(a newly created *TypeError* object).
+            1. Return ? IteratorClose(_iterated_, _error_).
+          1. Set _iterated_ to ? GetIteratorDirect(_O_).
           1. Let _closure_ be a new Abstract Closure with no parameters that captures _iterated_ and _predicate_ and performs the following steps when called:
             1. Let _counter_ be 0.
             1. Repeat,
@@ -46851,8 +46860,11 @@ <h1>Iterator.prototype.flatMap ( _mapper_ )</h1>
         <emu-alg>
           1. Let _O_ be the *this* value.
           1. If _O_ is not an Object, throw a *TypeError* exception.
-          1. If IsCallable(_mapper_) is *false*, throw a *TypeError* exception.
-          1. Let _iterated_ be ? GetIteratorDirect(_O_).
+          1. Let _iterated_ be the Iterator Record { [[Iterator]]: _O_, [[NextMethod]]: *undefined*, [[Done]]: *false* }.
+          1. If IsCallable(_mapper_) is *false*, then
+            1. Let _error_ be ThrowCompletion(a newly created *TypeError* object).
+            1. Return ? IteratorClose(_iterated_, _error_).
+          1. Set _iterated_ to ? GetIteratorDirect(_O_).
           1. Let _closure_ be a new Abstract Closure with no parameters that captures _iterated_ and _mapper_ and performs the following steps when called:
             1. Let _counter_ be 0.
             1. Repeat,
@@ -46905,8 +46917,11 @@ <h1>Iterator.prototype.map ( _mapper_ )</h1>
         <emu-alg>
           1. Let _O_ be the *this* value.
           1. If _O_ is not an Object, throw a *TypeError* exception.
-          1. If IsCallable(_mapper_) is *false*, throw a *TypeError* exception.
-          1. Let _iterated_ be ? GetIteratorDirect(_O_).
+          1. Let _iterated_ be the Iterator Record { [[Iterator]]: _O_, [[NextMethod]]: *undefined*, [[Done]]: *false* }.
+          1. If IsCallable(_mapper_) is *false*, then
+            1. Let _error_ be ThrowCompletion(a newly created *TypeError* object).
+            1. Return ? IteratorClose(_iterated_, _error_).
+          1. Set _iterated_ to ? GetIteratorDirect(_O_).
           1. Let _closure_ be a new Abstract Closure with no parameters that captures _iterated_ and _mapper_ and performs the following steps when called:
             1. Let _counter_ be 0.
             1. Repeat,
@@ -46973,11 +46988,17 @@ <h1>Iterator.prototype.take ( _limit_ )</h1>
         <emu-alg>
           1. Let _O_ be the *this* value.
           1. If _O_ is not an Object, throw a *TypeError* exception.
-          1. Let _numLimit_ be ? ToNumber(_limit_).
-          1. If _numLimit_ is *NaN*, throw a *RangeError* exception.
+          1. Let _iterated_ be the Iterator Record { [[Iterator]]: _O_, [[NextMethod]]: *undefined*, [[Done]]: *false* }.
+          1. Let _numLimit_ be Completion(ToNumber(_limit_)).
+          1. IfAbruptCloseIterator(_numLimit_, _iterated_).
+          1. If _numLimit_ is *NaN*, then
+            1. Let _error_ be ThrowCompletion(a newly created *RangeError* object).
+            1. Return ? IteratorClose(_iterated_, _error_).
           1. Let _integerLimit_ be ! ToIntegerOrInfinity(_numLimit_).
-          1. If _integerLimit_ &lt; 0, throw a *RangeError* exception.
-          1. Let _iterated_ be ? GetIteratorDirect(_O_).
+          1. If _integerLimit_ &lt; 0, then
+            1. Let _error_ be ThrowCompletion(a newly created *RangeError* object).
+            1. Return ? IteratorClose(_iterated_, _error_).
+          1. Set _iterated_ to ? GetIteratorDirect(_O_).
           1. Let _closure_ be a new Abstract Closure with no parameters that captures _iterated_ and _integerLimit_ and performs the following steps when called:
             1. Let _remaining_ be _integerLimit_.
             1. Repeat,