Fix missing error for function call spread in iterator parameter validation

Co-authored-by: andrewbranch <[email protected]>

Author: Copilot

internal/checker/checker.go

@@ -5905,7 +5905,10 @@ func (c *Checker) getIterationTypesOfIterable(t *Type, use IterationUse, errorNo
 		return cached
 	}
 	result := c.getIterationTypesOfIterableWorker(t, use, errorNode)
-	c.iterationTypesCache[key] = result
+	// Don't cache empty results when error reporting is requested, to ensure errors are reported for each call site
+	if result.hasTypes() || errorNode == nil {
+		c.iterationTypesCache[key] = result
+	}
 	return result
 }
 

testdata/baselines/reference/submodule/compiler/iteratorExtraParameters.errors.txt

@@ -1,9 +1,10 @@
 iteratorExtraParameters.ts(11,21): error TS2488: Type '{ [Symbol.iterator](_: number): Generator<number, void, unknown>; }' must have a '[Symbol.iterator]()' method that returns an iterator.
 iteratorExtraParameters.ts(13,12): error TS2488: Type '{ [Symbol.iterator](_: number): Generator<number, void, unknown>; }' must have a '[Symbol.iterator]()' method that returns an iterator.
 iteratorExtraParameters.ts(15,9): error TS2488: Type '{ [Symbol.iterator](_: number): Generator<number, void, unknown>; }' must have a '[Symbol.iterator]()' method that returns an iterator.
+iteratorExtraParameters.ts(17,10): error TS2488: Type '{ [Symbol.iterator](_: number): Generator<number, void, unknown>; }' must have a '[Symbol.iterator]()' method that returns an iterator.
 
 
-==== iteratorExtraParameters.ts (3 errors) ====
+==== iteratorExtraParameters.ts (4 errors) ====
     // https://github.com/microsoft/TypeScript/issues/57130
     const iter = {
         *[Symbol.iterator](_: number) {
@@ -39,5 +40,11 @@ iteratorExtraParameters.ts(15,9): error TS2488: Type '{ [Symbol.iterator](_: num
       Target signature provides too few arguments. Expected 1 or more, but got 0.
 
         g(...iter);
+             ~~~~
+!!! error TS2488: Type '{ [Symbol.iterator](_: number): Generator<number, void, unknown>; }' must have a '[Symbol.iterator]()' method that returns an iterator.
+!!! related TS2322 iteratorExtraParameters.ts:17:10: Type '{ [Symbol.iterator](_: number): Generator<number, void, unknown>; }' is not assignable to type 'Iterable<T, TReturn, TNext>'.
+  Types of property '[Symbol.iterator]' are incompatible.
+    Type '(_: number) => Generator<number, void, unknown>' is not assignable to type '() => Iterator<T, TReturn, TNext>'.
+      Target signature provides too few arguments. Expected 1 or more, but got 0.
     }
 

testdata/baselines/reference/submodule/compiler/iteratorExtraParameters.errors.txt.diff

@@ -1,9 +1,10 @@
 omittedExpressionForOfLoop.ts(1,19): error TS2304: Cannot find name 'doesNotExist'.
 omittedExpressionForOfLoop.ts(4,19): error TS18050: The value 'undefined' cannot be used here.
 omittedExpressionForOfLoop.ts(7,12): error TS2488: Type 'never' must have a '[Symbol.iterator]()' method that returns an iterator.
+omittedExpressionForOfLoop.ts(10,12): error TS2488: Type 'never' must have a '[Symbol.iterator]()' method that returns an iterator.
 
 
-==== omittedExpressionForOfLoop.ts (3 errors) ====
+==== omittedExpressionForOfLoop.ts (4 errors) ====
     for (const [,] of doesNotExist) {
                       ~~~~~~~~~~~~
 !!! error TS2304: Cannot find name 'doesNotExist'.
@@ -20,4 +21,6 @@ omittedExpressionForOfLoop.ts(7,12): error TS2488: Type 'never' must have a '[Sy
     }
 
     for (const [] of []) {
+               ~~
+!!! error TS2488: Type 'never' must have a '[Symbol.iterator]()' method that returns an iterator.
     }

testdata/baselines/reference/submodule/compiler/omittedExpressionForOfLoop.errors.txt

@@ -1,7 +1,8 @@
 for-of16.ts(8,11): error TS2488: Type 'MyStringIterator' must have a '[Symbol.iterator]()' method that returns an iterator.
+for-of16.ts(10,11): error TS2488: Type 'MyStringIterator' must have a '[Symbol.iterator]()' method that returns an iterator.
 
 
-==== for-of16.ts (1 errors) ====
+==== for-of16.ts (2 errors) ====
     class MyStringIterator {
         [Symbol.iterator]() {
             return this;
@@ -14,4 +15,7 @@ for-of16.ts(8,11): error TS2488: Type 'MyStringIterator' must have a '[Symbol.it
 !!! error TS2488: Type 'MyStringIterator' must have a '[Symbol.iterator]()' method that returns an iterator.
 !!! related TS2489 for-of16.ts:8:11: An iterator must have a 'next()' method.
 
-    for (v of new MyStringIterator) { } // Should still fail (related errors should still be shown even though type is cached).
+    for (v of new MyStringIterator) { } // Should still fail (related errors should still be shown even though type is cached).
+              ~~~~~~~~~~~~~~~~~~~~
+!!! error TS2488: Type 'MyStringIterator' must have a '[Symbol.iterator]()' method that returns an iterator.
+!!! related TS2489 for-of16.ts:10:11: An iterator must have a 'next()' method.

testdata/baselines/reference/submodule/compiler/omittedExpressionForOfLoop.errors.txt.diff

@@ -3,9 +3,10 @@ types.forAwait.es2018.2.ts(8,21): error TS2504: Type '{}' must have a '[Symbol.a
 types.forAwait.es2018.2.ts(10,16): error TS2322: Type 'number' is not assignable to type 'string'.
 types.forAwait.es2018.2.ts(12,16): error TS2322: Type 'number' is not assignable to type 'string'.
 types.forAwait.es2018.2.ts(14,21): error TS2488: Type 'AsyncIterable<number>' must have a '[Symbol.iterator]()' method that returns an iterator.
+types.forAwait.es2018.2.ts(16,15): error TS2488: Type 'AsyncIterable<number>' must have a '[Symbol.iterator]()' method that returns an iterator.
 
 
-==== types.forAwait.es2018.2.ts (5 errors) ====
+==== types.forAwait.es2018.2.ts (6 errors) ====
     declare const asyncIterable: AsyncIterable<number>;
     declare const iterable: Iterable<number>;
     async function f() {
@@ -33,6 +34,9 @@ types.forAwait.es2018.2.ts(14,21): error TS2488: Type 'AsyncIterable<number>' mu
 !!! related TS2773 types.forAwait.es2018.2.ts:14:21: Did you forget to use 'await'?
         }
         for (y of asyncIterable) {
+                  ~~~~~~~~~~~~~
+!!! error TS2488: Type 'AsyncIterable<number>' must have a '[Symbol.iterator]()' method that returns an iterator.
+!!! related TS2773 types.forAwait.es2018.2.ts:16:15: Did you forget to use 'await'?
         }
     }