iter: expose fundamental types to Go 1.23

These were previously only available with GOEXPERIMENT=rangefunc.

For #61897.

Change-Id: I86aea5ae8be1f7a2975b623325811221ed40d384
Reviewed-on: https://go-review.googlesource.com/c/go/+/557836
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Reviewed-by: Alan Donovan <adonovan@google.com>

api/next/61897.txt

@@ -0,0 +1,4 @@
+pkg iter, func Pull2[$0 interface{}, $1 interface{}](Seq2[$0, $1]) (func() ($0, $1, bool), func()) #61897
+pkg iter, func Pull[$0 interface{}](Seq[$0]) (func() ($0, bool), func()) #61897
+pkg iter, type Seq2[$0 interface{}, $1 interface{}] func(func($0, $1) bool) #61897
+pkg iter, type Seq[$0 interface{}] func(func($0) bool) #61897

doc/next/6-stdlib/3-iter.md

@@ -0,0 +1,4 @@
+### Iterators
+
+The new [`iter` package](/pkg/iter/) provides the basic definitions for
+working with user-defined iterators.

doc/next/6-stdlib/99-minor/iter/61897.md

@@ -0,0 +1 @@
+<!-- see ../../3-iter.md -->

src/go/build/deps_test.go

@@ -85,11 +85,9 @@ var depsRules = `
 	< internal/reflectlite
 	< errors
 	< internal/oserror, math/bits
+	< iter
 	< RUNTIME;
 
-	internal/race
-	< iter;
-
 	# slices depends on unsafe for overlapping check, cmp for comparison
 	# semantics, and math/bits for # calculating bitlength of numbers.
 	unsafe, cmp, math/bits
@@ -389,7 +387,6 @@ var depsRules = `
 	internal/nettrace,
 	internal/poll,
 	internal/singleflight,
-	internal/race,
 	net/netip,
 	os
 	< net;

src/go/doc/comment/std.go

@@ -23,6 +23,7 @@ var stdPkgs = []string{
 	"html",
 	"image",
 	"io",
+	"iter",
 	"log",
 	"maps",
 	"math",

src/iter/iter.go

@@ -2,13 +2,8 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
-//go:build goexperiment.rangefunc
-
 // Package iter provides basic definitions and operations
 // related to iteration in Go.
-//
-// This package is experimental and can only be imported
-// when building with GOEXPERIMENT=rangefunc.
 package iter
 
 import (

src/iter/pull_test.go

@@ -2,12 +2,11 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
-//go:build goexperiment.rangefunc
+package iter_test
-
-package iter
 
 import (
 	"fmt"
+	. "iter"
 	"runtime"
 	"testing"
 )
@@ -33,7 +32,6 @@ func squares(n int) Seq2[int, int64] {
 }
 
 func TestPull(t *testing.T) {
-
 	for end := 0; end <= 3; end++ {
 		t.Run(fmt.Sprint(end), func(t *testing.T) {
 			ng := runtime.NumGoroutine()