text/template: support range-over-int

Fixes #66107

Change-Id: I19b466e3fb17557cf4f198b7fd8c13e774d854b1
Reviewed-on: https://go-review.googlesource.com/c/go/+/615095
Auto-Submit: Ian Lance Taylor <iant@golang.org>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Reviewed-by: Carlos Amedee <carlos@golang.org>
Commit-Queue: Ian Lance Taylor <iant@golang.org>
Reviewed-by: Ian Lance Taylor <iant@google.com>

doc/next/6-stdlib/99-minor/text/template/66107.md

@@ -1 +1 @@
-Templates now support range-over-func.
+Templates now support range-over-func and range-over-int.

src/text/template/doc.go

@@ -99,7 +99,7 @@ data, defined in detail in the corresponding sections that follow.
 
 	{{range pipeline}} T1 {{end}}
 		The value of the pipeline must be an array, slice, map, iter.Seq,
-		iter.Seq2 or channel.
+		iter.Seq2, integer or channel.
 		If the value of the pipeline has length zero, nothing is output;
 		otherwise, dot is set to the successive elements of the array,
 		slice, or map and T1 is executed. If the value is a map and the
@@ -108,7 +108,7 @@ data, defined in detail in the corresponding sections that follow.
 
 	{{range pipeline}} T1 {{else}} T0 {{end}}
 		The value of the pipeline must be an array, slice, map, iter.Seq,
-		iter.Seq2 or channel.
+		iter.Seq2, integer or channel.
 		If the value of the pipeline has length zero, dot is unaffected and
 		T0 is executed; otherwise, dot is set to the successive elements
 		of the array, slice, or map and T1 is executed.

src/text/template/exec.go

@@ -395,6 +395,22 @@ func (s *state) walkRange(dot reflect.Value, r *parse.RangeNode) {
 		s.walk(elem, r.List)
 	}
 	switch val.Kind() {
+	case reflect.Int, reflect.Int8, reflect.Int16, reflect.Int32, reflect.Int64,
+		reflect.Uint, reflect.Uint8, reflect.Uint16, reflect.Uint32, reflect.Uint64, reflect.Uintptr:
+		if len(r.Pipe.Decl) > 1 {
+			s.errorf("can't use %s to iterate over more than one variable", val)
+			break
+		}
+		run := false
+		for v := range val.Seq() {
+			run = true
+			// Pass element as second value, as we do for channels.
+			oneIteration(reflect.Value{}, v)
+		}
+		if !run {
+			break
+		}
+		return
 	case reflect.Array, reflect.Slice:
 		if val.Len() == 0 {
 			break

src/text/template/exec_test.go

@@ -613,6 +613,19 @@ var execTests = []execTest{
 	{"i,x range iter.Seq[int]", `{{$i := 0}}{{$x := 0}}{{range $i = .}}{{$i}}{{end}}`, "01", fVal1(2), true},
 	{"range iter.Seq[int] else", `{{range $i := .}}{{$i}}{{else}}empty{{end}}`, "empty", fVal1(0), true},
 	{"range iter.Seq2[int,int] else", `{{range $i := .}}{{$i}}{{else}}empty{{end}}`, "empty", fVal2(0), true},
+	{"range int8", rangeTestInt, rangeTestData[int8](), int8(5), true},
+	{"range int16", rangeTestInt, rangeTestData[int16](), int16(5), true},
+	{"range int32", rangeTestInt, rangeTestData[int32](), int32(5), true},
+	{"range int64", rangeTestInt, rangeTestData[int64](), int64(5), true},
+	{"range int", rangeTestInt, rangeTestData[int](), int(5), true},
+	{"range uint8", rangeTestInt, rangeTestData[uint8](), uint8(5), true},
+	{"range uint16", rangeTestInt, rangeTestData[uint16](), uint16(5), true},
+	{"range uint32", rangeTestInt, rangeTestData[uint32](), uint32(5), true},
+	{"range uint64", rangeTestInt, rangeTestData[uint64](), uint64(5), true},
+	{"range uint", rangeTestInt, rangeTestData[uint](), uint(5), true},
+	{"range uintptr", rangeTestInt, rangeTestData[uintptr](), uintptr(5), true},
+	{"range uintptr(0)", `{{range $v := .}}{{print $v}}{{else}}empty{{end}}`, "empty", uintptr(0), true},
+	{"range 5", `{{range $v := 5}}{{printf "%T%d" $v $v}}{{end}}`, rangeTestData[int](), nil, true},
 
 	// Cute examples.
 	{"or as if true", `{{or .SI "slice is empty"}}`, "[3 4 5]", tVal, true},
@@ -737,6 +750,17 @@ func fVal2(i int) iter.Seq2[int, int] {
 	}
 }
 
+const rangeTestInt = `{{range $v := .}}{{printf "%T%d" $v $v}}{{end}}`
+
+func rangeTestData[T int | int8 | int16 | int32 | int64 | uint | uint8 | uint16 | uint32 | uint64 | uintptr]() string {
+	I := T(5)
+	var buf strings.Builder
+	for i := T(0); i < I; i++ {
+		fmt.Fprintf(&buf, "%T%d", i, i)
+	}
+	return buf.String()
+}
+
 func zeroArgs() string {
 	return "zeroArgs"
 }