Update

assertion/function/assertiontree/backprop.go

@@ -410,8 +410,34 @@ func backpropAcrossRange(rootNode *RootAssertionNode, lhs []ast.Expr, rhs ast.Ex
 		}
 	}
 
+	// produceNonNil marks the ith lhs expression as nonnil due to limitations of NilAway.
+	produceNonNil := func(i int) {
+		if !util.IsEmptyExpr(lhs[i]) {
+			rootNode.AddProduction(&annotation.ProduceTrigger{
+				Annotation: &annotation.ProduceTriggerNever{},
+				Expr:       lhs[i],
+			})
+		}
+	}
+
 	rhsType := types.Unalias(rootNode.Pass().TypesInfo.Types[rhs].Type)
 
+	// Go 1.23 introduced the `iter` package, which provides a way to iterate over sequences
+	// in a generic way. The `iter.Seq` and `iter.Seq2` types are used to represent sequences
+	// and are used in the `range` statement. We currently do not handle these types yet, so
+	// here we assume that they are deeply non-nil (by adding nonnil producers).
+	// TODO: handle that (#287).
+	if named, ok := rhsType.(*types.Named); ok && named.Obj() != nil && named.Obj().Pkg() != nil && named.Obj().Pkg().Path() == "iter" {
+		if named.Obj().Name() == "Seq" {
+			produceNonNil(0)
+			return nil
+		} else if named.Obj().Name() == "Seq2" {
+			produceNonNil(0)
+			produceNonNil(1)
+			return nil
+		}
+	}
+
 	// This block breaks down the cases for the `range` statement being analyzed,
 	// starting by switching on how many left-hand operands there are
 	switch len(lhs) {

testdata/src/go.uber.org/looprange/looprange.go

@@ -16,6 +16,11 @@
 // <nilaway no inference>
 package looprange
 
+import (
+	"maps"
+	"slices"
+)
+
 func dummyConsume(interface{}) {}
 func dummyBool() bool          { return true }
 
@@ -207,3 +212,14 @@ func testAlias(s MyAlias) {
 		print(myStr)
 	}
 }
+
+func testIter() {
+	i := 42
+	for element := range slices.Values([]*int{&i, &i, nil}) {
+		print(*element) // FN: we do not really handle iterators for now, the elements from iterators are assumed to be nonnil.
+	}
+	for k, v := range maps.All(map[string]*int{"abc": &i, "def": nil}) {
+		print(k)
+		print(*v) // FN: we do not really handle iterators for now, the elements from iterators are assumed to be nonnil.
+	}
+}