3 files changed, 38 insertions, 0 deletions
diff --git a/src/cmd/compile/internal/noder/stencil.go b/src/cmd/compile/internal/noder/stencil.go
index 23f53bac04..d5fb9f338c 100644
--- a/src/cmd/compile/internal/noder/stencil.go
+++ b/src/cmd/compile/internal/noder/stencil.go
@@ -1097,6 +1097,10 @@ func (subst *subster) node(n ir.Node) ir.Node {
 				// A call with an OFUNCINST will get transformed
 				// in stencil() once we have created & attached the
 				// instantiation to be called.
+				// We must transform the arguments of the call now, though,
+				// so that any needed CONVIFACE nodes are exposed,
+				// so the dictionary format is correct
+				transformEarlyCall(call)
 
 			case ir.OXDOT, ir.ODOTTYPE, ir.ODOTTYPE2:
 			default:
diff --git a/src/cmd/compile/internal/noder/transform.go b/src/cmd/compile/internal/noder/transform.go
index 953036eb42..f7115904fe 100644
--- a/src/cmd/compile/internal/noder/transform.go
+++ b/src/cmd/compile/internal/noder/transform.go
@@ -177,6 +177,12 @@ func transformCall(n *ir.CallExpr) {
 	}
 }
 
+// transformEarlyCall transforms the arguments of a call with an OFUNCINST node.
+func transformEarlyCall(n *ir.CallExpr) {
+	transformArgs(n)
+	typecheckaste(ir.OCALL, n.X, n.IsDDD, n.X.Type().Params(), n.Args)
+}
+
 // transformCompare transforms a compare operation (currently just equals/not
 // equals). Corresponds to the "comparison operators" case in
 // typecheck.typecheck1, including tcArith.
diff --git a/test/typeparam/issue48598.go b/test/typeparam/issue48598.go
new file mode 100644
index 0000000000..ea360f2135
--- /dev/null
+++ b/test/typeparam/issue48598.go
@@ -0,0 +1,28 @@
+// run -gcflags=-G=3
+
+// Copyright 2021 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package main
+
+type Iterator[T any] interface {
+	Iterate()
+}
+
+type IteratorFunc[T any] func(fn func(T) bool)
+
+func (f IteratorFunc[T]) Iterate() {
+}
+
+func FromIterator[T any](it Iterator[T]) {
+	it.Iterate()
+}
+
+func Foo[T, R any]() {
+	FromIterator[R](IteratorFunc[R](nil))
+}
+
+func main() {
+	Foo[int, int]()
+}