1 files changed, 23 insertions, 10 deletions

diff --git a/src/reflect/value.go b/src/reflect/value.go
index a14131e1f8..24eab6a2c6 100644
--- a/src/reflect/value.go
+++ b/src/reflect/value.go
@@ -90,6 +90,7 @@ func (f flag) ro() flag {
 
 // pointer returns the underlying pointer represented by v.
 // v.Kind() must be Ptr, Map, Chan, Func, or UnsafePointer
+// if v.Kind() == Ptr, the base type must not be go:notinheap.
 func (v Value) pointer() unsafe.Pointer {
 	if v.typ.size != ptrSize || !v.typ.pointers() {
 		panic("can't call pointer on a non-pointer Value")
@@ -635,10 +636,11 @@ func methodReceiver(op string, v Value, methodIndex int) (rcvrtype *rtype, t *fu
 	i := methodIndex
 	if v.typ.Kind() == Interface {
 		tt := (*interfaceType)(unsafe.Pointer(v.typ))
-		if uint(i) >= uint(len(tt.methods)) {
+		ttmethods := tt.methods()
+		if uint(i) >= uint(len(ttmethods)) {
 			panic("reflect: internal error: invalid method index")
 		}
-		m := &tt.methods[i]
+		m := &ttmethods[i]
 		if !tt.nameOff(m.name).isExported() {
 			panic("reflect: " + op + " of unexported method")
 		}
@@ -812,7 +814,7 @@ func (v Value) Elem() Value {
 	switch k {
 	case Interface:
 		var eface interface{}
-		if v.typ.NumMethod() == 0 {
+		if isEmptyIface(v.typ) {
 			eface = *(*interface{})(v.ptr)
 		} else {
 			eface = (interface{})(*(*interface {
@@ -1033,7 +1035,7 @@ func valueInterface(v Value, safe bool) interface{} {
 		// Special case: return the element inside the interface.
 		// Empty interface has one layout, all interfaces with
 		// methods have a second layout.
-		if v.NumMethod() == 0 {
+		if isEmptyIface(v.typ) {
 			return *(*interface{})(v.ptr)
 		}
 		return *(*interface {
@@ -1452,7 +1454,16 @@ func (v Value) Pointer() uintptr {
 	// TODO: deprecate
 	k := v.kind()
 	switch k {
-	case Chan, Map, Ptr, UnsafePointer:
+	case Ptr:
+		if v.typ.ptrdata == 0 {
+			// Handle pointers to go:notinheap types directly,
+			// so we never materialize such pointers as an
+			// unsafe.Pointer. (Such pointers are always indirect.)
+			// See issue 42076.
+			return *(*uintptr)(v.ptr)
+		}
+		fallthrough
+	case Chan, Map, UnsafePointer:
 		return uintptr(v.pointer())
 	case Func:
 		if v.flag&flagMethod != 0 {
@@ -1908,10 +1919,11 @@ func (v Value) Type() Type {
 	if v.typ.Kind() == Interface {
 		// Method on interface.
 		tt := (*interfaceType)(unsafe.Pointer(v.typ))
-		if uint(i) >= uint(len(tt.methods)) {
+		ttmethods := tt.methods()
+		if uint(i) >= uint(len(ttmethods)) {
 			panic("reflect: internal error: invalid method index")
 		}
-		m := &tt.methods[i]
+		m := &ttmethods[i]
 		return v.typ.typeOff(m.typ)
 	}
 	// Method on concrete type.
@@ -2429,7 +2441,7 @@ func (v Value) assignTo(context string, dst *rtype, target unsafe.Pointer) Value
 			return Value{dst, nil, flag(Interface)}
 		}
 		x := valueInterface(v, false)
-		if dst.NumMethod() == 0 {
+		if isEmptyIface(dst) {
 			*(*interface{})(target) = x
 		} else {
 			ifaceE2I(dst, x, target)
@@ -2718,10 +2730,11 @@ func cvtDirect(v Value, typ Type) Value {
 func cvtT2I(v Value, typ Type) Value {
 	target := unsafe_New(typ.common())
 	x := valueInterface(v, false)
-	if typ.NumMethod() == 0 {
+	rt := typ.(*rtype)
+	if isEmptyIface(rt) {
 		*(*interface{})(target) = x
 	} else {
-		ifaceE2I(typ.(*rtype), x, target)
+		ifaceE2I(rt, x, target)
 	}
 	return Value{typ.common(), target, v.flag.ro() | flagIndir | flag(Interface)}
 }