From fa3649f71fdbcee9cbc3fc4b8b820803c92b607e Mon Sep 17 00:00:00 2001
From: Robert Griesemer <gri@golang.org>
Date: Fri, 6 Feb 2015 12:39:19 -0800
Subject: [PATCH] go/types: don't permit implicit assignments to unexported
 struct fields via literals

Change-Id: I74eec172ba5a319f91c95e33b047f489dfce0c95
Reviewed-on: https://go-review.googlesource.com/4090
Reviewed-by: Alan Donovan <adonovan@google.com>
---
 go/types/expr.go            |  7 ++++++-
 go/types/testdata/expr3.src | 18 ++++++++++++++----
 2 files changed, 20 insertions(+), 5 deletions(-)

diff --git a/go/types/expr.go b/go/types/expr.go
index 71b1b34e..67b91dad 100644
--- a/go/types/expr.go
+++ b/go/types/expr.go
@@ -1057,7 +1057,12 @@ func (check *Checker) exprInternal(x *operand, e ast.Expr, hint Type) exprKind {
 						break // cannot continue
 					}
 					// i < len(fields)
-					etyp := fields[i].typ
+					fld := fields[i]
+					if !fld.Exported() && fld.pkg != check.pkg {
+						check.errorf(x.pos(), "implicit assignment to unexported field %s in %s literal", fld.name, typ)
+						continue
+					}
+					etyp := fld.typ
 					if !check.assignment(x, etyp) {
 						if x.mode != invalid {
 							check.errorf(x.pos(), "cannot use %s as %s value in struct literal", x, etyp)
diff --git a/go/types/testdata/expr3.src b/go/types/testdata/expr3.src
index c370ce34..125a8503 100644
--- a/go/types/testdata/expr3.src
+++ b/go/types/testdata/expr3.src
@@ -4,6 +4,8 @@
 
 package expr3
 
+import "time"
+
 func indexes() {
 	_ = 1 /* ERROR "cannot index" */ [0]
 	_ = indexes /* ERROR "cannot index" */ [0]
@@ -26,7 +28,7 @@ func indexes() {
 	a0 = a[0]
 	_ = a0
 	var a1 int32
-	a1 = a /* ERROR "cannot assign" */ [1] 
+	a1 = a /* ERROR "cannot assign" */ [1]
 	_ = a1
 
 	_ = a[9]
@@ -101,7 +103,6 @@ func indexes() {
 	_, ok = m["bar"]
 	_ = ok
 
-
 	var t string
 	_ = t[- /* ERROR "negative" */ 1]
 	_ = t[- /* ERROR "negative" */ 1 :]
@@ -201,6 +202,15 @@ func struct_literals() {
 		x int
 	}
 	_ = P /* ERROR "invalid composite literal type" */ {}
+
+	// unexported fields
+	_ = time.Time{}
+	_ = time.Time{sec /* ERROR "unknown field" */ : 0}
+	_ = time.Time{
+		0 /* ERROR implicit assignment to unexported field sec in time.Time literal */,
+		0 /* ERROR implicit assignment */ ,
+		nil /* ERROR implicit assignment */ ,
+	}
 }
 
 func array_literals() {
@@ -237,7 +247,7 @@ func array_literals() {
 
 	a0 := [...]int{}
 	assert(len(a0) == 0)
-	
+
 	a1 := [...]int{0, 1, 2}
 	assert(len(a1) == 3)
 	var a13 [3]int
@@ -245,7 +255,7 @@ func array_literals() {
 	a13 = a1
 	a14 = a1 /* ERROR "cannot assign" */
 	_, _ = a13, a14
-	
+
 	a2 := [...]int{- /* ERROR "negative" */ 1: 0}
 	_ = a2