From 5655f9d5933a8920d8dd7cedd2af611a9f2a8d35 Mon Sep 17 00:00:00 2001
From: Jack Christensen <jack@jackchristensen.com>
Date: Sat, 8 Oct 2022 08:10:40 -0500
Subject: [PATCH] Fix scan to pointer to pointer to renamed type

refs https://github.com/jackc/pgx/issues/1326
---
 pgtype/pgtype.go      |  7 ++++++-
 pgtype/pgtype_test.go | 12 ++++++++++++
 2 files changed, 18 insertions(+), 1 deletion(-)

diff --git a/pgtype/pgtype.go b/pgtype/pgtype.go
index ce2336a2..536a5fd8 100644
--- a/pgtype/pgtype.go
+++ b/pgtype/pgtype.go
@@ -659,7 +659,12 @@ func TryFindUnderlyingTypeScanPlan(dst any) (plan WrappedScanPlanNextSetter, nex
 	dstValue := reflect.ValueOf(dst)
 
 	if dstValue.Kind() == reflect.Ptr {
-		elemValue := dstValue.Elem()
+		var elemValue reflect.Value
+		if dstValue.IsNil() {
+			elemValue = reflect.New(dstValue.Type().Elem()).Elem()
+		} else {
+			elemValue = dstValue.Elem()
+		}
 		nextDstType := elemKindToPointerTypes[elemValue.Kind()]
 		if nextDstType == nil && elemValue.Kind() == reflect.Slice {
 			if elemValue.Type().Elem().Kind() == reflect.Uint8 {
diff --git a/pgtype/pgtype_test.go b/pgtype/pgtype_test.go
index 8363b3b8..721872d6 100644
--- a/pgtype/pgtype_test.go
+++ b/pgtype/pgtype_test.go
@@ -317,6 +317,18 @@ func TestMapEncodeBinaryFormatDatabaseValuerThatReturnsString(t *testing.T) {
 	require.Equal(t, []byte{0, 0, 0, 42}, buf)
 }
 
+// https://github.com/jackc/pgx/issues/1326
+func TestMapScanPointerToRenamedType(t *testing.T) {
+	srcBuf := []byte("foo")
+	m := pgtype.NewMap()
+
+	var rs *_string
+	err := m.Scan(pgtype.TextOID, pgx.TextFormatCode, srcBuf, &rs)
+	assert.NoError(t, err)
+	require.NotNil(t, rs)
+	assert.Equal(t, "foo", string(*rs))
+}
+
 func BenchmarkMapScanInt4IntoBinaryDecoder(b *testing.B) {
 	m := pgtype.NewMap()
 	src := []byte{0, 0, 0, 42}