1 files changed, 57 insertions, 0 deletions
diff --git a/test/fixedbugs/issue7921.go b/test/fixedbugs/issue7921.go
new file mode 100644
index 0000000..5dce557
--- /dev/null
+++ b/test/fixedbugs/issue7921.go
@@ -0,0 +1,57 @@
+// +build !gcflags_noopt
+// errorcheck -0 -m
+
+// Copyright 2018 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 foo
+
+import "bytes"
+
+// In order to get desired results, we need a combination of
+// both escape analysis and inlining.
+
+func bufferNotEscape() string {
+	// b itself does not escape, only its buf field will be
+	// copied during String() call, but object "handle" itself
+	// can be stack-allocated.
+	var b bytes.Buffer
+	b.WriteString("123")
+	b.Write([]byte{'4'}) // ERROR "\[\]byte{...} does not escape$"
+	return b.String()    // ERROR "inlining call to bytes.\(\*Buffer\).String$" "string\(bytes.b.buf\[bytes.b.off:\]\) escapes to heap$"
+}
+
+func bufferNoEscape2(xs []string) int { // ERROR "xs does not escape$"
+	b := bytes.NewBuffer(make([]byte, 0, 64)) // ERROR "&bytes.Buffer{...} does not escape$" "make\(\[\]byte, 0, 64\) does not escape$" "inlining call to bytes.NewBuffer$"
+	for _, x := range xs {
+		b.WriteString(x)
+	}
+	return b.Len() // ERROR "inlining call to bytes.\(\*Buffer\).Len$"
+}
+
+func bufferNoEscape3(xs []string) string { // ERROR "xs does not escape$"
+	b := bytes.NewBuffer(make([]byte, 0, 64)) // ERROR "&bytes.Buffer{...} does not escape$" "make\(\[\]byte, 0, 64\) does not escape$" "inlining call to bytes.NewBuffer$"
+	for _, x := range xs {
+		b.WriteString(x)
+		b.WriteByte(',')
+	}
+	return b.String() // ERROR "inlining call to bytes.\(\*Buffer\).String$" "string\(bytes.b.buf\[bytes.b.off:\]\) escapes to heap$"
+}
+
+func bufferNoEscape4() []byte {
+	var b bytes.Buffer
+	b.Grow(64) // ERROR "bufferNoEscape4 ignoring self-assignment in bytes.b.buf = bytes.b.buf\[:bytes.m·3\]$" "inlining call to bytes.\(\*Buffer\).Grow$"
+	useBuffer(&b)
+	return b.Bytes() // ERROR "inlining call to bytes.\(\*Buffer\).Bytes$"
+}
+
+func bufferNoEscape5() { // ERROR "can inline bufferNoEscape5$"
+	b := bytes.NewBuffer(make([]byte, 0, 128)) // ERROR "&bytes.Buffer{...} does not escape$" "make\(\[\]byte, 0, 128\) does not escape$" "inlining call to bytes.NewBuffer$"
+	useBuffer(b)
+}
+
+//go:noinline
+func useBuffer(b *bytes.Buffer) { // ERROR "b does not escape$"
+	b.WriteString("1234")
+}