1 files changed, 80 insertions, 0 deletions
diff --git a/test/fixedbugs/issue4909b.go b/test/fixedbugs/issue4909b.go
new file mode 100644
index 0000000..7d79227
--- /dev/null
+++ b/test/fixedbugs/issue4909b.go
@@ -0,0 +1,80 @@
+// errorcheckoutput
+
+package main
+
+import "fmt"
+
+// We are going to define 256 types T(n),
+// such that T(n) embeds T(2n) and *T(2n+1).
+
+func main() {
+	fmt.Printf("// errorcheck\n\n")
+	fmt.Printf("package p\n\n")
+	fmt.Println(`import "unsafe"`)
+
+	// Dump types.
+	for n := 1; n < 256; n++ {
+		writeStruct(n)
+	}
+	// Dump leaves
+	for n := 256; n < 512; n++ {
+		fmt.Printf("type T%d int\n", n)
+	}
+
+	fmt.Printf("var t T1\n")
+	fmt.Printf("var p *T1\n")
+
+	// Simple selectors
+	for n := 2; n < 256; n++ {
+		writeDot(n)
+	}
+
+	// Double selectors
+	for n := 128; n < 256; n++ {
+		writeDot(n/16, n)
+	}
+
+	// Triple selectors
+	for n := 128; n < 256; n++ {
+		writeDot(n/64, n/8, n)
+	}
+}
+
+const structTpl = `
+type T%d struct {
+	A%d int
+	T%d
+	*T%d
+}
+`
+
+func writeStruct(n int) {
+	fmt.Printf(structTpl, n, n, 2*n, 2*n+1)
+}
+
+func writeDot(ns ...int) {
+	for _, root := range []string{"t", "p"} {
+		fmt.Printf("const _ = unsafe.Offsetof(%s", root)
+		for _, n := range ns {
+			fmt.Printf(".T%d", n)
+		}
+		// Does it involve an indirection?
+		nlast := ns[len(ns)-1]
+		nprev := 1
+		if len(ns) > 1 {
+			nprev = ns[len(ns)-2]
+		}
+		isIndirect := false
+		for n := nlast / 2; n > nprev; n /= 2 {
+			if n%2 == 1 {
+				isIndirect = true
+				break
+			}
+		}
+		fmt.Print(")")
+		if isIndirect {
+			fmt.Print(` // ERROR "indirection|embedded via a pointer"`)
+		}
+		fmt.Print("\n")
+	}
+}