misc/cgo/test: fix freebsd test failure by moving test to its own package.

(The assertion depends on a per-package gensym counter whose
value varies based on what else is in the package.)

LGTM=khr
R=khr, rsc
CC=golang-codereviews
https://golang.org/cl/169930043

misc/cgo/test/issue9026.go

@@ -1,33 +1,9 @@
 package cgotest
 
-/*
-typedef struct {} git_merge_file_input;
-
-typedef struct {} git_merge_file_options;
-
-void git_merge_file(
-        git_merge_file_input *in,
-        git_merge_file_options *opts) {}
-*/
-import "C"
 import (
-	"fmt"
 	"testing"
+
+	"./issue9026"
 )
 
-func test9026(t *testing.T) {
-	var in C.git_merge_file_input
-	var opts *C.git_merge_file_options
-	C.git_merge_file(&in, opts)
-
-	// Test that the generated type names are deterministic.
-	// (Previously this would fail about 10% of the time.)
-	//
-	// Brittle: the assertion may fail spuriously when the algorithm
-	// changes, but should remain stable otherwise.
-	got := fmt.Sprintf("%T %T", in, opts)
-	want := "cgotest._Ctype_struct___12 *cgotest._Ctype_struct___13"
-	if got != want {
-		t.Errorf("Non-deterministic type names: got %s, want %s", got, want)
-	}
-}
+func test9026(t *testing.T) { issue9026.Test(t) }

misc/cgo/test/issue9026/issue9026.go

@@ -0,0 +1,36 @@
+package issue9026
+
+// This file appears in its own package since the assertion tests the
+// per-package counter used to create fresh identifiers.
+
+/*
+typedef struct {} git_merge_file_input;
+
+typedef struct {} git_merge_file_options;
+
+void git_merge_file(
+        git_merge_file_input *in,
+        git_merge_file_options *opts) {}
+*/
+import "C"
+import (
+	"fmt"
+	"testing"
+)
+
+func Test(t *testing.T) {
+	var in C.git_merge_file_input
+	var opts *C.git_merge_file_options
+	C.git_merge_file(&in, opts)
+
+	// Test that the generated type names are deterministic.
+	// (Previously this would fail about 10% of the time.)
+	//
+	// Brittle: the assertion may fail spuriously when the algorithm
+	// changes, but should remain stable otherwise.
+	got := fmt.Sprintf("%T %T", in, opts)
+	want := "issue9026._Ctype_struct___0 *issue9026._Ctype_struct___1"
+	if got != want {
+		t.Errorf("Non-deterministic type names: got %s, want %s", got, want)
+	}
+}