crypto/x509/internal/macos: rename package to lowercase

Also add a test to lock in this policy.

Fixes #40065

Change-Id: Iedc4586f2f5598046d84132a8f3bba8f2e93ddc2
Reviewed-on: https://go-review.googlesource.com/c/go/+/241274
Run-TryBot: Dmitri Shuralyov <dmitshur@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Ian Lance Taylor <iant@golang.org>

src/crypto/x509/root_darwin_amd64.go

@@ -8,7 +8,7 @@ package x509
 
 import (
 	"bytes"
-	"crypto/x509/internal/macOS"
+	macOS "crypto/x509/internal/macos"
 	"fmt"
 	"os"
 	"strings"

src/go/build/deps_test.go

@@ -10,6 +10,7 @@ package build
 import (
 	"bytes"
 	"fmt"
+	"internal/testenv"
 	"io/ioutil"
 	"os"
 	"path/filepath"
@@ -387,7 +388,7 @@ var depsRules = `
 	< golang.org/x/crypto/poly1305
 	< golang.org/x/crypto/chacha20poly1305
 	< golang.org/x/crypto/hkdf
-	< crypto/x509/internal/macOS
+	< crypto/x509/internal/macos
 	< crypto/x509/pkix
 	< crypto/x509
 	< crypto/tls;
@@ -516,8 +517,7 @@ func listStdPkgs(goroot string) ([]string, error) {
 }
 
 func TestDependencies(t *testing.T) {
-	iOS := runtime.GOOS == "darwin" && runtime.GOARCH == "arm64"
-	if iOS {
+	if !testenv.HasSrc() {
 		// Tests run in a limited file system and we do not
 		// provide access to every source file.
 		t.Skipf("skipping on %s/%s, missing full GOROOT", runtime.GOOS, runtime.GOARCH)
@@ -805,3 +805,23 @@ func (p *depsParser) nextToken() string {
 		}
 	}
 }
+
+// TestStdlibLowercase tests that all standard library package names are
+// lowercase. See Issue 40065.
+func TestStdlibLowercase(t *testing.T) {
+	if !testenv.HasSrc() {
+		t.Skipf("skipping on %s/%s, missing full GOROOT", runtime.GOOS, runtime.GOARCH)
+	}
+
+	ctxt := Default
+	all, err := listStdPkgs(ctxt.GOROOT)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	for _, pkgname := range all {
+		if strings.ToLower(pkgname) != pkgname {
+			t.Errorf("package %q should not use upper-case path", pkgname)
+		}
+	}
+}

src/runtime/sys_darwin.go

@@ -129,7 +129,7 @@ func syscall_rawSyscall6(fn, a1, a2, a3, a4, a5, a6 uintptr) (r1, r2, err uintpt
 
 // syscallNoErr is used in crypto/x509 to call into Security.framework and CF.
 
-//go:linkname crypto_x509_syscall crypto/x509/internal/macOS.syscall
+//go:linkname crypto_x509_syscall crypto/x509/internal/macos.syscall
 //go:nosplit
 //go:cgo_unsafe_args
 func crypto_x509_syscall(fn, a1, a2, a3, a4, a5, a6 uintptr) (r1 uintptr) {