From: Dan Kortschak <dan@kortschak.io>
Date: Sun, 1 Jul 2018 00:03:55 +0000 (+0930)
Subject: cmd/vet,sync: check lock values more precisely
X-Git-Tag: go1.11beta2~104
X-Git-Url: http://www.git.cypherpunks.su/?a=commitdiff_plain;h=c2eba53e7f80df21d51285879d51ab81bcfbf6bc;p=gostls13.git

cmd/vet,sync: check lock values more precisely

Fixes #26165

Change-Id: I1f3bd193af9b6f8461c736330952b6e50d3e00d9
Reviewed-on: https://go-review.googlesource.com/121876
Reviewed-by: Alan Donovan <adonovan@google.com>
Run-TryBot: Rob Pike <r@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
---

diff --git a/src/cmd/vet/copylock.go b/src/cmd/vet/copylock.go
index ce14e1af34..ed88ca8960 100644
--- a/src/cmd/vet/copylock.go
+++ b/src/cmd/vet/copylock.go
@@ -234,13 +234,11 @@ func lockPath(tpkg *types.Package, typ types.Type) typePath {
 		return nil
 	}
 
-	// We're looking for cases in which a reference to this type
-	// can be locked, but a value cannot. This differentiates
+	// We're looking for cases in which a pointer to this type
+	// is a sync.Locker, but a value is not. This differentiates
 	// embedded interfaces from embedded values.
-	if plock := types.NewMethodSet(types.NewPointer(typ)).Lookup(tpkg, "Lock"); plock != nil {
-		if lock := types.NewMethodSet(typ).Lookup(tpkg, "Lock"); lock == nil {
-			return []types.Type{typ}
-		}
+	if types.Implements(types.NewPointer(typ), lockerType) && !types.Implements(typ, lockerType) {
+		return []types.Type{typ}
 	}
 
 	nfields := styp.NumFields()
@@ -254,3 +252,15 @@ func lockPath(tpkg *types.Package, typ types.Type) typePath {
 
 	return nil
 }
+
+var lockerType *types.Interface
+
+// Construct a sync.Locker interface type.
+func init() {
+	nullary := types.NewSignature(nil, nil, nil, false) // func()
+	methods := []*types.Func{
+		types.NewFunc(token.NoPos, nil, "Lock", nullary),
+		types.NewFunc(token.NoPos, nil, "Unlock", nullary),
+	}
+	lockerType = types.NewInterface(methods, nil).Complete()
+}
diff --git a/src/sync/cond.go b/src/sync/cond.go
index 3dcbf1c351..b254c9360a 100644
--- a/src/sync/cond.go
+++ b/src/sync/cond.go
@@ -94,4 +94,5 @@ func (c *copyChecker) check() {
 type noCopy struct{}
 
 // Lock is a no-op used by -copylocks checker from `go vet`.
-func (*noCopy) Lock() {}
+func (*noCopy) Lock()   {}
+func (*noCopy) Unlock() {}