goose: require pointer for first argument to goose.Bind (google/go-cloud#31)

Fixes google/go-cloud#15

internal/goose/parse.go

@@ -496,21 +496,25 @@ func processBind(fset *token.FileSet, info *types.Info, call *ast.CallExpr) (*If
 		return nil, fmt.Errorf("%v: call to Bind takes exactly two arguments", fset.Position(call.Pos()))
 	}
 	// TODO(light): Verify that arguments are simple expressions.
-	iface := info.TypeOf(call.Args[0])
-	methodSet, ok := iface.Underlying().(*types.Interface)
+	ifaceArgType := info.TypeOf(call.Args[0])
+	ifacePtr, ok := ifaceArgType.(*types.Pointer)
 	if !ok {
-		return nil, fmt.Errorf("%v: first argument to bind must be of interface type; found %s", fset.Position(call.Pos()), types.TypeString(iface, nil))
+		return nil, fmt.Errorf("%v: first argument to bind must be a pointer to an interface type; found %s", fset.Position(call.Pos()), types.TypeString(ifaceArgType, nil))
+	}
+	methodSet, ok := ifacePtr.Elem().Underlying().(*types.Interface)
+	if !ok {
+		return nil, fmt.Errorf("%v: first argument to bind must be a pointer to an interface type; found %s", fset.Position(call.Pos()), types.TypeString(ifaceArgType, nil))
 	}
 	provided := info.TypeOf(call.Args[1])
-	if types.Identical(iface, provided) {
+	if types.Identical(ifacePtr.Elem(), provided) {
 		return nil, fmt.Errorf("%v: cannot bind interface to itself", fset.Position(call.Pos()))
 	}
 	if !types.Implements(provided, methodSet) {
-		return nil, fmt.Errorf("%v: %s does not implement %s", fset.Position(call.Pos()), types.TypeString(provided, nil), types.TypeString(iface, nil))
+		return nil, fmt.Errorf("%v: %s does not implement %s", fset.Position(call.Pos()), types.TypeString(provided, nil), types.TypeString(ifaceArgType, nil))
 	}
 	return &IfaceBinding{
 		Pos:      call.Pos(),
-		Iface:    iface,
+		Iface:    ifacePtr.Elem(),
 		Provided: provided,
 	}, nil
 }

internal/goose/testdata/ImportedInterfaceBinding/bar/bar.go

@@ -17,8 +17,8 @@ package main
 import (
 	"fmt"
 
-	"github.com/google/go-cloud/goose"
 	"foo"
+	"github.com/google/go-cloud/goose"
 )
 
 func main() {
@@ -39,4 +39,4 @@ func provideBar() *Bar {
 
 var Set = goose.NewSet(
 	provideBar,
-	goose.Bind(foo.Fooer(nil), (*Bar)(nil)))
+	goose.Bind((*foo.Fooer)(nil), (*Bar)(nil)))

internal/goose/testdata/InterfaceBinding/foo/foo.go

@@ -42,4 +42,4 @@ func provideBar() *Bar {
 
 var Set = goose.NewSet(
 	provideBar,
-	goose.Bind(Fooer(nil), (*Bar)(nil)))
+	goose.Bind((*Fooer)(nil), (*Bar)(nil)))

internal/goose/testdata/InterfaceBindingReuse/foo/foo_goose.go

@@ -24,5 +24,5 @@ func injectFooBar() FooBar {
 	panic(goose.Build(
 		provideBar,
 		provideFooBar,
-		goose.Bind(Fooer(nil), (*Bar)(nil))))
+		goose.Bind((*Fooer)(nil), (*Bar)(nil))))
 }