Support variadic provider and injector functions (#91)

Fixes #61

internal/wire/testdata/Varargs/foo/foo.go

@@ -0,0 +1,31 @@
+// Copyright 2018 The Wire Authors
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package main
+
+import (
+	"fmt"
+	"strings"
+)
+
+func main() {
+	fmt.Println(injectedMessage("", "Hello,", "World!"))
+}
+
+type title string
+
+// provideMessage provides a friendly user greeting.
+func provideMessage(words ...string) string {
+	return strings.Join(words, " ")
+}

internal/wire/testdata/Varargs/foo/wire.go

@@ -0,0 +1,26 @@
+// Copyright 2018 The Wire Authors
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+//+build wireinject
+
+package main
+
+import (
+	"github.com/google/wire"
+)
+
+func injectedMessage(t title, lines ...string) string {
+	wire.Build(provideMessage)
+	return ""
+}

internal/wire/testdata/Varargs/pkg

@@ -0,0 +1 @@
+example.com/foo

internal/wire/testdata/Varargs/want/program_out.txt

@@ -0,0 +1 @@
+Hello, World!

internal/wire/testdata/Varargs/want/wire_gen.go

@@ -0,0 +1,13 @@
+// Code generated by Wire. DO NOT EDIT.
+
+//go:generate wire
+//+build !wireinject
+
+package main
+
+// Injectors from wire.go:
+
+func injectedMessage(t title, lines ...string) string {
+	string2 := provideMessage(lines...)
+	return string2
+}