internal/wire: fix crash when giving wire.Struct a bad first argument

internal/wire/parse.go

@@ -805,7 +805,7 @@ func processStructProvider(fset *token.FileSet, info *types.Info, call *ast.Call
 	st, ok := structPtr.Elem().Underlying().(*types.Struct)
 	if !ok {
 		return nil, notePosition(fset.Position(call.Pos()),
-			fmt.Errorf(firstArgReqFormat, types.TypeString(st, nil)))
+			fmt.Errorf(firstArgReqFormat, types.TypeString(structPtr, nil)))
 	}
 
 	stExpr := call.Args[0].(*ast.CallExpr)

internal/wire/testdata/StructNotAStruct/foo/foo.go

@@ -0,0 +1,27 @@
+// Copyright 2019 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"
+)
+
+func main() {
+	fmt.Println(inject(A{"Hello"}))
+}
+
+type A struct {
+	B string
+}

internal/wire/testdata/StructNotAStruct/foo/wire.go

@@ -0,0 +1,26 @@
+// Copyright 2019 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 inject(a A) string {
+	wire.Build(wire.Struct(new(*A), "*"))
+	return ""
+}

internal/wire/testdata/StructNotAStruct/pkg

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

internal/wire/testdata/StructNotAStruct/want/wire_errs.txt

@@ -0,0 +1 @@
+example.com/foo/wire.go:x:y: first argument to Struct must be a pointer to a named struct; found **example.com/foo.A