Add source collision test, rust_bindgen doc.

Bug: 159064919
Test: Soong tests pass (and fail if error is modified).
Change-Id: Id4f76e53e11e46ae495f9613a2699c598e7daea4
diff --git a/rust/builder_test.go b/rust/builder_test.go
new file mode 100644
index 0000000..04b67d9
--- /dev/null
+++ b/rust/builder_test.go
@@ -0,0 +1,40 @@
+// Copyright 2020 The Android Open Source Project
+//
+// 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
+//
+//     http://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 rust
+
+import "testing"
+
+func TestSourceProviderCollision(t *testing.T) {
+	testRustError(t, "multiple source providers generate the same filename output: bindings.rs", `
+		rust_binary {
+			name: "source_collider",
+			srcs: [
+				"foo.rs",
+				":libbindings1",
+				":libbindings2",
+			],
+		}
+		rust_bindgen {
+			name: "libbindings1",
+			stem: "bindings",
+			wrapper_src: "src/any.h",
+		}
+		rust_bindgen {
+			name: "libbindings2",
+			stem: "bindings",
+			wrapper_src: "src/any.h",
+		}
+	`)
+}