Add new import macro prototype.

util/import_macro/BUILD.bazel

@@ -0,0 +1,34 @@
+load("//rust:defs.bzl", "rust_library", "rust_proc_macro", "rust_test")
+
+rust_proc_macro(
+    name = "import",
+    srcs = [
+        "import.rs",
+    ],
+    deps = [
+        ":import_internal",
+        # syn
+    ],
+)
+
+rust_library(
+    name = "import_internal",
+    srcs = [
+        "import_internal.rs",
+    ],
+    deps = [
+        # aho_corasick
+        # lazy_static
+        # proc_macro2
+        # quote
+        # syn
+    ],
+)
+
+rust_test(
+    name = "import_internal_test",
+    crate = ":import_internal",
+    deps = [
+        # quickcheck
+    ],
+)

util/import_macro/import.rs

@@ -0,0 +1,15 @@
+use proc_macro;
+use syn::parse_macro_input;
+
+use import_internal;
+
+// Flipping this bool allows easy switching between renaming crates and not.
+const RENAME_1P_CRATES: bool = true;
+
+#[proc_macro]
+pub fn import(input: proc_macro::TokenStream) -> proc_macro::TokenStream {
+    let input = parse_macro_input!(input as import_internal::ImportMacroInput);
+    import_internal::expand_imports(input, RENAME_1P_CRATES)
+        .unwrap_or_else(|errors| errors.into_iter().map(|e| e.into_compile_error()).collect())
+        .into()
+}