Build test-macros in a build script

crates/proc_macro_test/imp/src/lib.rs

@@ -0,0 +1,48 @@
+//! Exports a few trivial procedural macros for testing.
+
+use proc_macro::TokenStream;
+
+#[proc_macro]
+pub fn fn_like_noop(args: TokenStream) -> TokenStream {
+    args
+}
+
+#[proc_macro]
+pub fn fn_like_panic(args: TokenStream) -> TokenStream {
+    panic!("fn_like_panic!({})", args);
+}
+
+#[proc_macro]
+pub fn fn_like_error(args: TokenStream) -> TokenStream {
+    format!("compile_error!(\"fn_like_error!({})\");", args).parse().unwrap()
+}
+
+#[proc_macro_attribute]
+pub fn attr_noop(_args: TokenStream, item: TokenStream) -> TokenStream {
+    item
+}
+
+#[proc_macro_attribute]
+pub fn attr_panic(args: TokenStream, item: TokenStream) -> TokenStream {
+    panic!("#[attr_panic {}] {}", args, item);
+}
+
+#[proc_macro_attribute]
+pub fn attr_error(args: TokenStream, item: TokenStream) -> TokenStream {
+    format!("compile_error!(\"#[attr_error({})] {}\");", args, item).parse().unwrap()
+}
+
+#[proc_macro_derive(DeriveEmpty)]
+pub fn derive_empty(_item: TokenStream) -> TokenStream {
+    TokenStream::new()
+}
+
+#[proc_macro_derive(DerivePanic)]
+pub fn derive_panic(item: TokenStream) -> TokenStream {
+    panic!("#[derive(DerivePanic)] {}", item);
+}
+
+#[proc_macro_derive(DeriveError)]
+pub fn derive_error(item: TokenStream) -> TokenStream {
+    format!("compile_error!(\"#[derive(DeriveError)] {}\");", item).parse().unwrap()
+}