Opt in to generate-macro-expansion when building on docs.rs

Author: dtolnay

Cargo.toml

@@ -18,6 +18,7 @@ targets = ["x86_64-unknown-linux-gnu"]
 rustdoc-args = [
     "--cfg=procmacro2_semver_exempt",
     "--generate-link-to-definition",
+    "--generate-macro-expansion",
     "--extern-html-root-url=core=https://doc.rust-lang.org",
     "--extern-html-root-url=alloc=https://doc.rust-lang.org",
     "--extern-html-root-url=std=https://doc.rust-lang.org",