Merge #3508

3508: Use a not so dummy implementation of env macro r=edwin0cheng a=edwin0cheng

Currently we have a dummy `env` macro implementation which expand to an empty string, such that a `include!(concat!(env!("OUT_DIR"), "/foo.rs"))` will become `include!("/foo.rs")`, and here may be a infinite loop. :)

This PR use a not so dummy version of `env` macro to prevent this infinite loop. 

Co-authored-by: Edwin Cheng <[email protected]>

1 files changed, 5 insertions, 2 deletions

diff --git a/crates/ra_hir_expand/src/builtin_macro.rs b/crates/ra_hir_expand/src/builtin_macro.rs
index 9fc33e4b1..a57e9285f 100644
--- a/crates/ra_hir_expand/src/builtin_macro.rs
+++ b/crates/ra_hir_expand/src/builtin_macro.rs
@@ -142,7 +142,10 @@ fn env_expand(
     _tt: &tt::Subtree,
 ) -> Result<tt::Subtree, mbe::ExpandError> {
     // dummy implementation for type-checking purposes
-    let expanded = quote! { "" };
+    // we cannot use an empty string here, because for
+    // `include!(concat!(env!("OUT_DIR"), "/foo.rs"))` will become
+    // `include!("foo.rs"), which maybe infinite loop
+    let expanded = quote! { "__RA_UNIMPLEMENTATED__" };
 
     Ok(expanded)
 }
@@ -394,7 +397,7 @@ mod tests {
             "#,
         );
 
-        assert_eq!(expanded, "\"\"");
+        assert_eq!(expanded, "\"__RA_UNIMPLEMENTATED__\"");
     }
 
     #[test]