Merge #6820

6820: Pass the crate environment to proc macros r=jonas-schievink a=jonas-schievink

In theory, fixes https://github.com/rust-analyzer/rust-analyzer/issues/6696.

This seems to result in these obscure crashes for some reason:

```
thread '<unnamed>' panicked at 'called `Option::unwrap()` on a `None` value', /home/jonas/.rustup/toolchains/stable-x86_64-unknown-linux-gnu/lib/rustlib/src/rust/library/proc_macro/src/bridge/scoped_cell.rs:75:51
stack backtrace:
   0: rust_begin_unwind
             at /rustc/7eac88abb2e57e752f3302f02be5f3ce3d7adfb4/library/std/src/panicking.rs:483
   1: core::panicking::panic_fmt
             at /rustc/7eac88abb2e57e752f3302f02be5f3ce3d7adfb4/library/core/src/panicking.rs:85
   2: core::panicking::panic
             at /rustc/7eac88abb2e57e752f3302f02be5f3ce3d7adfb4/library/core/src/panicking.rs:50
   3: core::option::Option<T>::unwrap
             at /home/jonas/.rustup/toolchains/stable-x86_64-unknown-linux-gnu/lib/rustlib/src/rust/library/core/src/option.rs:383
   4: proc_macro::bridge::scoped_cell::ScopedCell<T>::replace
             at /home/jonas/.rustup/toolchains/stable-x86_64-unknown-linux-gnu/lib/rustlib/src/rust/library/proc_macro/src/bridge/scoped_cell.rs:75
   5: proc_macro::bridge::client::BridgeState::with::{{closure}}
             at /home/jonas/.rustup/toolchains/stable-x86_64-unknown-linux-gnu/lib/rustlib/src/rust/library/proc_macro/src/bridge/client.rs:291
   6: std::thread::local::LocalKey<T>::try_with
             at /home/jonas/.rustup/toolchains/stable-x86_64-unknown-linux-gnu/lib/rustlib/src/rust/library/std/src/thread/local.rs:272
   7: std::thread::local::LocalKey<T>::with
             at /home/jonas/.rustup/toolchains/stable-x86_64-unknown-linux-gnu/lib/rustlib/src/rust/library/std/src/thread/local.rs:248
   8: proc_macro::bridge::client::BridgeState::with
             at /home/jonas/.rustup/toolchains/stable-x86_64-unknown-linux-gnu/lib/rustlib/src/rust/library/proc_macro/src/bridge/client.rs:290
   9: proc_macro::bridge::client::<impl proc_macro::bridge::Bridge>::with
             at /home/jonas/.rustup/toolchains/stable-x86_64-unknown-linux-gnu/lib/rustlib/src/rust/library/proc_macro/src/bridge/client.rs:329
  10: proc_macro::bridge::client::run_client::{{closure}}::{{closure}}
             at /home/jonas/.rustup/toolchains/stable-x86_64-unknown-linux-gnu/lib/rustlib/src/rust/library/proc_macro/src/bridge/client.rs:375
  11: proc_macro::bridge::scoped_cell::ScopedCell<T>::set::{{closure}}
             at /home/jonas/.rustup/toolchains/stable-x86_64-unknown-linux-gnu/lib/rustlib/src/rust/library/proc_macro/src/bridge/scoped_cell.rs:80
  12: proc_macro::bridge::scoped_cell::ScopedCell<T>::replace
             at /home/jonas/.rustup/toolchains/stable-x86_64-unknown-linux-gnu/lib/rustlib/src/rust/library/proc_macro/src/bridge/scoped_cell.rs:75
  13: proc_macro::bridge::scoped_cell::ScopedCell<T>::set
             at /home/jonas/.rustup/toolchains/stable-x86_64-unknown-linux-gnu/lib/rustlib/src/rust/library/proc_macro/src/bridge/scoped_cell.rs:80
  14: proc_macro::bridge::client::<impl proc_macro::bridge::Bridge>::enter::{{closure}}
             at /home/jonas/.rustup/toolchains/stable-x86_64-unknown-linux-gnu/lib/rustlib/src/rust/library/proc_macro/src/bridge/client.rs:325
  15: std::thread::local::LocalKey<T>::try_with
             at /home/jonas/.rustup/toolchains/stable-x86_64-unknown-linux-gnu/lib/rustlib/src/rust/library/std/src/thread/local.rs:272
  16: std::thread::local::LocalKey<T>::with
             at /home/jonas/.rustup/toolchains/stable-x86_64-unknown-linux-gnu/lib/rustlib/src/rust/library/std/src/thread/local.rs:248
  17: proc_macro::bridge::client::<impl proc_macro::bridge::Bridge>::enter
             at /home/jonas/.rustup/toolchains/stable-x86_64-unknown-linux-gnu/lib/rustlib/src/rust/library/proc_macro/src/bridge/client.rs:325
  18: proc_macro::bridge::client::run_client::{{closure}}
             at /home/jonas/.rustup/toolchains/stable-x86_64-unknown-linux-gnu/lib/rustlib/src/rust/library/proc_macro/src/bridge/client.rs:370
  19: <std::panic::AssertUnwindSafe<F> as core::ops::function::FnOnce<()>>::call_once
             at /home/jonas/.rustup/toolchains/stable-x86_64-unknown-linux-gnu/lib/rustlib/src/rust/library/std/src/panic.rs:308
  20: std::panicking::try::do_call
             at /home/jonas/.rustup/toolchains/stable-x86_64-unknown-linux-gnu/lib/rustlib/src/rust/library/std/src/panicking.rs:381
  21: __rust_try
  22: std::panicking::try
             at /home/jonas/.rustup/toolchains/stable-x86_64-unknown-linux-gnu/lib/rustlib/src/rust/library/std/src/panicking.rs:345
  23: std::panic::catch_unwind
             at /home/jonas/.rustup/toolchains/stable-x86_64-unknown-linux-gnu/lib/rustlib/src/rust/library/std/src/panic.rs:382
  24: proc_macro::bridge::client::run_client
             at /home/jonas/.rustup/toolchains/stable-x86_64-unknown-linux-gnu/lib/rustlib/src/rust/library/proc_macro/src/bridge/client.rs:369
  25: proc_macro::bridge::client::Client<fn(proc_macro::TokenStream) .> proc_macro::TokenStream>::expand1::run
             at /home/jonas/.rustup/toolchains/stable-x86_64-unknown-linux-gnu/lib/rustlib/src/rust/library/proc_macro/src/bridge/client.rs:410
  26: proc_macro_srv::proc_macro::bridge::server::run_server
  27: proc_macro_srv::dylib::Expander::expand
  28: proc_macro_srv::ProcMacroSrv::expand
  29: proc_macro_srv::cli::run
  30: rust_analyzer::main
```

Co-authored-by: Jonas Schievink <[email protected]>

2 files changed, 7 insertions, 4 deletions

diff --git a/crates/hir_expand/src/db.rs b/crates/hir_expand/src/db.rs
index 077de3727..06f0a3ed9 100644
--- a/crates/hir_expand/src/db.rs
+++ b/crates/hir_expand/src/db.rs
@@ -271,7 +271,7 @@ fn expand_proc_macro(
         _ => unreachable!(),
     };
 
-    expander.expand(db, lazy_id, &macro_arg.0)
+    expander.expand(db, loc.krate, &macro_arg.0)
 }
 
 fn parse_or_expand(db: &dyn AstDatabase, file_id: HirFileId) -> Option<SyntaxNode> {
diff --git a/crates/hir_expand/src/proc_macro.rs b/crates/hir_expand/src/proc_macro.rs
index 38882d2b6..7c77f6ce0 100644
--- a/crates/hir_expand/src/proc_macro.rs
+++ b/crates/hir_expand/src/proc_macro.rs
@@ -1,6 +1,6 @@
 //! Proc Macro Expander stub
 
-use crate::{db::AstDatabase, LazyMacroId};
+use crate::db::AstDatabase;
 use base_db::{CrateId, ProcMacroId};
 use tt::buffer::{Cursor, TokenBuffer};
 
@@ -32,7 +32,7 @@ impl ProcMacroExpander {
     pub fn expand(
         self,
         db: &dyn AstDatabase,
-        _id: LazyMacroId,
+        calling_crate: CrateId,
         tt: &tt::Subtree,
     ) -> Result<tt::Subtree, mbe::ExpandError> {
         match self.proc_macro_id {
@@ -47,7 +47,10 @@ impl ProcMacroExpander {
                 let tt = remove_derive_attrs(tt)
                     .ok_or_else(|| err!("Fail to remove derive for custom derive"))?;
 
-                proc_macro.expander.expand(&tt, None).map_err(mbe::ExpandError::from)
+                // Proc macros have access to the environment variables of the invoking crate.
+                let env = &krate_graph[calling_crate].env;
+
+                proc_macro.expander.expand(&tt, None, &env).map_err(mbe::ExpandError::from)
             }
             None => Err(mbe::ExpandError::UnresolvedProcMacro),
         }