Merge #3748

3748: Implement Chalk's debug methods using TLS r=matklad a=flodiebold

Chalk now panics if we don't implement these methods and run with CHALK_DEBUG, so I thought I'd try to implement them 'properly'. Sadly, it seems impossible to do without transmuting lifetimes somewhere. The problem is that we need a `&dyn HirDatabase` to get names etc., which we can't just put into TLS. I thought I could just use `scoped-tls`, but that doesn't support references to unsized types. So I put the `&dyn` into another struct and put the reference to *that* into the TLS, but I have to transmute the lifetime to 'static for that to work. I think this is sound, but I still don't really want to do it this way...

Having names in the Chalk debug output is very nice, but maybe IDs will have to suffice :disappointed: 

Co-authored-by: Florian Diebold <[email protected]>

1 files changed, 11 insertions, 2 deletions

diff --git a/crates/ra_hir_ty/src/traits.rs b/crates/ra_hir_ty/src/traits.rs
index 5a1e12ce9..21e233379 100644
--- a/crates/ra_hir_ty/src/traits.rs
+++ b/crates/ra_hir_ty/src/traits.rs
@@ -177,7 +177,7 @@ fn solve(
 
     let fuel = std::cell::Cell::new(CHALK_SOLVER_FUEL);
 
-    let solution = solver.solve_limited(&context, goal, || {
+    let should_continue = || {
         context.db.check_canceled();
         let remaining = fuel.get();
         fuel.set(remaining - 1);
@@ -185,12 +185,21 @@ fn solve(
             log::debug!("fuel exhausted");
         }
         remaining > 0
-    });
+    };
+    let mut solve = || solver.solve_limited(&context, goal, should_continue);
+    // don't set the TLS for Chalk unless Chalk debugging is active, to make
+    // extra sure we only use it for debugging
+    let solution =
+        if is_chalk_debug() { chalk::tls::set_current_program(db, solve) } else { solve() };
 
     log::debug!("solve({:?}) => {:?}", goal, solution);
     solution
 }
 
+fn is_chalk_debug() -> bool {
+    std::env::var("CHALK_DEBUG").is_ok()
+}
+
 fn solution_from_chalk(
     db: &dyn HirDatabase,
     solution: chalk_solve::Solution<Interner>,