Implement Chalk's debug methods using TLS

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.

1 files changed, 14 insertions, 12 deletions

diff --git a/crates/ra_hir_ty/src/display.rs b/crates/ra_hir_ty/src/display.rs
index 0e9313aa1..d03bbd5a7 100644
--- a/crates/ra_hir_ty/src/display.rs
+++ b/crates/ra_hir_ty/src/display.rs
@@ -247,19 +247,21 @@ impl HirDisplay for ApplicationTy {
                 }
             }
             TypeCtor::Closure { .. } => {
-                let sig = self.parameters[0]
-                    .callable_sig(f.db)
-                    .expect("first closure parameter should contain signature");
-                if sig.params().is_empty() {
-                    write!(f, "||")?;
-                } else if f.omit_verbose_types() {
-                    write!(f, "|{}|", TYPE_HINT_TRUNCATION)?;
+                let sig = self.parameters[0].callable_sig(f.db);
+                if let Some(sig) = sig {
+                    if sig.params().is_empty() {
+                        write!(f, "||")?;
+                    } else if f.omit_verbose_types() {
+                        write!(f, "|{}|", TYPE_HINT_TRUNCATION)?;
+                    } else {
+                        write!(f, "|")?;
+                        f.write_joined(sig.params(), ", ")?;
+                        write!(f, "|")?;
+                    };
+                    write!(f, " -> {}", sig.ret().display(f.db))?;
                 } else {
-                    write!(f, "|")?;
-                    f.write_joined(sig.params(), ", ")?;
-                    write!(f, "|")?;
-                };
-                write!(f, " -> {}", sig.ret().display(f.db))?;
+                    write!(f, "{{closure}}")?;
+                }
             }
         }
         Ok(())