fix not being able to dbg variable

crates/compiler/can/src/expr.rs

@@ -1065,12 +1065,20 @@ pub fn canonicalize_expr<'a>(
             output.union(output1);
             output.union(output2);
 
+            // the symbol is used to bind the condition `x = condition`, adn identify this `dbg`.
+            // That would cause issues if we dbg a variable, like `dbg y`, because in the IR we
+            // cannot alias variables. Hence, we make the dbg use that same variable `y`
+            let symbol = match &loc_condition.value {
+                Expr::Var(symbol, _) => *symbol,
+                _ => scope.gen_unique_symbol(),
+            };
+
             (
                 Dbg {
                     loc_condition: Box::new(loc_condition),
                     loc_continuation: Box::new(loc_continuation),
                     variable: var_store.fresh(),
-                    symbol: scope.gen_unique_symbol(),
+                    symbol,
                 },
                 output,
             )

crates/compiler/mono/src/ir.rs

@@ -6570,16 +6570,24 @@ pub fn from_can<'a>(
             let expr = Expr::Call(call);
             let mut stmt = Stmt::Let(dbg_symbol, expr, dbg_layout, env.arena.alloc(rest));
 
-            stmt = with_hole(
-                env,
-                loc_condition.value,
-                variable,
-                procs,
-                layout_cache,
-                dbg_symbol,
-                env.arena.alloc(stmt),
+            let symbol_is_reused = matches!(
+                can_reuse_symbol(env, procs, &loc_condition.value, variable),
+                ReuseSymbol::Value(_)
             );
 
+            // skip evaluating the condition if it's just a symbol
+            if !symbol_is_reused {
+                stmt = with_hole(
+                    env,
+                    loc_condition.value,
+                    variable,
+                    procs,
+                    layout_cache,
+                    dbg_symbol,
+                    env.arena.alloc(stmt),
+                );
+            }
+
             stmt
         }
 

crates/repl_expect/src/run.rs

@@ -499,7 +499,7 @@ fn render_dbg_failure<'a>(
     let data = expectations.get_mut(&module_id).unwrap();
 
     let current = match data.dbgs.get(&dbg_symbol) {
-        None => panic!("region {failure_region:?} not in list of expects"),
+        None => panic!("region {failure_region:?} not in list of dbgs"),
         Some(current) => current,
     };
     let failure_region = current.region;