first whack at passing evalState as an arg to debuggerHook.

src/libcmd/command.cc

@@ -119,13 +119,14 @@ ref<EvalState> EvalCommand::getEvalState()
             #endif
             ;
         if (startReplOnEvalErrors)
-            debuggerHook = [evalState{ref<EvalState>(evalState)}](const Error * error, const Env & env, const Expr & expr) {
+            // debuggerHook = [evalState{ref<EvalState>(evalState)}](const Error * error, const Env & env, const Expr & expr) {
+            debuggerHook = [](const EvalState & evalState, const Error * error, const Env & env, const Expr & expr) {
                 auto dts =
                     error && expr.getPos()
                     ? std::make_unique<DebugTraceStacker>(
-                        *evalState,
+                        evalState,
                         DebugTrace {
-                            .pos = error->info().errPos ? *error->info().errPos : evalState->positions[expr.getPos()],
+                            .pos = error->info().errPos ? *error->info().errPos : evalState.positions[expr.getPos()],
                             .expr = expr,
                             .env = env,
                             .hint = error->info().msg,
@@ -137,8 +138,8 @@ ref<EvalState> EvalCommand::getEvalState()
                     printError("%s\n\n" ANSI_BOLD "Starting REPL to allow you to inspect the current state of the evaluator.\n" ANSI_NORMAL, error->what());
 
                 if (expr.staticEnv) {
-                    auto vm = mapStaticEnvBindings(evalState->symbols, *expr.staticEnv.get(), env);
-                    runRepl(evalState, *vm);
+                    auto vm = mapStaticEnvBindings(evalState.symbols, *expr.staticEnv.get(), env);
+                    runRepl(*const_cast<EvalState*>(&evalState), *vm);
                 }
             };
     }

src/libcmd/command.hh

@@ -274,7 +274,7 @@ void printClosureDiff(
 
 
 void runRepl(
-    ref<EvalState> evalState,
+    EvalState & evalState,
     const ValMap & extraEnv);
 
 }

src/libcmd/repl.cc

@@ -1011,7 +1011,7 @@ std::ostream & NixRepl::printValue(std::ostream & str, Value & v, unsigned int m
 }
 
 void runRepl(
-    ref<EvalState> evalState,
+    EvalState& evalState,
     const ValMap & extraEnv)
 {
     auto repl = std::make_unique<NixRepl>(evalState);

src/libexpr/eval.cc

@@ -1044,7 +1044,7 @@ DebugTraceStacker::DebugTraceStacker(EvalState & evalState, DebugTrace t)
 {
     evalState.debugTraces.push_front(trace);
     if (evalState.debugStop && debuggerHook)
-        debuggerHook(nullptr, trace.env, trace.expr);
+        debuggerHook(evalState, nullptr, trace.env, trace.expr);
 }
 
 void Value::mkString(std::string_view s)

src/libexpr/eval.hh

@@ -136,7 +136,7 @@ public:
     void debugThrow(const E &error, const Env & env, const Expr & expr) const
     {
         if (debuggerHook)
-            debuggerHook(&error, env, expr);
+            debuggerHook(*this, &error, env, expr);
 
         throw error;
     }
@@ -150,7 +150,7 @@ public:
         // DebugTrace stack.
         if (debuggerHook && !debugTraces.empty()) {
             const DebugTrace & last = debugTraces.front();
-            debuggerHook(&e, last.env, last.expr);
+            debuggerHook(*this, &e, last.env, last.expr);
         }
 
         throw e;

src/libexpr/nixexpr.cc

@@ -10,7 +10,7 @@ namespace nix {
 
 /* Launch the nix debugger */
 
-std::function<void(const Error * error, const Env & env, const Expr & expr)> debuggerHook;
+std::function<void(const EvalState & evalState,const Error * error, const Env & env, const Expr & expr)> debuggerHook;
 
 /* Displaying abstract syntax trees. */
 

src/libexpr/nixexpr.hh

@@ -22,7 +22,7 @@ MakeError(UndefinedVarError, Error);
 MakeError(MissingArgumentError, EvalError);
 MakeError(RestrictedPathError, Error);
 
-extern std::function<void(const Error * error, const Env & env, const Expr & expr)> debuggerHook;
+extern std::function<void(const EvalState & evalState, const Error * error, const Env & env, const Expr & expr)> debuggerHook;
 
 /* Position objects. */
 

src/libexpr/primops.cc

@@ -765,7 +765,7 @@ static RegisterPrimOp primop_break({
             });
 
             auto & dt = state.debugTraces.front();
-            debuggerHook(&error, dt.env, dt.expr);
+            debuggerHook(state, &error, dt.env, dt.expr);
 
             if (state.debugQuit) {
                 // If the user elects to quit the repl, throw an exception.

src/libutil/ref.hh

@@ -7,7 +7,7 @@
 namespace nix {
 
 /* A simple non-nullable reference-counted pointer. Actually a wrapper
-   around std::shared_ptr that prevents non-null constructions. */
+   around std::shared_ptr that prevents null constructions. */
 template<typename T>
 class ref
 {