Merge pull request #9918 from 9999years/debugger-locals-for-let-expressions

Expose locals from `let` expressions to the debugger

(cherry picked from commit acef4f17a2daab4ccdf656bdf229792db2f779e4)
Change-Id: Ib3623254f67ac762f4e7230d625e9f87dff38a84

2 files changed, 12 insertions, 6 deletions

diff --git a/doc/manual/rl-next/debugger-locals-for-let-expressions.md b/doc/manual/rl-next/debugger-locals-for-let-expressions.md
new file mode 100644
index 000000000..736208724
--- /dev/null
+++ b/doc/manual/rl-next/debugger-locals-for-let-expressions.md
@@ -0,0 +1,9 @@
+---
+synopsis: "`--debugger` can now access bindings from `let` expressions"
+prs: 9918
+issues: 8827.
+---
+
+Breakpoints and errors in the bindings of a `let` expression can now access
+those bindings in the debugger. Previously, only the body of `let` expressions
+could access those bindings.
diff --git a/src/libexpr/nixexpr.cc b/src/libexpr/nixexpr.cc
index edab297f2..b34112be1 100644
--- a/src/libexpr/nixexpr.cc
+++ b/src/libexpr/nixexpr.cc
@@ -470,9 +470,6 @@ void ExprCall::bindVars(EvalState & es, const std::shared_ptr<const StaticEnv> &
 
 void ExprLet::bindVars(EvalState & es, const std::shared_ptr<const StaticEnv> & env)
 {
-    if (es.debugRepl)
-        es.exprEnvs.insert(std::make_pair(this, env));
-
     auto newEnv = std::make_shared<StaticEnv>(nullptr, env.get(), attrs->attrs.size());
 
     Displacement displ = 0;
@@ -484,6 +481,9 @@ void ExprLet::bindVars(EvalState & es, const std::shared_ptr<const StaticEnv> &
     for (auto & i : attrs->attrs)
         i.second.e->bindVars(es, i.second.inherited ? env : newEnv);
 
+    if (es.debugRepl)
+        es.exprEnvs.insert(std::make_pair(this, newEnv));
+
     body->bindVars(es, newEnv);
 }
 
@@ -508,9 +508,6 @@ void ExprWith::bindVars(EvalState & es, const std::shared_ptr<const StaticEnv> &
             break;
         }
 
-    if (es.debugRepl)
-        es.exprEnvs.insert(std::make_pair(this, env));
-
     attrs->bindVars(es, env);
     auto newEnv = std::make_shared<StaticEnv>(this, env.get());
     body->bindVars(es, newEnv);