From 124dc10a92356948f0111bc053982d82543d9520 Mon Sep 17 00:00:00 2001
From: Peter Meilstrup <peter.meilstrup@gmail.com>
Date: Mon, 1 Jul 2024 12:41:05 -0700
Subject: [PATCH] backport R_existsVarInFrame

---
 src/vadr.c | 16 ++++++++++++++++
 src/vadr.h | 12 +++++-------
 2 files changed, 21 insertions(+), 7 deletions(-)

diff --git a/src/vadr.c b/src/vadr.c
index 6cc7750..c2b08cd 100644
--- a/src/vadr.c
+++ b/src/vadr.c
@@ -62,3 +62,19 @@ SEXP new_weird_promise(SEXP expr, SEXP env, SEXP value) {
   UNPROTECT(1);
   return out;
 }
+
+#if R_VERSION < R_Version(4, 4, 1)
+SEXP allocLang(int n)
+{
+  if (n > 0)
+    return LCONS(R_NilValue, allocList(n - 1));
+  else
+    return R_NilValue;
+}
+#endif
+
+#if R_VERSION < R_Version(4, 2, 0)
+Rboolean R_existsVarInFrame(SEXP rho, SEXP symbol) {
+  return (Rf_findVarInFrame3(rho, symbol, FALSE) != R_UnboundValue);
+}
+#endif
diff --git a/src/vadr.h b/src/vadr.h
index 979be85..1d12920 100644
--- a/src/vadr.h
+++ b/src/vadr.h
@@ -66,13 +66,7 @@ SEXP peek_promise(SEXP prom);
 #endif
 
 #if R_VERSION < R_Version(4, 4, 1)
-SEXP allocLang(int n)
-{
-  if (n > 0)
-    return LCONS(R_NilValue, allocList(n - 1));
-  else
-    return R_NilValue;
-}
+SEXP allocLang(int n);
 #endif
 
 #if R_VERSION < R_Version(4, 5, 0)
@@ -80,3 +74,7 @@ SEXP allocLang(int n)
 # define R_ClosureEnv(x) CLOENV(x)
 # define R_ParentEnv(x) ENCLOS(x)
 #endif
+
+#if R_VERSION < R_Version(4, 2, 0)
+Rboolean R_existsVarInFrame(SEXP rho, SEXP symbol);
+#endif