Use minimal defer() instead of local_bindings() (#1093)

Fixes #1089

DESCRIPTION

@@ -15,11 +15,11 @@ BugReports: https://github.com/tidyverse/purrr/issues
 Depends: 
     R (>= 3.5.0)
 Imports:
-    cli (>= 3.4.0),
+    cli (>= 3.6.1),
     lifecycle (>= 1.0.3),
     magrittr (>= 1.5.0),
-    rlang (>= 0.4.10),
-    vctrs (>= 0.5.0)
+    rlang (>= 1.1.1),
+    vctrs (>= 0.6.3)
 Suggests: 
     covr,
     dplyr (>= 0.7.8),

NEWS.md

@@ -1,5 +1,8 @@
 # purrr (development version)
 
+* Deprecation infrastructure in `map_chr()` now has much less overhead 
+  leading to improved performance (#1089).
+
 * purrr now requires R 3.5.0.
 
 # purrr 1.0.1

R/coerce.R

@@ -23,10 +23,18 @@ deprecate_to_char <- function(type) {
   )
 }
 
+
+# Can rewrite after https://github.com/r-lib/rlang/issues/1643
 local_deprecation_user_env <- function(user_env = caller_env(2), frame = caller_env()) {
-  local_bindings(
-    deprecation_user_env = user_env,
-    .env = the,
-    .frame = frame
-  )
+
+  old <- the$deprecation_user_env
+  the$deprecation_user_env <- user_env
+  defer(the$deprecation_user_env <- old, frame)
 }
+
+# Lightweight equivalent of withr::defer()
+defer <- function(expr, env = caller_env(), after = FALSE) {
+  thunk <- as.call(list(function() expr))
+  do.call(on.exit, list(thunk, TRUE, after), envir = env)
+}
+