Switch from fastmap to rlang for weakref functions

DESCRIPTION

@@ -90,7 +90,7 @@ Suggests:
     reactlog (>= 1.0.0),
     magrittr
 Remotes:
-    r-lib/fastmap@weakref
+    wch/rlang@weakref
 URL: http://shiny.rstudio.com
 BugReports: https://github.com/rstudio/shiny/issues
 Collate:

R/reactives.R

@@ -25,7 +25,7 @@ Dependents <- R6Class(
         }
 
         if (ctx$isWeak()) {
-          .dependents$set(ctx$id, fastmap::make_weakref(ctx))
+          .dependents$set(ctx$id, rlang::new_weakref(ctx))
         } else {
           .dependents$set(ctx$id, ctx)
         }
@@ -50,8 +50,8 @@ Dependents <- R6Class(
       lapply(
         .dependents$values(sort = TRUE),
         function(ctx) {
-          if (fastmap::is_weakref(ctx)) {
-            ctx <- fastmap::get_weakref(ctx)
+          if (rlang::is_weakref(ctx)) {
+            ctx <- rlang::wref_key(ctx)
             if (is.null(ctx)) {
               # Can get here if weakref target was GC'd
               return()