diff --git a/DESCRIPTION b/DESCRIPTION
index b4cd9ec950..ff587e4b88 100644
--- a/DESCRIPTION
+++ b/DESCRIPTION
@@ -276,7 +276,6 @@ Collate:
     'utilities-break.R'
     'utilities-grid.R'
     'utilities-help.R'
-    'utilities-matrix.R'
     'utilities-patterns.R'
     'utilities-resolution.R'
     'utilities-tidy-eval.R'
diff --git a/NAMESPACE b/NAMESPACE
index f0ccf3bec1..7d15e2137a 100644
--- a/NAMESPACE
+++ b/NAMESPACE
@@ -84,8 +84,6 @@ S3method(guide_train,default)
 S3method(guide_transform,default)
 S3method(heightDetails,titleGrob)
 S3method(heightDetails,zeroGrob)
-S3method(interleave,default)
-S3method(interleave,unit)
 S3method(limits,Date)
 S3method(limits,POSIXct)
 S3method(limits,POSIXlt)
@@ -126,8 +124,6 @@ S3method(scale_type,logical)
 S3method(scale_type,numeric)
 S3method(scale_type,ordered)
 S3method(scale_type,sfc)
-S3method(single_value,default)
-S3method(single_value,factor)
 S3method(summary,ggplot)
 S3method(vec_cast,character.mapped_discrete)
 S3method(vec_cast,double.mapped_discrete)
@@ -463,9 +459,20 @@ export(guide_transform)
 export(guides)
 export(has_flipped_aes)
 export(is.Coord)
+export(is.coord)
+export(is.element)
 export(is.facet)
+export(is.geom)
 export(is.ggplot)
 export(is.ggproto)
+export(is.guide)
+export(is.guides)
+export(is.layer)
+export(is.mapping)
+export(is.margin)
+export(is.position)
+export(is.scale)
+export(is.stat)
 export(is.theme)
 export(label_both)
 export(label_bquote)
diff --git a/R/aes-evaluation.R b/R/aes-evaluation.R
index 5554b54772..8e47ebcd1e 100644
--- a/R/aes-evaluation.R
+++ b/R/aes-evaluation.R
@@ -219,12 +219,10 @@ stage_scaled <- function(start = NULL, after_stat = NULL, after_scale = NULL) {
 }
 
 # Regex to determine if an identifier refers to a calculated aesthetic
+# The pattern includes ye olde '...var...' syntax, which was
+# deprecated in 3.4.0 in favour of `after_stat()`
 match_calculated_aes <- "^\\.\\.([a-zA-Z._]+)\\.\\.$"
 
-is_dotted_var <- function(x) {
-  grepl(match_calculated_aes, x)
-}
-
 # Determine if aesthetic is calculated
 is_calculated_aes <- function(aesthetics, warn = FALSE) {
   vapply(aesthetics, is_calculated, warn = warn, logical(1), USE.NAMES = FALSE)
@@ -246,7 +244,8 @@ is_calculated <- function(x, warn = FALSE) {
   if (is.null(x) || is.atomic(x)) {
     FALSE
   } else if (is.symbol(x)) {
-    res <- is_dotted_var(as.character(x))
+    # Test if x is a dotted variable
+    res <- grepl(match_calculated_aes, as.character(x))
     if (res && warn) {
       what <- I(paste0("The dot-dot notation (`", x, "`)"))
       var <- gsub(match_calculated_aes, "\\1", as.character(x))
diff --git a/R/aes.R b/R/aes.R
index 4120657222..d739289b0e 100644
--- a/R/aes.R
+++ b/R/aes.R
@@ -102,6 +102,10 @@ aes <- function(x, y, ...) {
   rename_aes(aes)
 }
 
+#' @export
+#' @rdname is_tests
+is.mapping <- function(x) inherits(x, "uneval")
+
 # Wrap symbolic objects in quosures but pull out constants out of
 # quosures for backward-compatibility
 new_aesthetic <- function(x, env = globalenv()) {
@@ -177,7 +181,12 @@ standardise_aes_names <- function(x) {
   x <- sub("color", "colour", x, fixed = TRUE)
 
   # convert old-style aesthetics names to ggplot version
-  revalue(x, ggplot_global$base_to_ggplot)
+  convert <- ggplot_global$base_to_ggplot
+  convert <- convert[names(convert) %in% x]
+  if (length(convert) > 0) {
+    x[match(names(convert), x)] <- convert
+  }
+  x
 }
 
 # x is a list of aesthetic mappings, as generated by aes()
@@ -448,7 +457,9 @@ arg_enquos <- function(name, frame = caller_env()) {
   quo <- inject(enquo0(!!sym(name)), frame)
   expr <- quo_get_expr(quo)
 
-  if (!is_missing(expr) && is_triple_bang(expr)) {
+  is_triple_bang <- !is_missing(expr) &&
+    is_bang(expr) && is_bang(expr[[2]]) && is_bang(expr[[c(2, 2)]])
+  if (is_triple_bang) {
     # Evaluate `!!!` operand and create a list of quosures
     env <- quo_get_env(quo)
     xs <- eval_bare(expr[[2]][[2]][[2]], env)
diff --git a/R/compat-plyr.R b/R/compat-plyr.R
index efc2865a0c..bb3ea73cb9 100644
--- a/R/compat-plyr.R
+++ b/R/compat-plyr.R
@@ -166,84 +166,7 @@ join_keys <- function(x, y, by) {
   list(x = keys[seq_len(n_x)], y = keys[n_x + seq_len(n_y)],
        n = attr(keys, "n"))
 }
-#' Replace specified values with new values, in a factor or character vector
-#'
-#' An easy to use substitution of elements in a string-like vector (character or
-#' factor). If `x` is a character vector the matching elements will be replaced
-#' directly and if `x` is a factor the matching levels will be replaced
-#'
-#' @param x A character or factor vector
-#' @param replace A named character vector with the names corresponding to the
-#' elements to replace and the values giving the replacement.
-#'
-#' @return A vector of the same class as `x` with the given values replaced
-#'
-#' @keywords internal
-#' @noRd
-#'
-revalue <- function(x, replace) {
-  if (is.character(x)) {
-    replace <- replace[names(replace) %in% x]
-    if (length(replace) == 0) return(x)
-    x[match(names(replace), x)] <- replace
-  } else if (is.factor(x)) {
-    lev <- levels(x)
-    replace <- replace[names(replace) %in% lev]
-    if (length(replace) == 0) return(x)
-    lev[match(names(replace), lev)] <- replace
-    levels(x) <- lev
-  } else if (!is.null(x)) {
-    stop_input_type(x, "a factor or character vector")
-  }
-  x
-}
-# Iterate through a formula and return a quoted version
-simplify_formula <- function(x) {
-  if (length(x) == 2 && x[[1]] == as.name("~")) {
-    return(simplify(x[[2]]))
-  }
-  if (length(x) < 3)
-    return(list(x))
-  op <- x[[1]]
-  a <- x[[2]]
-  b <- x[[3]]
-  if (op == as.name("+") || op == as.name("*") || op ==
-      as.name("~")) {
-    c(simplify(a), simplify(b))
-  }
-  else if (op == as.name("-")) {
-    c(simplify(a), bquote(-.(x), list(x = simplify(b))))
-  }
-  else {
-    list(x)
-  }
-}
-#' Create a quoted version of x
-#'
-#' This function captures the special meaning of formulas in the context of
-#' facets in ggplot2, where `+` have special meaning. It works as
-#' `plyr::as.quoted` but only for the special cases of `character`, `call`, and
-#' `formula` input as these are the only situations relevant for ggplot2.
-#'
-#' @param x A formula, string, or call to be quoted
-#' @param env The environment to a attach to the quoted expression.
-#'
-#' @keywords internal
-#' @noRd
-#'
-as.quoted <- function(x, env = parent.frame()) {
-  x <- if (is.character(x)) {
-    lapply(x, function(x) parse(text = x)[[1]])
-  } else if (is.formula(x)) {
-    simplify_formula(x)
-  } else if (is.call(x)) {
-    as.list(x)[-1]
-  } else {
-    cli::cli_abort("Must be a character vector, call, or formula.")
-  }
-  attributes(x) <- list(env = env, class = 'quoted')
-  x
-}
+
 # round a number to a given precision
 round_any <- function(x, accuracy, f = round) {
   check_numeric(x)
@@ -286,29 +209,20 @@ dapply <- function(df, by, fun, ..., drop = TRUE) {
   }
 
   # Shortcut when only one group
-  if (all(vapply(grouping_cols, single_value, logical(1)))) {
+  has_single_group <- all(vapply(
+    grouping_cols,
+    function(x) identical(as.character(levels(x) %||% attr(x, "n")), "1"),
+    logical(1)
+  ))
+  if (has_single_group) {
     return(apply_fun(df))
   }
 
   ids <- id(grouping_cols, drop = drop)
   group_rows <- split_with_index(seq_len(nrow(df)), ids)
   result <- lapply(seq_along(group_rows), function(i) {
-    cur_data <- df_rows(df, group_rows[[i]])
+    cur_data <- vec_slice(df, group_rows[[i]])
     apply_fun(cur_data)
   })
   vec_rbind0(!!!result)
 }
-
-single_value <- function(x, ...) {
-  UseMethod("single_value")
-}
-#' @export
-single_value.default <- function(x, ...) {
-  # This is set by id() used in creating the grouping var
-  identical(attr(x, "n"), 1L)
-}
-#' @export
-single_value.factor <- function(x, ...) {
-  # Panels are encoded as factor numbers and can never be missing (NA)
-  identical(levels(x), "1")
-}
diff --git a/R/coord-.R b/R/coord-.R
index 0d0bb5ecb9..64163a772f 100644
--- a/R/coord-.R
+++ b/R/coord-.R
@@ -226,11 +226,18 @@ Coord <- ggproto("Coord",
   }
 )
 
-#' Is this object a coordinate system?
-#'
-#' @export is.Coord
-#' @keywords internal
-is.Coord <- function(x) inherits(x, "Coord")
+
+#' @export
+#' @rdname is_tests
+is.coord <- function(x) inherits(x, "Coord")
+
+#' @export
+#' @rdname is_tests
+#' @usage is.Coord(x) # Deprecated
+is.Coord <- function(x) {
+  deprecate_soft0("3.5.2", "is.Coord()", "is.coord()")
+  is.coord(x)
+}
 
 # Renders an axis with the correct orientation or zeroGrob if no axis should be
 # generated
diff --git a/R/coord-cartesian-.R b/R/coord-cartesian-.R
index 885918c3d1..1b13d9c6c0 100644
--- a/R/coord-cartesian-.R
+++ b/R/coord-cartesian-.R
@@ -163,7 +163,7 @@ view_scales_from_scale <- function(scale, coord_limits = NULL, expand = TRUE) {
 }
 
 panel_guides_grob <- function(guides, position, theme, labels = NULL) {
-  if (!inherits(guides, "Guides")) {
+  if (!is.guides(guides)) {
     return(zeroGrob())
   }
   pair <- guides$get_position(position)
diff --git a/R/coord-map.R b/R/coord-map.R
index d300d33dce..3ba9260206 100644
--- a/R/coord-map.R
+++ b/R/coord-map.R
@@ -157,7 +157,7 @@ CoordMap <- ggproto("CoordMap", Coord,
 
   transform = function(self, data, panel_params) {
     trans <- mproject(self, data$x, data$y, panel_params$orientation)
-    out <- cunion(trans[c("x", "y")], data)
+    out <- data_frame0(!!!defaults(trans[c("x", "y")], data))
 
     out$x <- rescale(out$x, 0:1, panel_params$x.proj)
     out$y <- rescale(out$y, 0:1, panel_params$y.proj)
diff --git a/R/coord-sf.R b/R/coord-sf.R
index f129947dc0..c31af6d393 100644
--- a/R/coord-sf.R
+++ b/R/coord-sf.R
@@ -545,11 +545,7 @@ coord_sf <- function(xlim = NULL, ylim = NULL, expand = TRUE,
     label_axes <- label_axes %|W|% ""
   }
 
-  if (is.character(label_axes)) {
-    label_axes <- parse_axes_labeling(label_axes)
-  } else if (!is.list(label_axes)) {
-    cli::cli_abort("Panel labeling format not recognized.")
-  }
+  label_axes <- parse_axes_labeling(label_axes)
 
   if (is.character(label_graticule)) {
     label_graticule <- unlist(strsplit(label_graticule, ""))
@@ -582,9 +578,14 @@ coord_sf <- function(xlim = NULL, ylim = NULL, expand = TRUE,
   )
 }
 
-parse_axes_labeling <- function(x) {
-  labs <- unlist(strsplit(x, ""))
-  list(top = labs[1], right = labs[2], bottom = labs[3], left = labs[4])
+parse_axes_labeling <- function(x, call = caller_env()) {
+  if (is.character(x)) {
+    x <- unlist(strsplit(x, ""))
+    x <- list(top = x[1], right = x[2], bottom = x[3], left = x[4])
+  } else if (!is.list(x)) {
+    cli::cli_abort("Panel labeling format not recognized.", call = call)
+  }
+  x
 }
 
 # This function does two things differently from standard breaks:
diff --git a/R/facet-.R b/R/facet-.R
index 2e349f6f97..8faafc1428 100644
--- a/R/facet-.R
+++ b/R/facet-.R
@@ -266,6 +266,10 @@ Facet <- ggproto("Facet", NULL,
   }
 )
 
+#' @export
+#' @rdname is_tests
+is.facet <- function(x) inherits(x, "Facet")
+
 # Helpers -----------------------------------------------------------------
 
 #' Quote faceting variables
@@ -353,13 +357,6 @@ get_strip_labels <- function(plot = get_last_plot()) {
   plot$plot$facet$format_strip_labels(layout, params)
 }
 
-#' Is this object a faceting specification?
-#'
-#' @param x object to test
-#' @keywords internal
-#' @export
-is.facet <- function(x) inherits(x, "Facet")
-
 # A "special" value, currently not used but could be used to determine
 # if faceting is active
 NO_PANEL <- -1L
@@ -418,7 +415,14 @@ as_facets_list <- function(x) {
   # distinct facet dimensions and `+` defines multiple facet variables
   # inside each dimension.
   if (is_formula(x)) {
-    return(f_as_facets_list(x))
+    if (length(x) == 2) {
+      rows <- f_as_facets(NULL)
+      cols <- f_as_facets(x)
+    } else {
+      rows <- f_as_facets(x[-3])
+      cols <- f_as_facets(x[-2])
+    }
+    return(list(rows, cols))
   }
 
   # For backward-compatibility with facet_wrap()
@@ -437,7 +441,7 @@ as_facets_list <- function(x) {
 }
 
 validate_facets <- function(x) {
-  if (inherits(x, "uneval")) {
+  if (is.mapping(x)) {
     cli::cli_abort("Please use {.fn vars} to supply facet variables.")
   }
   # Native pipe have higher precedence than + so any type of gg object can be
@@ -451,10 +455,9 @@ validate_facets <- function(x) {
   x
 }
 
-
 # Flatten a list of quosures objects to a quosures object, and compact it
 compact_facets <- function(x) {
-
+  x <- as_facets_list(x)
   proxy   <- vec_proxy(x)
   is_list <- vapply(proxy, vec_is_list, logical(1))
   proxy[is_list]  <- lapply(proxy[is_list],  unclass)
@@ -501,18 +504,10 @@ simplify <- function(x) {
   }
 }
 
-f_as_facets_list <- function(f) {
-  lhs <- function(x) if (length(x) == 2) NULL else x[-3]
-  rhs <- function(x) if (length(x) == 2) x else x[-2]
-
-  rows <- f_as_facets(lhs(f))
-  cols <- f_as_facets(rhs(f))
-
-  list(rows, cols)
-}
-
 as_facets <- function(x) {
-  if (is_facets(x)) {
+  is_facets <- is.list(x) && length(x) > 0 &&
+    all(vapply(x, is_quosure, logical(1)))
+  if (is_facets) {
     return(x)
   }
 
@@ -533,27 +528,13 @@ f_as_facets <- function(f) {
   env <- f_env(f) %||% globalenv()
 
   # as.quoted() handles `+` specifications
-  vars <- as.quoted(f)
+  vars <- simplify(f)
 
-  # `.` in formulas is ignored
-  vars <- discard_dots(vars)
+  # `.` in formulas is discarded
+  vars <- vars[!vapply(vars, identical, logical(1), as.name("."))]
 
   as_quosures(vars, env, named = TRUE)
 }
-discard_dots <- function(x) {
-  x[!vapply(x, identical, logical(1), as.name("."))]
-}
-
-is_facets <- function(x) {
-  if (!is.list(x)) {
-    return(FALSE)
-  }
-  if (!length(x)) {
-    return(FALSE)
-  }
-  all(vapply(x, is_quosure, logical(1)))
-}
-
 
 # When evaluating variables in a facet specification, we evaluate bare
 # variables and expressions slightly differently. Bare variables should
diff --git a/R/facet-grid-.R b/R/facet-grid-.R
index a0b6e31931..784e394885 100644
--- a/R/facet-grid-.R
+++ b/R/facet-grid-.R
@@ -219,8 +219,8 @@ grid_as_facets_list <- function(rows, cols) {
   check_object(cols, is_quosures, "a {.fn vars} specification", allow_null = TRUE)
 
   list(
-    rows = compact_facets(as_facets_list(rows)),
-    cols = compact_facets(as_facets_list(cols))
+    rows = compact_facets(rows),
+    cols = compact_facets(cols)
   )
 }
 
diff --git a/R/facet-wrap.R b/R/facet-wrap.R
index 8564f319b7..4650d12dd8 100644
--- a/R/facet-wrap.R
+++ b/R/facet-wrap.R
@@ -177,7 +177,7 @@ facet_wrap <- function(facets, nrow = NULL, ncol = NULL, scales = "fixed",
   labeller <- check_labeller(labeller)
 
   # Flatten all facets dimensions into a single one
-  facets <- wrap_as_facets_list(facets)
+  facets <- compact_facets(facets)
 
   if (lifecycle::is_present(switch) && !is.null(switch)) {
     deprecate_warn0("2.2.0", "facet_wrap(switch)", "facet_wrap(strip.position)")
@@ -213,12 +213,6 @@ facet_wrap <- function(facets, nrow = NULL, ncol = NULL, scales = "fixed",
   )
 }
 
-# Returns a quosures object
-wrap_as_facets_list <- function(x) {
-  facets_list <- as_facets_list(x)
-  compact_facets(facets_list)
-}
-
 #' @rdname ggplot2-ggproto
 #' @format NULL
 #' @usage NULL
diff --git a/R/fortify.R b/R/fortify.R
index 5b5b7c5171..da4bcf7892 100644
--- a/R/fortify.R
+++ b/R/fortify.R
@@ -82,7 +82,7 @@ fortify.default <- function(model, data, ...) {
     "or an object coercible by {.fn fortify}, or a valid ",
     "{.cls data.frame}-like object coercible by {.fn as.data.frame}"
   )
-  if (inherits(model, "uneval")) {
+  if (is.mapping(model)) {
     msg <- c(
       paste0(msg, ", not ", obj_type_friendly(model), "."),
       "i" = "Did you accidentally pass {.fn aes} to the {.arg data} argument?"
diff --git a/R/geom-.R b/R/geom-.R
index 5b6a2af09d..c5a1ab275d 100644
--- a/R/geom-.R
+++ b/R/geom-.R
@@ -183,7 +183,7 @@ Geom <- ggproto("Geom",
 
       modified_aes <- data_frame0(!!!compact(modified_aes))
 
-      data <- cunion(modified_aes, data)
+      data <- data_frame0(!!!defaults(modified_aes, data))
     }
 
     # Override mappings with params
@@ -236,6 +236,9 @@ Geom <- ggproto("Geom",
 
 )
 
+#' @export
+#' @rdname is_tests
+is.geom <- function(x) inherits(x, "Geom")
 
 eval_from_theme <- function(aesthetics, theme) {
   themed <- is_themed_aes(aesthetics)
diff --git a/R/geom-defaults.R b/R/geom-defaults.R
index 65974f841a..b185990fbb 100644
--- a/R/geom-defaults.R
+++ b/R/geom-defaults.R
@@ -98,7 +98,7 @@ get_geom_defaults <- function(geom, theme = theme_get()) {
   if (is.character(geom)) {
     geom <- check_subclass(geom, "Geom")
   }
-  if (inherits(geom, "Geom")) {
+  if (is.geom(geom)) {
     out <- geom$use_defaults(data = NULL, theme = theme)
     return(out)
   }
diff --git a/R/geom-hex.R b/R/geom-hex.R
index 6badb8f87a..152227a40b 100644
--- a/R/geom-hex.R
+++ b/R/geom-hex.R
@@ -118,34 +118,3 @@ GeomHex <- ggproto("GeomHex", Geom,
 
   rename_size = TRUE
 )
-
-
-# Draw hexagon grob
-# Modified from code by Nicholas Lewin-Koh and Martin Maechler
-#
-# @param x positions of hex centres
-# @param y positions
-# @param size vector of hex sizes
-# @param gp graphical parameters
-# @keyword internal
-#
-# THIS IS NO LONGER USED BUT LEFT IF CODE SOMEWHERE ELSE RELIES ON IT
-hexGrob <- function(x, y, size = rep(1, length(x)), gp = gpar()) {
-  if (length(y) != length(x)) {
-    cli::cli_abort("{.arg x} and {.arg y} must have the same length")
-  }
-
-  dx <- resolution(x, FALSE)
-  dy <- resolution(y, FALSE) / sqrt(3) / 2 * 1.15
-
-  hexC <- hexbin::hexcoords(dx, dy, n = 1)
-
-  n <- length(x)
-
-  polygonGrob(
-    x = rep.int(hexC$x, n) * rep(size, each = 6) + rep(x, each = 6),
-    y = rep.int(hexC$y, n) * rep(size, each = 6) + rep(y, each = 6),
-    default.units = "native",
-    id.lengths = rep(6, n), gp = gp
-  )
-}
diff --git a/R/geom-label.R b/R/geom-label.R
index 4168c98d94..6f21478da0 100644
--- a/R/geom-label.R
+++ b/R/geom-label.R
@@ -78,7 +78,7 @@ GeomLabel <- ggproto("GeomLabel", Geom,
     data <- coord$transform(data, panel_params)
     data$vjust <- compute_just(data$vjust, data$y, data$x, data$angle)
     data$hjust <- compute_just(data$hjust, data$x, data$y, data$angle)
-    if (!inherits(label.padding, "margin")) {
+    if (!is.margin("margin")) {
       label.padding <- rep(label.padding, length.out = 4)
     }
 
diff --git a/R/geom-violin.R b/R/geom-violin.R
index 17a2d40e94..9976e5b8a4 100644
--- a/R/geom-violin.R
+++ b/R/geom-violin.R
@@ -223,7 +223,7 @@ create_quantile_segment_frame <- function(data, draw_quantiles) {
 
   # We have two rows per segment drawn. Each segment gets its own group.
   data_frame0(
-    x = interleave(violin.xminvs, violin.xmaxvs),
+    x = vec_interleave(violin.xminvs, violin.xmaxvs),
     y = rep(ys, each = 2),
     group = rep(ys, each = 2)
   )
diff --git a/R/ggproto.R b/R/ggproto.R
index 0af8a5a5ab..6165a9707d 100644
--- a/R/ggproto.R
+++ b/R/ggproto.R
@@ -98,6 +98,9 @@ ggproto <- function(`_class` = NULL, `_inherit` = NULL, ...) {
   e
 }
 
+#' @export
+#' @rdname is_tests
+is.ggproto <- function(x) inherits(x, "ggproto")
 
 #' @export
 #' @rdname ggproto
@@ -106,11 +109,6 @@ ggproto_parent <- function(parent, self) {
   structure(list(parent = parent, self = self), class = "ggproto_parent")
 }
 
-#' @param x An object to test.
-#' @export
-#' @rdname ggproto
-is.ggproto <- function(x) inherits(x, "ggproto")
-
 fetch_ggproto <- function(x, name) {
   res <- NULL
 
diff --git a/R/grob-dotstack.R b/R/grob-dotstack.R
index 75ca9e81ed..d3463c18bd 100644
--- a/R/grob-dotstack.R
+++ b/R/grob-dotstack.R
@@ -14,15 +14,13 @@ dotstackGrob <- function(
         y <- unit(y, default.units)
     if (!is.unit(dotdia))
         dotdia <- unit(dotdia, default.units)
-    if (!is_npc(dotdia))
+    if (!unitType(dotdia) == "npc")
         cli::cli_warn("Unit type of dotdia should be {.val npc}")
 
     grob(x = x, y = y, stackaxis = stackaxis, dotdia = dotdia,
          stackposition = stackposition, stackdir = stackdir, stackratio = stackratio,
          name = name, gp = gp, vp = vp, cl = "dotstackGrob")
 }
-# Only cross-version reliable way to check the unit of a unit object
-is_npc <- function(x) isTRUE(grepl('^[^+^-^\\*]*[^s]npc$', as.character(x)))
 
 #' @export
 makeContext.dotstackGrob <- function(x) {
diff --git a/R/guide-.R b/R/guide-.R
index 4cb77ee7bb..dd63949cd2 100644
--- a/R/guide-.R
+++ b/R/guide-.R
@@ -66,6 +66,10 @@ new_guide <- function(..., available_aes = "any", super) {
   )
 }
 
+#' @export
+#' @rdname is_tests
+is.guide <- function(x) inherits(x, "Guide")
+
 #' @section Guides:
 #'
 #' The `guide_*()` functions, such as `guide_legend()` return an object that
@@ -377,7 +381,7 @@ Guide <- ggproto(
   # Renders tickmarks
   build_ticks = function(key, elements, params, position = params$position,
                          length = elements$ticks_length) {
-    if (!inherits(elements, "element")) {
+    if (!is.element(elements)) {
       elements <- elements$ticks
     }
     if (!inherits(elements, "element_line")) {
@@ -519,7 +523,8 @@ opposite_position <- function(position) {
     top    = "bottom",
     bottom = "top",
     left   = "right",
-    right  = "left"
+    right  = "left",
+    position
   )
 }
 
diff --git a/R/guides-.R b/R/guides-.R
index fcd65bb94a..d250c78025 100644
--- a/R/guides-.R
+++ b/R/guides-.R
@@ -69,7 +69,7 @@ NULL
 guides <- function(...) {
   args <- list2(...)
   if (length(args) > 0) {
-    if (is.list(args[[1]]) && !inherits(args[[1]], "guide")) args <- args[[1]]
+    if (is.list(args[[1]]) && !is.guide(args[[1]])) args <- args[[1]]
     args <- rename_aes(args)
   }
 
@@ -109,18 +109,9 @@ guides <- function(...) {
   NULL
 }
 
-update_guides <- function(p, guides) {
-  p <- plot_clone(p)
-  if (inherits(p$guides, "Guides")) {
-    old <- p$guides
-    new <- ggproto(NULL, old)
-    new$add(guides)
-    p$guides <- new
-  } else {
-    p$guides <- guides
-  }
-  p
-}
+#' @export
+#' @rdname is_tests
+is.guides <- function(x) inherits(x, "Guides")
 
 # Class -------------------------------------------------------------------
 
@@ -151,7 +142,7 @@ Guides <- ggproto(
     if (is.null(guides)) {
       return(invisible())
     }
-    if (inherits(guides, "Guides")) {
+    if (is.guides(guides)) {
       guides <- guides$guides
     }
     self$guides <- defaults(guides, self$guides)
@@ -350,13 +341,8 @@ Guides <- ggproto(
       # Find guide for aesthetic-scale combination
       # Hierarchy is in the order:
       # plot + guides(XXX) + scale_ZZZ(guide = XXX) > default(i.e., legend)
-      guide <- resolve_guide(
-        aesthetic = aesthetics[idx],
-        scale     = scales[[idx]],
-        guides    = guides,
-        default   = default,
-        null      = missing
-      )
+      guide <- guides[[aesthetics[idx]]] %||% scales[[idx]]$guide %|W|%
+        default %||% missing
 
       if (isFALSE(guide)) {
         deprecate_warn0("3.3.4", I("The `guide` argument in `scale_*()` cannot be `FALSE`. This "), I('"none"'))
@@ -870,24 +856,6 @@ include_layer_in_guide <- function(layer, matched) {
   isTRUE(layer$show.legend)
 }
 
-# Simplify legend position to one of horizontal/vertical/inside
-legend_position <- function(position) {
-  if (length(position) == 1) {
-    if (position %in% c("top", "bottom")) {
-      "horizontal"
-    } else {
-      "vertical"
-    }
-  } else {
-    "inside"
-  }
-}
-
-# resolve the guide from the scale and guides
-resolve_guide <- function(aesthetic, scale, guides, default = "none", null = "none") {
-  guides[[aesthetic]] %||% scale$guide %|W|% default %||% null
-}
-
 # validate guide object
 validate_guide <- function(guide) {
   # if guide is specified by character, then find the corresponding guide
@@ -898,7 +866,7 @@ validate_guide <- function(guide) {
       guide <- fun()
     }
   }
-  if (inherits(guide, "Guide")) {
+  if (is.guide(guide)) {
     return(guide)
   }
   if (inherits(guide, "guide") && is.list(guide)) {
diff --git a/R/labeller.R b/R/labeller.R
index f23f22b459..4ca220c2b4 100644
--- a/R/labeller.R
+++ b/R/labeller.R
@@ -114,21 +114,17 @@ label_value <- function(labels, multi_line = TRUE) {
 # currently needed for Roxygen
 class(label_value) <- c("function", "labeller")
 
-# Helper for label_both
-label_variable <- function(labels, multi_line = TRUE) {
-  if (multi_line) {
-    row <- as.list(names(labels))
-  } else {
-    row <- list(paste(names(labels), collapse = ", "))
-  }
-  lapply(row, rep, nrow(labels) %||% length(labels[[1]]))
-}
-
 #' @rdname labellers
 #' @export
 label_both <- function(labels, multi_line = TRUE, sep = ": ") {
   value <- label_value(labels, multi_line = multi_line)
-  variable <- label_variable(labels, multi_line = multi_line)
+
+  if (isTRUE(multi_line)) {
+    row <- as.list(names(labels))
+  } else {
+    row <- list(paste(names(labels), collapse = ", "))
+  }
+  variable <- lapply(row, rep, nrow(labels) %||% length(labels[[1]]))
 
   if (multi_line) {
     out <- vector("list", length(value))
@@ -176,14 +172,6 @@ label_parsed <- function(labels, multi_line = TRUE) {
 }
 class(label_parsed) <- c("function", "labeller")
 
-find_names <- function(expr) {
-  if (is.call(expr)) {
-    unlist(lapply(expr[-1], find_names))
-  } else if (is.name(expr)) {
-    as.character(expr)
-  }
-}
-
 #' Label with mathematical expressions
 #'
 #' `label_bquote()` offers a flexible way of labelling
diff --git a/R/layer.R b/R/layer.R
index 8acb438c9e..3fd89cf3f7 100644
--- a/R/layer.R
+++ b/R/layer.R
@@ -58,8 +58,8 @@
 #'   `NA`, the default, includes if any aesthetics are mapped.
 #'   `FALSE` never includes, and `TRUE` always includes.
 #'   It can also be a named logical vector to finely select the aesthetics to
-#'   display. To include legend keys for all levels, even 
-#'   when no data exists, use `TRUE`.  If `NA`, all levels are shown in legend, 
+#'   display. To include legend keys for all levels, even
+#'   when no data exists, use `TRUE`.  If `NA`, all levels are shown in legend,
 #'   but unobserved levels are omitted.
 #' @param inherit.aes If `FALSE`, overrides the default aesthetics,
 #'   rather than combining with them. This is most useful for helper functions
@@ -202,8 +202,12 @@ layer <- function(geom = NULL, stat = NULL,
   )
 }
 
+#' @export
+#' @rdname is_tests
+is.layer <- function(x) inherits(x, "Layer")
+
 validate_mapping <- function(mapping, call = caller_env()) {
-  if (!inherits(mapping, "uneval")) {
+  if (!is.mapping(mapping)) {
     msg <- "{.arg mapping} must be created by {.fn aes}."
     # Native pipe have higher precedence than + so any type of gg object can be
     # expected here, not just ggplot
@@ -419,7 +423,7 @@ Layer <- ggproto("Layer", NULL,
     }
     stat_data <- cleanup_mismatched_data(stat_data, nrow(data), "after_stat")
 
-    cunion(stat_data, data)
+    data_frame0(!!!defaults(stat_data, data))
   },
 
   compute_geom_1 = function(self, data) {
@@ -468,8 +472,6 @@ Layer <- ggproto("Layer", NULL,
   }
 )
 
-is.layer <- function(x) inherits(x, "Layer")
-
 check_subclass <- function(x, subclass,
                            argname = to_lower_ascii(subclass),
                            env = parent.frame(),
diff --git a/R/limits.R b/R/limits.R
index 087c4c11d0..2e31220ec8 100644
--- a/R/limits.R
+++ b/R/limits.R
@@ -80,7 +80,7 @@
 lims <- function(...) {
   args <- list2(...)
 
-  if (!all(has_name(args))) {
+  if (!is_named2(args)) {
     cli::cli_abort("All arguments must be named.")
   }
   env <- current_env()
diff --git a/R/margins.R b/R/margins.R
index 176072b4de..7104a7d330 100644
--- a/R/margins.R
+++ b/R/margins.R
@@ -8,9 +8,10 @@ margin <- function(t = 0, r = 0, b = 0, l = 0, unit = "pt") {
   class(u) <- c("margin", class(u))
   u
 }
-is.margin <- function(x) {
-  inherits(x, "margin")
-}
+
+#' @export
+#' @rdname is_tests
+is.margin <- function(x) inherits(x, "margin")
 
 #' Create a text grob with the proper location and margins
 #'
@@ -151,82 +152,6 @@ heightDetails.titleGrob <- function(x) {
   sum(x$heights)
 }
 
-#' Justifies a grob within a larger drawing area
-#'
-#' `justify_grobs()` can be used to take one or more grobs and draw them justified inside a larger
-#' drawing area, such as the cell in a gtable. It is needed to correctly place [`titleGrob`]s
-#' with margins.
-#'
-#' @param grobs The single grob or list of grobs to justify.
-#' @param x,y x and y location of the reference point relative to which justification
-#'   should be performed. If `NULL`, justification will be done relative to the
-#'   enclosing drawing area (i.e., `x = hjust` and `y = vjust`).
-#' @param hjust,vjust Horizontal and vertical justification of the grob relative to `x` and `y`.
-#' @param int_angle Internal angle of the grob to be justified. When justifying a text
-#'   grob with rotated text, this argument can be used to make `hjust` and `vjust` operate
-#'   relative to the direction of the text.
-#' @param debug If `TRUE`, aids visual debugging by drawing a solid
-#'   rectangle behind the complete grob area.
-#'
-#' @noRd
-justify_grobs <- function(grobs, x = NULL, y = NULL, hjust = 0.5, vjust = 0.5,
-                          int_angle = 0, debug = FALSE) {
-  if (!inherits(grobs, "grob")) {
-    if (is.list(grobs)) {
-      return(lapply(grobs, justify_grobs, x, y, hjust, vjust, int_angle, debug))
-    }
-    else {
-      stop_input_type(grobs, as_cli("an individual {.cls grob} or list of {.cls grob} objects"))
-    }
-  }
-
-  if (inherits(grobs, "zeroGrob")) {
-    return(grobs)
-  }
-
-  # adjust hjust and vjust according to internal angle
-  just <- rotate_just(int_angle, hjust, vjust)
-
-  x <- x %||% unit(just$hjust, "npc")
-  y <- y %||% unit(just$vjust, "npc")
-
-
-  if (isTRUE(debug)) {
-    children <- gList(
-      rectGrob(gp = gg_par(fill = "lightcyan", col = NA)),
-      grobs
-    )
-  }
-  else {
-    children <- gList(grobs)
-  }
-
-
-  result_grob <- gTree(
-    children = children,
-    vp = viewport(
-      x = x,
-      y = y,
-      width = grobWidth(grobs),
-      height = grobHeight(grobs),
-      just = unlist(just)
-    )
-  )
-
-
-  if (isTRUE(debug)) {
-    #cat("x, y:", c(x, y), "\n")
-    #cat("E - hjust, vjust:", c(hjust, vjust), "\n")
-    grobTree(
-      result_grob,
-      pointsGrob(x, y, pch = 20, gp = gg_par(col = "mediumturquoise"))
-    )
-  } else {
-    result_grob
-  }
-}
-
-
 #' Rotate justification parameters counter-clockwise
 #'
 #' @param angle angle of rotation, in degrees
diff --git a/R/performance.R b/R/performance.R
index b26b1a7072..7676ed31d6 100644
--- a/R/performance.R
+++ b/R/performance.R
@@ -10,13 +10,6 @@ mat_2_df <- function(x, col_names = colnames(x)) {
   data_frame0(!!!cols, .size = nrow(x))
 }
 
-df_col <- function(x, name) .subset2(x, name)
-
-df_rows <- function(x, i) {
-  cols <- lapply(x, `[`, i = i)
-  data_frame0(!!!cols, .size = length(i))
-}
-
 # More performant modifyList without recursion
 modify_list <- function(old, new) {
   for (i in names(new)) old[[i]] <- new[[i]]
diff --git a/R/plot-build.R b/R/plot-build.R
index 36f33616fd..c7e641c8e6 100644
--- a/R/plot-build.R
+++ b/R/plot-build.R
@@ -288,7 +288,7 @@ ggplot_gtable.ggplot_built <- function(data) {
   plot_margin <- calc_element("plot.margin", theme)
   plot_table  <- gtable_add_padding(plot_table, plot_margin)
 
-  if (inherits(theme$plot.background, "element")) {
+  if (is.element(theme$plot.background)) {
     plot_table <- gtable_add_grob(plot_table,
       element_render(theme, "plot.background"),
       t = 1, l = 1, b = -1, r = -1, name = "background", z = -Inf)
@@ -408,11 +408,10 @@ table_add_tag <- function(table, label, theme) {
       x <- unit(position[1], "npc")
       y <- unit(position[2], "npc")
     }
-    # Do manual placement of tag
-    tag <- justify_grobs(
-      tag, x = x, y = y,
-      hjust = element$hjust, vjust = element$vjust,
-      int_angle = element$angle, debug = element$debug
+    # Re-render with manual positions
+    tag <- element_grob(
+      element, x = x, y = y, label = label,
+      margin_y = TRUE, margin_x = TRUE
     )
     if (location == "plot") {
       table <- gtable_add_grob(
diff --git a/R/plot-construction.R b/R/plot-construction.R
index 14f2badaed..ac0619cbdb 100644
--- a/R/plot-construction.R
+++ b/R/plot-construction.R
@@ -149,7 +149,16 @@ ggplot_add.labels <- function(object, plot, object_name) {
 }
 #' @export
 ggplot_add.Guides <- function(object, plot, object_name) {
-  update_guides(plot, object)
+  if (is.guides(plot$guides)) {
+    # We clone the guides object to prevent modify-in-place of guides
+    old <- plot$guides
+    new <- ggproto(NULL, old)
+    new$add(object)
+    plot$guides <- new
+  } else {
+    plot$guides <- object
+  }
+  plot
 }
 #' @export
 ggplot_add.uneval <- function(object, plot, object_name) {
diff --git a/R/plot.R b/R/plot.R
index 6bdcabc23f..95c7f2f8a0 100644
--- a/R/plot.R
+++ b/R/plot.R
@@ -111,7 +111,7 @@ ggplot <- function(data = NULL, mapping = aes(), ...,
 #' @export
 ggplot.default <- function(data = NULL, mapping = aes(), ...,
                            environment = parent.frame()) {
-  if (!missing(mapping) && !inherits(mapping, "uneval")) {
+  if (!missing(mapping) && !is.mapping(mapping)) {
     cli::cli_abort(c(
       "{.arg mapping} must be created with {.fn aes}.",
       "x" = "You've supplied {.obj_type_friendly {mapping}}."
@@ -147,6 +147,13 @@ ggplot.function <- function(data = NULL, mapping = aes(), ...,
   ))
 }
 
+#' Reports whether x is a type of object
+#' @param x An object to test
+#' @keywords internal
+#' @export
+#' @name is_tests
+is.ggplot <- function(x) inherits(x, "ggplot")
+
 plot_clone <- function(plot) {
   p <- plot
   p$scales <- plot$scales$clone()
@@ -154,12 +161,6 @@ plot_clone <- function(plot) {
   p
 }
 
-#' Reports whether x is a ggplot object
-#' @param x An object to test
-#' @keywords internal
-#' @export
-is.ggplot <- function(x) inherits(x, "ggplot")
-
 #' Explicitly draw plot
 #'
 #' Generally, you do not need to print or plot a ggplot2 plot explicitly: the
diff --git a/R/position-.R b/R/position-.R
index 559c6c68d0..88d6f914a9 100644
--- a/R/position-.R
+++ b/R/position-.R
@@ -69,6 +69,10 @@ Position <- ggproto("Position",
   }
 )
 
+#' @export
+#' @rdname is_tests
+is.position <- function(x) inherits(x, "Position")
+
 #' Convenience function to transform all position variables.
 #'
 #' @param trans_x,trans_y Transformation functions for x and y aesthetics.
diff --git a/R/quick-plot.R b/R/quick-plot.R
index 0ef5852cfb..38cfd895fc 100644
--- a/R/quick-plot.R
+++ b/R/quick-plot.R
@@ -173,8 +173,3 @@ qplot <- function(x, y, ..., data, facets = NULL, margins = FALSE,
 #' @export
 #' @rdname qplot
 quickplot <- qplot
-
-is.constant <- function(x) {
-  is_I_call <- function(x) is.call(x) && identical(x[[1]], quote(I))
-  vapply(x, is_I_call, logical(1))
-}
diff --git a/R/save.R b/R/save.R
index acc4176162..ffe6945410 100644
--- a/R/save.R
+++ b/R/save.R
@@ -182,7 +182,7 @@ parse_dpi <- function(dpi, call = caller_env()) {
       print = 300,
       retina = 320,
     )
-  } else if (is_scalar_numeric(dpi)) {
+  } else if (is_bare_numeric(dpi, n = 1L)) {
     dpi
   } else {
     stop_input_type(dpi, "a single number or string", call = call)
diff --git a/R/scale-.R b/R/scale-.R
index fd0bbd444f..878cc602b9 100644
--- a/R/scale-.R
+++ b/R/scale-.R
@@ -357,6 +357,10 @@ binned_scale <- function(aesthetics, scale_name = deprecated(), palette, name =
   )
 }
 
+#' @export
+#' @rdname is_tests
+is.scale <- function(x) inherits(x, "Scale")
+
 #' @section Scales:
 #'
 #' All `scale_*` functions like [scale_x_continuous()] return a `Scale*`
@@ -1379,13 +1383,7 @@ ScaleBinned <- ggproto("ScaleBinned", Scale,
 
 # In place modification of a scale to change the primary axis
 scale_flip_position <- function(scale) {
-  scale$position <- switch(scale$position,
-    top = "bottom",
-    bottom = "top",
-    left = "right",
-    right = "left",
-    scale$position
-  )
+  scale$position <- opposite_position(scale$position)
   invisible()
 }
 
diff --git a/R/scale-colour.R b/R/scale-colour.R
index 71255e2033..19cdda1396 100644
--- a/R/scale-colour.R
+++ b/R/scale-colour.R
@@ -197,7 +197,7 @@ scale_fill_binned <- function(...,
 # helper function to make sure that the provided scale is of the correct
 # type (i.e., is continuous and works with the provided aesthetic)
 check_scale_type <- function(scale, name, aesthetic, scale_is_discrete = FALSE, call = caller_env()) {
-  if (!is.ggproto(scale) || !inherits(scale, "Scale")) {
+  if (!is.ggproto(scale) || !is.scale(scale)) {
     cli::cli_abort(c(
       "The {.arg type} argument must return a continuous scale for the {.field {aesthetic}} aesthetic.",
       "x" = "The provided object is not a scale function."
diff --git a/R/scale-view.R b/R/scale-view.R
index de78ebffb6..3cf18147ec 100644
--- a/R/scale-view.R
+++ b/R/scale-view.R
@@ -90,23 +90,6 @@ view_scale_secondary <- function(scale, limits = scale$get_limits(),
   }
 }
 
-view_scale_empty <- function() {
-  ggproto(NULL, ViewScale,
-    is_empty = function() TRUE,
-    is_discrete = function() NA,
-    dimension = function() c(0, 1),
-    get_limits = function() c(0, 1),
-    get_breaks = function() NULL,
-    get_breaks_minor = function() NULL,
-    get_labels = function(breaks = NULL) breaks,
-    rescale = function(x) cli::cli_abort("Not implemented."),
-    map = function(x) cli::cli_abort("Not implemented."),
-    make_title = function(title) title,
-    break_positions = function() NULL,
-    break_positions_minor = function() NULL
-  )
-}
-
 ViewScale <- ggproto("ViewScale", NULL,
   # map, rescale, and make_title need a reference
   # to the original scale
diff --git a/R/stat-.R b/R/stat-.R
index 2d56937b06..11cdbc67d6 100644
--- a/R/stat-.R
+++ b/R/stat-.R
@@ -218,3 +218,7 @@ Stat <- ggproto("Stat",
   }
 
 )
+
+#' @export
+#' @rdname is_tests
+is.stat <- function(x) inherits(x, "Stat")
diff --git a/R/stat-bin2d.R b/R/stat-bin2d.R
index 69f57ebee3..bdb69db23a 100644
--- a/R/stat-bin2d.R
+++ b/R/stat-bin2d.R
@@ -104,7 +104,7 @@ dual_param <- function(x, default = list(x = NULL, y = NULL)) {
 }
 
 bin2d_breaks <- function(scale, breaks = NULL, origin = NULL, binwidth = NULL,
-                      bins = 30, right = TRUE) {
+                      bins = 30, closed = "right") {
   # Bins for categorical data should take the width of one level,
   # and should show up centered over their tick marks. All other parameters
   # are ignored.
@@ -138,18 +138,7 @@ bin2d_breaks <- function(scale, breaks = NULL, origin = NULL, binwidth = NULL,
   if (length(breaks) > 1 && breaks[length(breaks) - 1] >= range[2]) {
     breaks <- breaks[-length(breaks)]
   }
-
-  adjust_breaks(breaks, right)
-}
-
-adjust_breaks <- function(x, right = TRUE) {
-  diddle <- 1e-07 * stats::median(diff(x))
-  if (right) {
-    fuzz <- c(-diddle, rep.int(diddle, length(x) - 1))
-  } else {
-    fuzz <- c(rep.int(-diddle, length(x) - 1), diddle)
-  }
-  sort(x) + fuzz
+  bins(breaks, closed)$fuzzy
 }
 
 bin_loc <- function(x, id) {
diff --git a/R/stat-summary-bin.R b/R/stat-summary-bin.R
index d94b6ddab9..a56bea189e 100644
--- a/R/stat-summary-bin.R
+++ b/R/stat-summary-bin.R
@@ -82,7 +82,8 @@ StatSummaryBin <- ggproto("StatSummaryBin", Stat,
                            flipped_aes = FALSE, width = NULL) {
     data <- flip_data(data, flipped_aes)
     x <- flipped_names(flipped_aes)$x
-    breaks <- bin2d_breaks(scales[[x]], breaks, origin, binwidth, bins, right = right)
+    breaks <- bin2d_breaks(scales[[x]], breaks, origin, binwidth, bins,
+                           closed = if (right) "right" else "left")
 
     data$bin <- cut(data$x, breaks, include.lowest = TRUE, labels = FALSE)
     out <- dapply(data, "bin", fun %||% function(df) mean_se(df$y))
diff --git a/R/stat-summary.R b/R/stat-summary.R
index 6476021fc5..a32eda8ca0 100644
--- a/R/stat-summary.R
+++ b/R/stat-summary.R
@@ -222,6 +222,16 @@ summarise_by_x <- function(data, summary, ...) {
   merge(summary, unique, by = c("x", "group"), sort = FALSE)
 }
 
+# Return unique columns
+# This is used for figuring out which columns are constant within a group
+#
+# @keyword internal
+uniquecols <- function(df) {
+  df <- df[1, sapply(df, is_unique), drop = FALSE]
+  attr(df, "row.names") <- .set_row_names(nrow(df))
+  df
+}
+
 #' A selection of summary functions from Hmisc
 #'
 #' @description
diff --git a/R/theme-elements.R b/R/theme-elements.R
index 747bb0cf78..7e5de2f777 100644
--- a/R/theme-elements.R
+++ b/R/theme-elements.R
@@ -202,6 +202,10 @@ element_geom <- function(
   pointsize = 1.5, pointshape = 19
 )
 
+#' @export
+#' @rdname is_tests
+is.element <- function(x) inherits(x, "element")
+
 #' @export
 print.element <- function(x, ...) utils::str(x)
 
diff --git a/R/theme.R b/R/theme.R
index 43c379f9b6..2eedd300c5 100644
--- a/R/theme.R
+++ b/R/theme.R
@@ -529,7 +529,7 @@ theme <- function(...,
   # If complete theme set all non-blank elements to inherit from blanks
   if (complete) {
     elements <- lapply(elements, function(el) {
-      if (inherits(el, "element") && !inherits(el, "element_blank")) {
+      if (is.element(el) && !inherits(el, "element_blank")) {
         el$inherit.blank <- TRUE
       }
       el
@@ -543,6 +543,10 @@ theme <- function(...,
   )
 }
 
+#' @export
+#' @rdname is_tests
+is.theme <- function(x) inherits(x, "theme")
+
 # check whether theme is complete
 is_theme_complete <- function(x) isTRUE(attr(x, "complete", exact = TRUE))
 
@@ -894,7 +898,9 @@ combine_elements <- function(e1, e2) {
   }
 
   # If e2 is 'richer' than e1, fill e2 with e1 parameters
-  if (is.subclass(e2, e1)) {
+  is_subclass <- !any(inherits(e2, class(e1), which = TRUE) == 0)
+  is_subclass <- is_subclass && length(setdiff(class(e2), class(e1)) > 0)
+  if (is_subclass) {
     new <- defaults(e1, e2)
     e2[names(new)] <- new
     return(e2)
@@ -903,17 +909,6 @@ combine_elements <- function(e1, e2) {
   e1
 }
 
-is.subclass <- function(x, y) {
-  inheritance <- inherits(x, class(y), which = TRUE)
-  !any(inheritance == 0) && length(setdiff(class(x), class(y))) > 0
-}
-
-#' Reports whether x is a theme object
-#' @param x An object to test
-#' @export
-#' @keywords internal
-is.theme <- function(x) inherits(x, "theme")
-
 #' @export
 `$.theme` <- function(x, ...) {
   .subset2(x, ...)
diff --git a/R/utilities-break.R b/R/utilities-break.R
index 0ed711ad7a..11bc22019d 100644
--- a/R/utilities-break.R
+++ b/R/utilities-break.R
@@ -79,8 +79,8 @@ cut_width <- function(x, width, center = NULL, boundary = NULL, closed = "right"
   }
   boundary <- as.numeric(boundary)
 
-  # Determine bins
-  min_x <- find_origin(x_range, width, boundary)
+  # Determine bins, find origin
+  min_x <- boundary + floor((x_range[1] - boundary) / width) * width
   # Small correction factor so that we don't get an extra bin when, for
   # example, origin = 0, max(x) = 20, width = 10.
   max_x <- max(x, na.rm = TRUE) + (1 - 1e-08) * width
@@ -89,12 +89,6 @@ cut_width <- function(x, width, center = NULL, boundary = NULL, closed = "right"
   cut(x, breaks, include.lowest = TRUE, right = (closed == "right"), ...)
 }
 
-# Find the left side of left-most bin
-find_origin <- function(x_range, width, boundary) {
-  shift <- floor((x_range[1] - boundary) / width)
-  boundary + shift * width
-}
-
 breaks <- function(x, equal, nbins = NULL, binwidth = NULL) {
   equal <- arg_match0(equal, c("numbers", "width"))
   if ((!is.null(nbins) && !is.null(binwidth)) || (is.null(nbins) && is.null(binwidth))) {
diff --git a/R/utilities-matrix.R b/R/utilities-matrix.R
deleted file mode 100644
index dd35e082ba..0000000000
--- a/R/utilities-matrix.R
+++ /dev/null
@@ -1,25 +0,0 @@
-# Col union
-# Form the union of columns in a and b.  If there are columns of the same name in both a and b, take the column from a.
-#
-# @param data frame a
-# @param data frame b
-# @keyword internal
-cunion <- function(a, b) {
-  if (length(a) == 0) return(b)
-  if (length(b) == 0) return(a)
-
-  cbind(a, b[setdiff(names(b), names(a))])
-}
-
-# Interleave (or zip) multiple units into one vector
-interleave <- function(...) UseMethod("interleave")
-#' @export
-interleave.unit <- function(...) {
-  units <- lapply(list(...), as.list)
-  interleaved_list <- interleave.default(!!!units)
-  inject(unit.c(!!!interleaved_list))
-}
-#' @export
-interleave.default <- function(...) {
-  vec_interleave(...)
-}
diff --git a/R/utilities.R b/R/utilities.R
index 56325e83d9..8772ed771b 100644
--- a/R/utilities.R
+++ b/R/utilities.R
@@ -84,16 +84,6 @@ clist <- function(l) {
   paste(paste(names(l), l, sep = " = ", collapse = ", "), sep = "")
 }
 
-# Return unique columns
-# This is used for figuring out which columns are constant within a group
-#
-# @keyword internal
-uniquecols <- function(df) {
-  df <- df[1, sapply(df, is_unique), drop = FALSE]
-  rownames(df) <- seq_len(nrow(df))
-  df
-}
-
 #' Convenience function to remove missing values from a data.frame
 #'
 #' Remove all non-complete rows, with a warning if `na.rm = FALSE`.
@@ -200,12 +190,6 @@ waiver <- function() structure(list(), class = "waiver")
 
 is.waive <- function(x) inherits(x, "waiver")
 
-
-rescale01 <- function(x) {
-  rng <- range(x, na.rm = TRUE)
-  (x - rng[1]) / (rng[2] - rng[1])
-}
-
 pal_binned <- function(palette) {
   function(x) {
     palette(length(x))
@@ -247,15 +231,6 @@ gg_dep <- function(version, msg) {
   invisible()
 }
 
-has_name <- function(x) {
-  nms <- names(x)
-  if (is.null(nms)) {
-    return(rep(FALSE, length(x)))
-  }
-
-  !is.na(nms) & nms != ""
-}
-
 # Use chartr() for safety since toupper() fails to convert i to I in Turkish locale
 lower_ascii <- "abcdefghijklmnopqrstuvwxyz"
 upper_ascii <- "ABCDEFGHIJKLMNOPQRSTUVWXYZ"
@@ -273,7 +248,9 @@ toupper <- function(x) {
 # Convert a snake_case string to camelCase
 camelize <- function(x, first = FALSE) {
   x <- gsub("_(.)", "\\U\\1", x, perl = TRUE)
-  if (first) x <- firstUpper(x)
+  if (first) {
+    x <- paste0(to_upper_ascii(substring(x, 1, 1)), substring(x, 2))
+  }
   x
 }
 
@@ -284,10 +261,6 @@ snakeize <- function(x) {
   to_lower_ascii(x)
 }
 
-firstUpper <- function(s) {
-  paste0(to_upper_ascii(substring(s, 1, 1)), substring(s, 2))
-}
-
 snake_class <- function(x) {
   snakeize(class(x)[1])
 }
@@ -320,15 +293,6 @@ compact <- function(x) {
 
 is.formula <- function(x) inherits(x, "formula")
 
-deparse2 <- function(x) {
-  y <- deparse(x, backtick = TRUE)
-  if (length(y) == 1) {
-    y
-  } else {
-    paste0(y[[1]], "...")
-  }
-}
-
 dispatch_args <- function(f, ...) {
   args <- list(...)
   formals <- formals(f)
@@ -337,7 +301,6 @@ dispatch_args <- function(f, ...) {
   f
 }
 
-is_missing_arg <- function(x) identical(x, quote(expr = ))
 # Get all arguments in a function as a list. Will fail if an ellipsis argument
 # named .ignore
 # @param ... passed on in case enclosing function uses ellipsis in argument list
@@ -346,7 +309,8 @@ find_args <- function(...) {
   args <- names(formals(sys.function(sys.parent(1))))
 
   vals <- mget(args, envir = env)
-  vals <- vals[!vapply(vals, is_missing_arg, logical(1))]
+  # Remove missing arguments
+  vals <- vals[!vapply(vals, identical, logical(1), y = quote(expr = ))]
 
   modify_list(vals, dots_list(..., `...` = NULL, .ignore_empty = "all"))
 }
@@ -363,14 +327,6 @@ with_seed_null <- function(seed, code) {
   }
 }
 
-seq_asc <- function(to, from) {
-  if (to > from) {
-    integer()
-  } else {
-    to:from
-  }
-}
-
 # Wrapping vctrs data_frame constructor with no name repair
 data_frame0 <- function(...) data_frame(..., .name_repair = "minimal")
 
@@ -380,23 +336,19 @@ unique0 <- function(x, ...) if (is.null(x)) x else vec_unique(x, ...)
 # Code readability checking for uniqueness
 is_unique <- function(x) vec_unique_count(x) == 1L
 
-is_scalar_numeric <- function(x) is_bare_numeric(x, n = 1L)
-
 # Check inputs with tibble but allow column vectors (see #2609 and #2374)
 as_gg_data_frame <- function(x) {
-  x <- lapply(x, validate_column_vec)
+  x <- lapply(x, drop_column_vec)
   data_frame0(!!!x)
 }
-validate_column_vec <- function(x) {
-  if (is_column_vec(x)) {
+
+drop_column_vec <- function(x) {
+  dims <- dim(x)
+  if (length(dims) == 2L && dims[[2]] == 1L) {
     dim(x) <- NULL
   }
   x
 }
-is_column_vec <- function(x) {
-  dims <- dim(x)
-  length(dims) == 2L && dims[[2]] == 1L
-}
 
 # Parse takes a vector of n lines and returns m expressions.
 # See https://github.com/tidyverse/ggplot2/issues/2864 for discussion.
@@ -686,24 +638,6 @@ is_bang <- function(x) {
   })
 }
 
-is_triple_bang <- function(x) {
-  if (!is_bang(x)) {
-    return(FALSE)
-  }
-
-  x <- x[[2]]
-  if (!is_bang(x)) {
-    return(FALSE)
-  }
-
-  x <- x[[2]]
-  if (!is_bang(x)) {
-    return(FALSE)
-  }
-
-  TRUE
-}
-
 # Restart handler for using vec_rbind with mix of types
 # Ordered is coerced to factor
 # If a character vector is present the other is converted to character
diff --git a/man/ggproto.Rd b/man/ggproto.Rd
index c00c2000f6..11e3af8093 100644
--- a/man/ggproto.Rd
+++ b/man/ggproto.Rd
@@ -3,14 +3,11 @@
 \name{ggproto}
 \alias{ggproto}
 \alias{ggproto_parent}
-\alias{is.ggproto}
 \title{Create a new ggproto object}
 \usage{
 ggproto(`_class` = NULL, `_inherit` = NULL, ...)
 
 ggproto_parent(parent, self)
-
-is.ggproto(x)
 }
 \arguments{
 \item{_class}{Class name to assign to the object. This is stored as the class
@@ -24,8 +21,6 @@ inherit from any object.}
 functions that become methods of the class or regular objects.}
 
 \item{parent, self}{Access parent class \code{parent} of object \code{self}.}
-
-\item{x}{An object to test.}
 }
 \description{
 Construct a new object with \code{ggproto()}, test with \code{is.ggproto()},
diff --git a/man/is.Coord.Rd b/man/is.Coord.Rd
deleted file mode 100644
index 50b4520640..0000000000
--- a/man/is.Coord.Rd
+++ /dev/null
@@ -1,12 +0,0 @@
-% Generated by roxygen2: do not edit by hand
-% Please edit documentation in R/coord-.R
-\name{is.Coord}
-\alias{is.Coord}
-\title{Is this object a coordinate system?}
-\usage{
-is.Coord(x)
-}
-\description{
-Is this object a coordinate system?
-}
-\keyword{internal}
diff --git a/man/is.facet.Rd b/man/is.facet.Rd
deleted file mode 100644
index bd8fc7b5ba..0000000000
--- a/man/is.facet.Rd
+++ /dev/null
@@ -1,15 +0,0 @@
-% Generated by roxygen2: do not edit by hand
-% Please edit documentation in R/facet-.R
-\name{is.facet}
-\alias{is.facet}
-\title{Is this object a faceting specification?}
-\usage{
-is.facet(x)
-}
-\arguments{
-\item{x}{object to test}
-}
-\description{
-Is this object a faceting specification?
-}
-\keyword{internal}
diff --git a/man/is.ggplot.Rd b/man/is.ggplot.Rd
deleted file mode 100644
index 837bc9a919..0000000000
--- a/man/is.ggplot.Rd
+++ /dev/null
@@ -1,15 +0,0 @@
-% Generated by roxygen2: do not edit by hand
-% Please edit documentation in R/plot.R
-\name{is.ggplot}
-\alias{is.ggplot}
-\title{Reports whether x is a ggplot object}
-\usage{
-is.ggplot(x)
-}
-\arguments{
-\item{x}{An object to test}
-}
-\description{
-Reports whether x is a ggplot object
-}
-\keyword{internal}
diff --git a/man/is.theme.Rd b/man/is.theme.Rd
deleted file mode 100644
index c7930a2e96..0000000000
--- a/man/is.theme.Rd
+++ /dev/null
@@ -1,15 +0,0 @@
-% Generated by roxygen2: do not edit by hand
-% Please edit documentation in R/theme.R
-\name{is.theme}
-\alias{is.theme}
-\title{Reports whether x is a theme object}
-\usage{
-is.theme(x)
-}
-\arguments{
-\item{x}{An object to test}
-}
-\description{
-Reports whether x is a theme object
-}
-\keyword{internal}
diff --git a/man/is_tests.Rd b/man/is_tests.Rd
new file mode 100644
index 0000000000..62ded3db09
--- /dev/null
+++ b/man/is_tests.Rd
@@ -0,0 +1,63 @@
+% Generated by roxygen2: do not edit by hand
+% Please edit documentation in R/ggproto.R, R/aes.R, R/geom-.R, R/coord-.R,
+%   R/facet-.R, R/stat-.R, R/theme-elements.R, R/guide-.R, R/layer.R,
+%   R/guides-.R, R/margins.R, R/plot.R, R/position-.R, R/scale-.R, R/theme.R
+\name{is.ggproto}
+\alias{is.ggproto}
+\alias{is.mapping}
+\alias{is.geom}
+\alias{is.coord}
+\alias{is.Coord}
+\alias{is.facet}
+\alias{is.stat}
+\alias{is.element}
+\alias{is.guide}
+\alias{is.layer}
+\alias{is.guides}
+\alias{is.margin}
+\alias{is_tests}
+\alias{is.ggplot}
+\alias{is.position}
+\alias{is.scale}
+\alias{is.theme}
+\title{Reports whether x is a type of object}
+\usage{
+is.ggproto(x)
+
+is.mapping(x)
+
+is.geom(x)
+
+is.coord(x)
+
+is.Coord(x) # Deprecated
+
+is.facet(x)
+
+is.stat(x)
+
+is.element(x)
+
+is.guide(x)
+
+is.layer(x)
+
+is.guides(x)
+
+is.margin(x)
+
+is.ggplot(x)
+
+is.position(x)
+
+is.scale(x)
+
+is.theme(x)
+}
+\arguments{
+\item{x}{An object to test}
+}
+\description{
+Reports whether x is a type of object
+}
+\keyword{internal}
diff --git a/tests/testthat/_snaps/compat-plyr.md b/tests/testthat/_snaps/compat-plyr.md
deleted file mode 100644
index d31d586cc8..0000000000
--- a/tests/testthat/_snaps/compat-plyr.md
+++ /dev/null
@@ -1,16 +0,0 @@
-# input checks work in compat functions
-
-    Can only remove rownames from <data.frame> and <matrix> objects.
-
----
-
-    `x` must be a factor or character vector, not an integer vector.
-
----
-
-    Must be a character vector, call, or formula.
-
----
-
-    `x` must be a <numeric> vector, not a character vector.
-
diff --git a/tests/testthat/_snaps/margins.md b/tests/testthat/_snaps/margins.md
deleted file mode 100644
index 3eefe771b7..0000000000
--- a/tests/testthat/_snaps/margins.md
+++ /dev/null
@@ -1,4 +0,0 @@
-# justify_grobs() checks input
-
-    `grobs` must be an individual <grob> or list of <grob> objects, not the number 1.
-
diff --git a/tests/testthat/_snaps/utilities.md b/tests/testthat/_snaps/utilities.md
index 4560379f1e..37138df4e9 100644
--- a/tests/testthat/_snaps/utilities.md
+++ b/tests/testthat/_snaps/utilities.md
@@ -50,10 +50,6 @@
 
     Only one of `boundary` and `center` may be specified.
 
-# interleave() checks the vector lengths
-
-    Can't recycle `..1` (size 4) to match `..2` (size 0).
-
 # summary method gives a nice summary
 
     Code
diff --git a/tests/testthat/test-compat-plyr.R b/tests/testthat/test-compat-plyr.R
deleted file mode 100644
index b8fd891ebf..0000000000
--- a/tests/testthat/test-compat-plyr.R
+++ /dev/null
@@ -1,6 +0,0 @@
-test_that("input checks work in compat functions", {
-  expect_snapshot_error(unrowname(1:6))
-  expect_snapshot_error(revalue(1:7, c("5" = 2)))
-  expect_snapshot_error(as.quoted(1:7))
-  expect_snapshot_error(round_any(letters))
-})
diff --git a/tests/testthat/test-facet-.R b/tests/testthat/test-facet-.R
index 9e536798a8..5084737622 100644
--- a/tests/testthat/test-facet-.R
+++ b/tests/testthat/test-facet-.R
@@ -21,7 +21,7 @@ test_that("as_facets_list() coerces character vectors", {
 
   expect_identical(as_facets_list("foo"), list(foobar[1]))
   expect_identical(as_facets_list(c("foo", "bar")), list(foobar[1], foobar[2]))
-  expect_identical(wrap_as_facets_list(c("foo", "bar")), foobar)
+  expect_identical(compact_facets(c("foo", "bar")), foobar)
 })
 
 test_that("as_facets_list() coerces lists", {
@@ -47,12 +47,12 @@ test_that("facets reject aes()", {
   expect_error(facet_grid(aes(foo)), "Please use `vars()` to supply facet variables", fixed = TRUE)
 })
 
-test_that("wrap_as_facets_list() returns a quosures object with compacted", {
-  expect_identical(wrap_as_facets_list(vars(foo)), quos(foo = foo))
-  expect_identical(wrap_as_facets_list(~foo + bar), quos(foo = foo, bar = bar))
+test_that("compact_facets() returns a quosures object with compacted", {
+  expect_identical(compact_facets(vars(foo)), quos(foo = foo))
+  expect_identical(compact_facets(~foo + bar), quos(foo = foo, bar = bar))
 
   f <- function(x) {
-    expect_identical(wrap_as_facets_list(vars(foo, {{ x }}, bar)), quos(foo = foo, bar = bar))
+    expect_identical(compact_facets(vars(foo, {{ x }}, bar)), quos(foo = foo, bar = bar))
   }
 
   f(NULL)
@@ -71,12 +71,12 @@ test_that("grid_as_facets_list() returns a list of quosures objects with compact
   f()
 })
 
-test_that("wrap_as_facets_list() and grid_as_facets_list() accept empty specs", {
-  expect_identical(wrap_as_facets_list(NULL), quos())
-  expect_identical(wrap_as_facets_list(list()), quos())
-  expect_identical(wrap_as_facets_list(. ~ .), quos())
-  expect_identical(wrap_as_facets_list(list(. ~ .)), quos())
-  expect_identical(wrap_as_facets_list(list(NULL)), quos())
+test_that("compact_facets() and grid_as_facets_list() accept empty specs", {
+  expect_identical(compact_facets(NULL), quos())
+  expect_identical(compact_facets(list()), quos())
+  expect_identical(compact_facets(. ~ .), quos())
+  expect_identical(compact_facets(list(. ~ .)), quos())
+  expect_identical(compact_facets(list(NULL)), quos())
 
   expect_identical(grid_as_facets_list(list(), NULL), list(rows = quos(), cols = quos()))
   expect_identical(grid_as_facets_list(. ~ ., NULL), list(rows = quos(), cols = quos()))
diff --git a/tests/testthat/test-margins.R b/tests/testthat/test-margins.R
deleted file mode 100644
index 522c457445..0000000000
--- a/tests/testthat/test-margins.R
+++ /dev/null
@@ -1,3 +0,0 @@
-test_that("justify_grobs() checks input", {
-  expect_snapshot_error(justify_grobs(1))
-})
diff --git a/tests/testthat/test-stat-bin2d.R b/tests/testthat/test-stat-bin2d.R
index 31e9c819c6..54d95679c9 100644
--- a/tests/testthat/test-stat-bin2d.R
+++ b/tests/testthat/test-stat-bin2d.R
@@ -32,8 +32,8 @@ test_that("breaks override binwidth", {
     )
 
   out <- get_layer_data(base)
-  expect_equal(out$xbin, cut(df$x, adjust_breaks(integer_breaks), include.lowest = TRUE, labels = FALSE))
-  expect_equal(out$ybin, cut(df$y, adjust_breaks(half_breaks), include.lowest = TRUE, labels = FALSE))
+  expect_equal(out$xbin, cut(df$x, bins(integer_breaks)$fuzzy, include.lowest = TRUE, labels = FALSE))
+  expect_equal(out$ybin, cut(df$y, bins(half_breaks)$fuzzy, include.lowest = TRUE, labels = FALSE))
 })
 
 test_that("breaks are transformed by the scale", {
diff --git a/tests/testthat/test-utilities.R b/tests/testthat/test-utilities.R
index 315ca88ebc..a602eb22c7 100644
--- a/tests/testthat/test-utilities.R
+++ b/tests/testthat/test-utilities.R
@@ -132,10 +132,6 @@ test_that("cut_*() checks its input and output", {
   expect_snapshot_error(cut_width(1:10, 1, center = 0, boundary = 0.5))
 })
 
-test_that("interleave() checks the vector lengths", {
-  expect_snapshot_error(interleave(1:4, numeric()))
-})
-
 test_that("vec_rbind0 can combined ordered factors", {
 
   withr::local_options(lifecycle_verbosity = "warning")