Move almost all view functions on best::vec and best::strbuf behi…

…nd `operator->` (#25)

This patch introduces `best::arrow<T>`, a helper for returning anything
out of an `operator->`. The doc comment on the type explains why it
exists and what C++ semantics it abuses.

`best::vec` and `best::strbuf` now have `operator->`s that effectively
return `best::span` and `best::str`, respectively. This allows the
removal of a ton of duplicated functions, and means that the owned types
can't "lag" behind the unowned types! This also means that e.g.
`best::box<T[]>` does not need to duplicate all of the functions from
`best::span`, like to `best::vec` used to.

best/base/fwd.h

@@ -72,6 +72,10 @@ class pun;
 // template <typename, best::option<size_t>>
 // class span;
 
+// best/func/arrow.h
+template <typename>
+class arrow;
+
 // best/func/fnref.h
 template <typename>
 class fnref;

best/cli/parser.cc

@@ -135,8 +135,8 @@ void normalize(best::strbuf& name, const auto& about) {
   }
 
   // TODO: also check the ends.
-  if (name.starts_with('-') || name.starts_with('_') ||
-      name.contains(&reserved_rune)) {
+  if (name->starts_with('-') || name->starts_with('_') ||
+      name->contains(&reserved_rune)) {
     best::wtf("field {}::{}'s name ({:?}) contains reserved runes",
               about.strukt->path(), about.field, name);
   }
@@ -342,8 +342,8 @@ void cli::init() {
   });
 
   // Now, sort the flags so we can bisect through them later.
-  impl_->sorted_flags.sort(&impl::entry::key);
-  impl_->sorted_subs.sort(&impl::entry::key);
+  impl_->sorted_flags->sort(&impl::entry::key);
+  impl_->sorted_subs->sort(&impl::entry::key);
 
   // Check for duplicates.
   best::option<best::str> prev;
@@ -647,7 +647,7 @@ best::strbuf cli::usage(best::pretext<wtf8> exe, bool hidden) const {
 
   best::format(out, "Usage: {}", exe);
   if (!parents.is_empty()) {
-    parents.reverse();
+    parents->reverse();
     for (auto sub : parents) {
       best::format(out, " {}", sub);
     }
@@ -809,7 +809,7 @@ best::strbuf cli::usage(best::pretext<wtf8> exe, bool hidden) const {
     }
 
     best::str prefix = e.key[{
-        .end = e.key.size() - e.key.split('.').last()->size(),
+        .end = e.key.size() - e.key->split('.').last()->size(),
     }];
     // Chop off everything past the last `.` to make the prefix.
 

best/container/BUILD

@@ -169,6 +169,7 @@ cc_library(
     ":object",
     ":option",
     ":span",
+    "//best/func:arrow",
     "//best/math:bit",
     "//best/math:overflow",
     "//best/memory:allocator",

best/container/span_test.cc

@@ -237,10 +237,10 @@ best::test FrontAndBack = [](auto& t) {
 
 best::test Swap = [](auto& t) {
   best::vec<int> ints = {1, 2, 3, 4, 5};
-  ints.as_span().swap(1, 2);
+  ints->swap(1, 2);
   t.expect_eq(ints, best::span{1, 3, 2, 4, 5});
 
-  ints.as_span().reverse();
+  ints->reverse();
   t.expect_eq(ints, best::span{5, 4, 2, 3, 1});
 };
 
@@ -332,13 +332,13 @@ best::test Sort = [](auto& t) {
   best::mark_sort_header_used();
 
   best::vec<int> ints = {5, 4, 3, 2, 1};
-  ints.as_span().sort();
+  ints->sort();
   t.expect_eq(ints, best::span{1, 2, 3, 4, 5});
 
-  ints.as_span().stable_sort([](int x) { return best::count_ones(x); });
+  ints->stable_sort([](int x) { return best::count_ones(x); });
   t.expect_eq(ints, best::span{1, 2, 4, 3, 5});
 
-  ints.as_span().sort([](int x, int y) { return y <=> x; });
+  ints->sort([](int x, int y) { return y <=> x; });
   t.expect_eq(ints, best::span{5, 4, 3, 2, 1});
 };