Require tuple before env in the prelude (#8771)

spec/compiler/codegen/cast_spec.cr

@@ -497,4 +497,15 @@ describe "Code gen: cast" do
       Base.as(Base | Base.class).as?(Base | Impl).nil?
       CRYSTAL
   end
+
+  it "casts same-type tuple to Enumerable whose splat collapses (#8771)" do
+    # `Tuple(String, String)` is instantiated early (via `ENV`) before
+    # `Tuple` includes `Indexable`, so it used to be missing from
+    # `Enumerable(String).including_types`, crashing this upcast.
+    run(<<-CRYSTAL).to_string.should eq("ab")
+      require "prelude"
+
+      ({"a", "b"}.as(Enumerable(String))).to_a.join
+      CRYSTAL
+  end
 end

src/prelude.cr

@@ -18,6 +18,13 @@ require "iterable"
 require "iterator"
 require "steppable"
 require "indexable"
+# `Tuple` includes `Indexable(Union(*T))`. It must be required here, before any
+# file that can register a tuple as an including type of a module (e.g. `env`'s
+# `extend Enumerable(...)`), otherwise that early instantiation runs with an
+# incomplete parent list and is missing from the module's including types,
+# breaking `as Enumerable(T)` upcasts (#8771).
+require "tuple"
+require "named_tuple"
 require "string"
 require "number"
 require "primitives"
@@ -53,7 +60,6 @@ require "io"
 require "kernel"
 require "math/math"
 require "mutex"
-require "named_tuple"
 require "nil"
 require "humanize"
 require "path"
@@ -78,7 +84,6 @@ require "symbol"
 require "system"
 require "crystal/system/thread"
 require "time"
-require "tuple"
 require "unicode"
 require "union"
 require "va_list"