Tighten stdlib typespecs to match implementations

Candidates found by cross-checking @specs against the type signatures
inferred by the compiler (see #15559): these specs declared strictly
wider return types than the functions can produce, where the gap
carries no intentional API room (deliberately abstract contracts, such
as atom() covering future values, are left untouched):

  * File.Stream.t/0: type the struct fields (mirrors IO.Stream.t/0)
  * Map.new/0: %{} instead of map()
  * Logger.levels/0: :logger.level() excludes :warn, which is only an
    accepted input alias and is never returned
  * Macro.Env.location/1 and Macro.Env.stacktrace/1: precise shapes

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

Author: lukaszsamson

lib/elixir/lib/file/stream.ex

@@ -18,7 +18,13 @@ defmodule File.Stream do
 
   defstruct path: nil, modes: [], line_or_bytes: :line, raw: true, node: nil
 
-  @type t :: %__MODULE__{}
+  @type t :: %__MODULE__{
+          path: Path.t(),
+          modes: [term()],
+          line_or_bytes: :line | pos_integer(),
+          raw: boolean(),
+          node: node()
+        }
 
   @doc false
   def __build__(path, line_or_bytes, modes) do

lib/elixir/lib/macro/env.ex

@@ -203,7 +203,7 @@ defmodule Macro.Env do
   Returns a keyword list containing the file and line
   information as keys.
   """
-  @spec location(t) :: keyword
+  @spec location(t) :: [file: file, line: line]
   def location(env)
 
   def location(%{__struct__: Macro.Env, file: file, line: line}) do
@@ -700,7 +700,7 @@ defmodule Macro.Env do
   @doc """
   Returns the environment stacktrace.
   """
-  @spec stacktrace(t) :: list
+  @spec stacktrace(t) :: [{module, atom, arity, keyword}]
   def stacktrace(%{__struct__: Macro.Env} = env) do
     cond do
       is_nil(env.module) ->

lib/elixir/lib/map.ex

@@ -201,7 +201,7 @@ defmodule Map do
       %{}
 
   """
-  @spec new :: map
+  @spec new :: %{}
   def new, do: %{}
 
   @doc """

lib/elixir/lib/module.ex

@@ -754,7 +754,7 @@ defmodule Module do
 
   """
   @doc since: "1.12.0"
-  @spec reserved_attributes() :: map
+  @spec reserved_attributes() :: %{optional(atom()) => %{doc: binary()}}
   def reserved_attributes() do
     %{
       after_compile: %{

lib/logger/lib/logger.ex

@@ -537,7 +537,7 @@ defmodule Logger do
   Returns all the available levels.
   """
   @doc since: "1.16.0"
-  @spec levels() :: [level(), ...]
+  @spec levels() :: [:logger.level(), ...]
   def levels(), do: @levels
 
   @doc ~S"""