Add type restrictions to process

src/process.cr

@@ -17,7 +17,7 @@ class Process
   # not run any handlers registered with `at_exit`, use `::exit` for that.
   #
   # *status* is the exit status of the current process.
-  def self.exit(status = 0) : NoReturn
+  def self.exit(status : Int32 = 0) : NoReturn
     Crystal::System::Process.exit(status)
   end
 
@@ -285,7 +285,7 @@ class Process
     fork_error.close unless fork_error.in?(error, STDERR)
   end
 
-  def finalize
+  def finalize : Nil
     @process_info.release
   end
 
@@ -515,7 +515,7 @@ end
 # ```
 #
 # See [`Command` literals](https://crystal-lang.org/reference/syntax_and_semantics/literals/command.html) in the language reference.
-def `(command) : String
+def `(command : String) : String
   process = Process.new(command, shell: true, input: Process::Redirect::Inherit, output: Process::Redirect::Pipe, error: Process::Redirect::Inherit)
   output = process.output.gets_to_end
   status = process.wait

src/process/status.cr

@@ -95,7 +95,7 @@ enum Process::ExitReason
   # Returns `true` if the process exited abnormally.
   #
   # This includes all values except `Normal`.
-  def abnormal?
+  def abnormal? : Bool
     !normal?
   end
 
@@ -107,7 +107,7 @@ enum Process::ExitReason
   # ```
   #
   # `Status#description` provides more detail for a specific process status.
-  def description
+  def description : String
     case self
     in .normal?
       "Process exited normally"
@@ -413,7 +413,7 @@ class Process::Status
   # ```
   #
   # `ExitReason#description` provides the specific messages for non-signal exits.
-  def description
+  def description : String
     if exit_reason.signal? && (signal = exit_signal?)
       "Process received and didn't handle signal #{signal}"
     else