Split parameter-driven return types into overloads

core/kernel.rbs

@@ -2233,7 +2233,8 @@ module Kernel : BasicObject
   #
   # Raises an exception if the new process could not execute.
   #
-  def self?.system: (String command, *String args, ?unsetenv_others: bool, ?pgroup: true | Integer, ?umask: Integer, ?in: redirect_fd, ?out: redirect_fd, ?err: redirect_fd, ?close_others: bool, ?chdir: String, ?exception: bool) -> (NilClass | FalseClass | TrueClass)
+  def self?.system: (String command, *String args, ?unsetenv_others: bool, ?pgroup: true | Integer, ?umask: Integer, ?in: redirect_fd, ?out: redirect_fd, ?err: redirect_fd, ?close_others: bool, ?chdir: String, ?exception: false) -> (NilClass | FalseClass | TrueClass)
+                  | (String command, *String args, ?unsetenv_others: bool, ?pgroup: true | Integer, ?umask: Integer, ?in: redirect_fd, ?out: redirect_fd, ?err: redirect_fd, ?close_others: bool, ?chdir: String, exception: true) -> TrueClass
                   | (Hash[string, string?] env, String command, *String args, ?unsetenv_others: bool, ?pgroup: true | Integer, ?umask: Integer, ?in: redirect_fd, ?out: redirect_fd, ?err: redirect_fd, ?close_others: bool, ?chdir: String, ?exception: bool) -> (NilClass | FalseClass | TrueClass)
 
   # An interface used with `trace_var` (and `untrace_var`) for custom command types.

core/thread.rbs

@@ -1719,7 +1719,8 @@ class Thread::Queue[E = untyped] < Object
   # If `timeout` seconds have passed and no data is available `nil` is returned.
   # If `timeout` is `0` it returns immediately.
   #
-  def pop: (?boolish non_block, ?timeout: _ToF?) -> E?
+  def pop: (?false non_block, ?timeout: _ToF?) -> E?
+         | (true non_block) -> E
 
   # <!--
   #   rdoc-file=thread_sync.c

stdlib/bigdecimal/0/big_decimal.rbs

@@ -1238,7 +1238,8 @@ module Kernel
   # Raises an exception if `value` evaluates to a Float and `digits` is larger
   # than Float::DIG + 1.
   #
-  def self?.BigDecimal: (real | string | BigDecimal initial, ?int digits, ?exception: bool) -> BigDecimal
+  def self?.BigDecimal: (real | string | BigDecimal initial, ?int digits, ?exception: true) -> BigDecimal
+                      | (real | string | BigDecimal initial, ?int digits, exception: false) -> BigDecimal?
 end
 
 %a{annotate:rdoc:skip}