Explication of lazy warnings

Lazy warning are to be used for +, ~ and ? conversions, as well as
for the ??? stub.

Author: TimToady

S02-bits.pod

@@ -14,7 +14,7 @@ Synopsis 2: Bits and Pieces
     Created: 10 Aug 2004
 
     Last Modified: 28 Jul 2012
-    Version: 267
+    Version: 268
 
 This document summarizes Apocalypse 2, which covers small-scale
 lexical items and typological issues.  (These Synopses also contain
@@ -2264,8 +2264,9 @@ Since method calls are performed directly on any object, C<Nil>
 can respond to certain method calls.  C<Nil.defined> returns
 C<False> (whereas C<().defined> returns C<True>).  C<Nil.so> also
 returns C<False>.  C<Nil.ACCEPTS> matches only a C<Nil> value.  C<Nil.perl> and
-C<Nil.gist> return C<'Nil'>.  C<Nil.Stringy> and C<Nil.Str> return '' with a warning.
-C<Nil.Numeric> returns 0 with a warning.  Any undefined method call
+C<Nil.gist> return C<'Nil'>.  C<Nil.Stringy> and C<Nil.Str> fail with a resumable warning
+that returns a value of C<''> on resumption.  C<Nil.Numeric> likewise fails
+with resumable warning that returns 0 on resumption.  Any undefined method call
 on C<Nil> returns C<Nil>, so that C<Nil> propagates down method
 call chains.
 

S04-control.pod

@@ -14,7 +14,7 @@ Synopsis 4: Blocks and Statements
     Created: 19 Aug 2004
 
     Last Modified: 28 Jul 2012
-    Version: 117
+    Version: 118
 
 This document summarizes Apocalypse 4, which covers the block and
 statement syntax of Perl.
@@ -1216,6 +1216,15 @@ separate from the catch lambda, though an implementation is allowed
 to combine them if it is careful to retain separate semantics for
 catch and control exceptions.
 
+One additional level of control is the notion of I<lazy warnings>.
+If, instead of throwing a warning directly, the program calls C<fail()>
+with a resumable exception, the throwing of the warning is delayed
+until first use (or the caller's policy) requires it to be thrown.
+If the warning exception supports the C<.resume_value> method, that
+will be the value of the failure after it has resumed.  Otherwise the
+value will be the null string.  The C<+>, C<~>, and C<?> coercions
+use these lazy warnings to allow (but not require) failsoft semantics.
+
 =head1 The goto statement
 X<goto>
 

S06-routines.pod

@@ -16,8 +16,8 @@ Synopsis 6: Subroutines
 
     Created: 21 Mar 2003
 
-    Last Modified: 23 Jan 2012
-    Version: 154
+    Last Modified: 28 Jul 2012
+    Version: 155
 
 This document summarizes Apocalypse 6, which covers subroutines and the
 new type system.
@@ -448,7 +448,8 @@ you must explicitly use the "C<supersede>" declarator.  (The compiler may
 refuse to do this if it has already committed to the previous definition.)
 
 The C<...> is the "yadayadayada" operator, which is executable but
-returns a failure.  You can also use C<???> to produce a warning,
+returns a failure.  You can also use C<???> to fail with a warning
+(a lazy one, to be issued only if the the value is actually used),
 or C<!!!> to always die.  These also officially define stub blocks.
 Any of these yada operators will be taken as a stub if used as the main
 operator of the first statement in the block.  (Statement modifiers