Make 'my %h is Set(|Hash) = ...;' DWIM

- in response to RT #132352 and RT #132353
- make also sure we can initialize Sets only once

src/core/Set.pm

@@ -11,6 +11,21 @@ my class Set does Setty {
           set()
         )
     }
+    method STORE(*@pairs --> Set:D) {
+        nqp::if(
+          (my $iterator := @pairs.iterator).is-lazy,
+          Failure.new(X::Cannot::Lazy.new(:action<initialize>,:what(self.^name))),
+          nqp::if(
+            $!elems || nqp::eqaddr(self,set()),
+            X::Immutable.new( method => 'STORE', typename => self.^name ).throw,
+            self.SET-SELF(
+              Rakudo::QuantHash.ADD-PAIRS-TO-SET(
+                nqp::create(Rakudo::Internals::IterationSet), $iterator
+              )
+            )
+          )
+        )
+    }
     multi method new(Set:_:) {
         nqp::if(
           nqp::eqaddr(self.WHAT,Set),

src/core/SetHash.pm

@@ -10,6 +10,21 @@ my class SetHash does Setty {
         )
     }
 
+    method STORE(*@pairs --> SetHash:D) {
+        nqp::if(
+          (my $iterator := @pairs.iterator).is-lazy,
+          Failure.new(X::Cannot::Lazy.new(:action<initialize>,:what(self.^name))),
+          nqp::stmts(
+            nqp::bindattr(self,::?CLASS,'$!elems',
+              Rakudo::QuantHash.ADD-PAIRS-TO-SET(
+                nqp::create(Rakudo::Internals::IterationSet), $iterator
+              )
+            ),
+            self
+          )
+        )
+    }
+
 #--- selector methods
 
     multi method grab(SetHash:D:) {