FEAT: allowed to make block! using pair!

resolves: Oldes/Rebol-wishes#26

Author: Oldes

src/core/t-block.c

@@ -353,6 +353,13 @@ static void No_Nones_Or_Logic(REBVAL *arg) {
 		goto done;
 	}
 
+	// use `make block! pair!` for block preallocation
+	if (IS_PAIR(arg)) {
+		len = (REBCNT)MAX(1, VAL_PAIR_X_INT(arg)) * (REBCNT)MAX(1, VAL_PAIR_Y_INT(arg));
+		Set_Series(type, value, Make_Block(len));
+		return;
+	}
+
 	// else not supported make block! ...
 	Trap_Arg(arg);
 

src/tests/units/make-test.r3

@@ -227,7 +227,9 @@ Rebol [
 		--assert  error?  try [make block! quote 4%         ] ; percent!
 		--assert  error?  try [make block! quote $4         ] ; money!
 		--assert  error?  try [make block! quote #"a"       ] ; char!
-		--assert  error?  try [make block! quote 2x2        ] ; pair!
+		--assert  []    = try [make block! quote 2x2        ] ; pair! - preallocated for at least 4 values
+		--assert  []    = try [make block! quote 0x2.2      ] ; pair! - preallocated for at least 2 values (1*2)
+		--assert  []    = try [make block! quote 2x-2       ] ; pair! - preallocated for at least 2 values (2*1)
 		--assert  error?  try [make block! quote 1.1.1      ] ; tuple!
 		--assert  error?  try [make block! quote 10:00      ] ; time!
 		--assert  error?  try [make block! quote 2000-01-01 ] ; date!