CHANGE: have % to be a valid word and not an empty file

related to: Oldes/Rebol-issues#2450

src/core/l-scan.c

@@ -874,7 +874,13 @@
         case LEX_SPECIAL_AT:            /* @username */
             return TOKEN_REF;
 
-        case LEX_SPECIAL_PERCENT:       /* %filename */
+        case LEX_SPECIAL_PERCENT:
+			if (IS_LEX_DELIMIT(cp[1]) && cp[1] != '"' && cp[1] != '/') {
+				return TOKEN_WORD; // special case for having % as a word (reminder op!)
+			} else if (cp[1] == ':' && IS_LEX_DELIMIT(cp[2])) {
+				return TOKEN_SET;
+			}
+			/* %filename */
             cp = scan_state->end;
             if (*cp == '"') {
 				cp = Scan_Quote(cp, scan_state);  // stores result string in BUF_MOLD
@@ -901,6 +907,13 @@
 				scan_state->end = cp+1;
 				return TOKEN_GET;
 			}
+			if (cp[1] == '%' && IS_LEX_DELIMIT(cp[2])) {
+				if (cp[2] == '"' || cp[2] == '/') { // no :%"" or :%/
+					scan_state->end = cp + 3;
+					return -TOKEN_GET;
+				}
+				return TOKEN_GET; // allowed :%
+			}
             type = TOKEN_GET;
             cp++;                       /* skip ':' */
             goto scanword;
@@ -919,6 +932,13 @@
 					scan_state->end = cp+1;
 					return TOKEN_LIT;
 				}
+				if (cp[1] == '%' && IS_LEX_DELIMIT(cp[2])) {
+					if (cp[2] == '"' || cp[2] == '/') { // no '%"" or '%/
+						scan_state->end = cp + 3;
+						return -TOKEN_LIT;
+					}
+					return TOKEN_LIT; // allowed '%
+				}
 			}
 			if (cp[1] == '\'') return -TOKEN_LIT; // no ''foo
             type = TOKEN_LIT;

src/tests/units/lexer-test.r3

@@ -46,6 +46,36 @@ Rebol [
 
 ===end-group===
 
+===start-group=== "Special % word"
+	--test-- "valid % word cases"
+		--assert word? try [load {%}]
+		--assert word? try [load {% }]
+		--assert word? try [load {%^-}]
+		--assert word? try [first load {[%]}]
+	--test-- "valid % lit-word cases"
+		--assert lit-word? try [load {'%}]
+		--assert lit-word? try [load {'% }]
+		--assert lit-word? try [load {'%^-}]
+		--assert lit-word? try [first load {['%]}]
+	--test-- "valid % get-word cases"
+		--assert get-word? try [load {:%}]
+		--assert get-word? try [load {:% }]
+		--assert get-word? try [load {:%^-}]
+		--assert get-word? try [first load {[:%]}]
+	--test-- "invalid % lit-word cases"
+		--assert all [error? e: try [load {'%""}] e/id = 'invalid e/arg1 = "word-lit"]
+		--assert all [error? e: try [load {'%/}]  e/id = 'invalid e/arg1 = "word-lit"]
+	--test-- "invalid % get-word cases"
+		--assert all [error? e: try [load {:%""}] e/id = 'invalid e/arg1 = "word-get"]
+		--assert all [error? e: try [load {:%/}]  e/id = 'invalid e/arg1 = "word-get"]
+	--test-- "% used in object"
+		--assert all [
+			not error? try [o: make object! [%: 1]]
+			1 = o/%
+		]
+
+===end-group===
+
 ===start-group=== "Email"
 	--test-- "valid `emails`"
 		--assert email? load {name@where}