Correctly implement negative array indices, other bugfixes

- check for negative string lengths
- handle negative values for emitInc/emitDec
- bugfix for parseInteger with leading minus
- fix set literals containing variables as elements

pcomp/emit.pas

@@ -1250,7 +1250,7 @@ begin
 		(* nothing to do *)
 	end
 	else
-	if amount <= MaxTinyOffset then
+	if (amount > 0) and (amount <= MaxTinyOffset) then
 		emitIns2Int('INC', amount)
 	else
 	begin
@@ -1266,7 +1266,7 @@ begin
 		(* nothing to do *)
 	end
 	else
-	if amount <= MaxTinyOffset then
+	if (amount > 0) and (amount <= MaxTinyOffset) then
 		emitIns2Int('DEC', amount)
 	else
 	begin

pcomp/pcomp.pas

@@ -2456,10 +2456,7 @@ begin
 	begin
 		digits := curToken.tokenText;
 		if matchTokenOrNot(MinusToken) then
-		begin
-			readNextToken;
 			digits := digits + curToken.tokenText;
-		end;
 		parseInteger := integerFromString(digits);
 	end;
 	readNextToken;
@@ -2812,6 +2809,8 @@ begin
 
 		if checkToken(CommaToken) then
 		begin
+			(* TODO: handle comma syntax for indexing a char
+				from an array of strings *)
 			if elType.baseType <> ArrayType then
 				errorExit2('invalid array subscript for', name)
 		end;
@@ -3231,10 +3230,22 @@ begin
 	readNextToken;
 end;
 
+(* Handle an array range part. Very similar to parseInteger
+   but additionally handles Boolean, Enum and Char types which
+   can be used for array indices *)
 procedure getRangePart(var value:integer; var typeReturn: TypeSpec);
 var cnst: ConstRef;
+    negate:boolean;
+	digits: string[12];
 begin
 	setBaseType(typeReturn, NoType);
+	negate := false;
+
+	if checkToken(MinusToken) then
+	begin
+		negate := true;
+		readNextToken;
+	end;
 
 	if checkToken(IdentToken) then
 	begin
@@ -3268,7 +3279,11 @@ begin
 	else
 	begin
 		setBaseType(typeReturn, IntegerType);
-		value := parseInteger;
+		digits := curToken.tokenText;
+		if negate then
+			insert('-', digits, 1);
+		value := integerFromString(digits);
+		readNextToken;
 	end;
 end;
 
@@ -3433,9 +3448,9 @@ begin
 				if savedType.baseType = NoType then
 					savedType := elementType;
 				emitLoadConstantInt(cnst^.intValue);
+				readNextToken;
 			end;
 			emitAddToSet;
-			readNextToken;
 		end
 		else if checkToken(NumberToken) then
 		begin
@@ -3999,6 +4014,8 @@ begin
 		begin
 			readNextToken;
 			length := parseInteger;
+			if length < 1 then
+				errorExit2('invalid string length', '');
 			matchToken(RBracketToken);
 		end;
 		typSpec.size := getStringMemSize(length);