Implement a '#' prefix for raw identifiers that may alias keywords (#1480)

* Implement a '#' prefix for raw identifiers that may alias keywords

* Review comments

* Disallow hashless raw identifiers in interpolations

* Run clang-format

man/rgbasm.5

@@ -1068,7 +1068,20 @@ Additionally, label names can contain up to a single dot
 .Ql \&. ,
 which may not be the first character.
 .Pp
-A symbol cannot have the same name as a reserved keyword.
+A symbol cannot have the same name as a reserved keyword, unless it is prefixed by a hash
+.Sq # .
+For example,
+.Ql #load
+denotes a symbol named
+.Ql load ,
+and
+.Ql #LOAD
+denotes a different symbol named
+.Ql LOAD ;
+in both cases the
+.Sq #
+prevents them from being treated as the keyword
+.Ic LOAD .
 .Ss Labels
 One of the assembler's main tasks is to keep track of addresses for you, so you can work with meaningful names instead of
 .Dq magic

src/asm/lexer.cpp

@@ -596,7 +596,16 @@ static uint32_t readBracketedMacroArgNum() {
 
 	if (c >= '0' && c <= '9') {
 		num = readNumber(10, 0);
-	} else if (startsIdentifier(c)) {
+	} else if (startsIdentifier(c) || c == '#') {
+		if (c == '#') {
+			shiftChar();
+			c = peek();
+			if (!startsIdentifier(c)) {
+				error("Empty raw symbol in bracketed macro argument\n");
+				return 0;
+			}
+		}
+
 		std::string symName;
 
 		for (; continuesIdentifier(c); c = peek()) {
@@ -1138,8 +1147,7 @@ static bool continuesIdentifier(int c) {
 	return startsIdentifier(c) || (c <= '9' && c >= '0') || c == '#' || c == '@';
 }
 
-static Token readIdentifier(char firstChar) {
-	// Lex while checking for a keyword
+static Token readIdentifier(char firstChar, bool raw) {
 	std::string identifier(1, firstChar);
 	int tokenType = firstChar == '.' ? T_(LOCAL_ID) : T_(ID);
 
@@ -1155,9 +1163,13 @@ static Token readIdentifier(char firstChar) {
 			tokenType = T_(LOCAL_ID);
 	}
 
-	// Attempt to check for a keyword
-	auto search = keywordDict.find(identifier.c_str());
-	return search != keywordDict.end() ? Token(search->second) : Token(tokenType, identifier);
+	// Attempt to check for a keyword if the identifier is not raw
+	if (!raw) {
+		if (auto search = keywordDict.find(identifier.c_str()); search != keywordDict.end())
+			return Token(search->second);
+	}
+
+	return Token(tokenType, identifier);
 }
 
 // Functions to read strings
@@ -1207,6 +1219,19 @@ static std::shared_ptr<std::string> readInterpolation(size_t depth) {
 	// Don't return before `lexerState->disableInterpolation` is reset!
 	lexerState->disableInterpolation = disableInterpolation;
 
+	if (fmtBuf.starts_with('#')) {
+		// Skip a '#' raw identifier prefix, but after expanding any nested interpolations.
+		fmtBuf.erase(0, 1);
+	} else if (keywordDict.find(fmtBuf.c_str()) != keywordDict.end()) {
+		// Don't allow symbols that alias keywords without a '#' prefix.
+		error(
+		    "Interpolated symbol \"%s\" is a reserved keyword; add a '#' prefix to use it as a raw "
+		    "symbol\n",
+		    fmtBuf.c_str()
+		);
+		return nullptr;
+	}
+
 	Symbol const *sym = sym_FindScopedValidSymbol(fmtBuf);
 
 	if (!sym || !sym->isDefined()) {
@@ -1781,8 +1806,13 @@ static Token yylex_NORMAL() {
 			// Handle identifiers... or report garbage characters
 
 		default:
+			bool raw = c == '#';
+			if (raw && startsIdentifier(peek())) {
+				c = nextChar();
+			}
+
 			if (startsIdentifier(c)) {
-				Token token = readIdentifier(c);
+				Token token = readIdentifier(c, raw);
 
 				// An ELIF after a taken IF needs to not evaluate its condition
 				if (token.type == T_(POP_ELIF) && lexerState->lastToken == T_(NEWLINE)
@@ -2017,7 +2047,7 @@ static Token skipIfBlock(bool toEndc) {
 
 			if (startsIdentifier(c)) {
 				shiftChar();
-				switch (Token token = readIdentifier(c); token.type) {
+				switch (Token token = readIdentifier(c, false); token.type) {
 				case T_(POP_IF):
 					lexer_IncIFDepth();
 					break;
@@ -2103,7 +2133,7 @@ static Token yylex_SKIP_TO_ENDR() {
 
 			if (startsIdentifier(c)) {
 				shiftChar();
-				switch (readIdentifier(c).type) {
+				switch (readIdentifier(c, false).type) {
 				case T_(POP_FOR):
 				case T_(POP_REPT):
 					depth++;
@@ -2250,7 +2280,7 @@ Capture lexer_CaptureRept() {
 		} while (isWhitespace(c));
 		// Now, try to match `REPT`, `FOR` or `ENDR` as a **whole** identifier
 		if (startsIdentifier(c)) {
-			switch (readIdentifier(c).type) {
+			switch (readIdentifier(c, false).type) {
 			case T_(POP_REPT):
 			case T_(POP_FOR):
 				depth++;
@@ -2303,7 +2333,7 @@ Capture lexer_CaptureMacro() {
 		} while (isWhitespace(c));
 		// Now, try to match `ENDM` as a **whole** identifier
 		if (startsIdentifier(c)) {
-			switch (readIdentifier(c).type) {
+			switch (readIdentifier(c, false).type) {
 			case T_(POP_ENDM):
 				endCapture(capture);
 				// The ENDM has been captured, but we don't want it!

test/asm/empty-raw-identifier.asm

@@ -0,0 +1,5 @@
+MACRO #macro
+	println "all args: \#"
+	println "bad args: \<?>, \<#>"
+ENDM
+	#macro a, #b, c, 1, #2, 3

test/asm/empty-raw-identifier.err

@@ -0,0 +1,5 @@
+error: empty-raw-identifier.asm(5) -> empty-raw-identifier.asm::macro(3):
+    Invalid character in bracketed macro argument '?'
+error: empty-raw-identifier.asm(5) -> empty-raw-identifier.asm::macro(3):
+    Empty raw symbol in bracketed macro argument
+error: Assembly aborted (2 errors)!

test/asm/empty-raw-identifier.out

@@ -0,0 +1,2 @@
+all args: a,#b,c,1,#2,3
+bad args: >, >

test/asm/interpolation.asm

@@ -27,3 +27,6 @@ PRINTLN "label {label}"
 MACRO foo
 ENDM
 PRINTLN "foo {foo}"
+
+; hashless keyword
+PRINTLN "xor {xor}"

test/asm/interpolation.err

@@ -4,4 +4,6 @@ error: interpolation.asm(22):
     Interpolated symbol "label" does not exist
 error: interpolation.asm(29):
     Interpolated symbol "foo" is not a numeric or string symbol
-error: Assembly aborted (3 errors)!
+error: interpolation.asm(32):
+    Interpolated symbol "xor" is a reserved keyword; add a '#' prefix to use it as a raw symbol
+error: Assembly aborted (4 errors)!

test/asm/interpolation.out

@@ -3,3 +3,4 @@ undef
 label 
 label $7E
 foo 
+xor 

test/asm/raw-identifiers.asm

@@ -0,0 +1,36 @@
+def #DEF equ 1
+def #def equ 2
+def #ghi equ 3
+export #def, #ghi
+
+def #align = 0
+def #rb rb #def
+
+MACRO #macro
+	println "\<#def> is not \<#DEF>"
+ENDM
+	#macro first, second
+	purge #macro
+	assert !def(#macro)
+
+section "section", rom0
+#section::
+	dw #section
+#.rom0:
+	db BANK(#section.rom0)
+#section.romx:
+	println "section.romx is in ", SECTION(.romx)
+
+def #sub equs "def"
+{#sub} #add equs "#"
+
+for #for, {{#add}{#sub}}
+	println "for == ", #for
+endr
+	assert #for == 2
+	assert !{#sub}(#FOR)
+
+	newcharmap #charmap, #main
+	charmap "#", $42
+	setcharmap #charmap
+	db "#"

test/asm/raw-identifiers.out

@@ -0,0 +1,4 @@
+second is not first
+section.romx is in section
+for == $0
+for == $1