parser enhancement: allow keywords after dots

compiler/parser.nim

@@ -39,6 +39,9 @@ type
     inPragma*: int             # Pragma level
     inSemiStmtList*: int
 
+  SymbolMode = enum
+    smNormal, smAllowNil, smAfterDot
+
 proc parseAll*(p: var TParser): PNode
 proc closeParser*(p: var TParser)
 proc parseTopLevelStmt*(p: var TParser): PNode
@@ -62,7 +65,7 @@ proc optPar*(p: var TParser)
 proc optInd*(p: var TParser, n: PNode)
 proc indAndComment*(p: var TParser, n: PNode)
 proc setBaseFlags*(n: PNode, base: TNumericalBase)
-proc parseSymbol*(p: var TParser, allowNil = false): PNode
+proc parseSymbol*(p: var TParser, mode = smNormal): PNode
 proc parseTry(p: var TParser; isExpr: bool): PNode
 proc parseCase(p: var TParser): PNode
 proc parseStmtPragma(p: var TParser): PNode
@@ -304,13 +307,24 @@ proc colcom(p: var TParser, n: PNode) =
   eat(p, tkColon)
   skipComment(p, n)
 
-proc parseSymbol(p: var TParser, allowNil = false): PNode =
+proc parseSymbol(p: var TParser, mode = smNormal): PNode =
   #| symbol = '`' (KEYW|IDENT|literal|(operator|'('|')'|'['|']'|'{'|'}'|'=')+)+ '`'
-  #|        | IDENT | 'addr' | 'type'
+  #|        | IDENT | KEYW
   case p.tok.tokType
-  of tkSymbol, tkAddr, tkType:
+  of tkSymbol:
     result = newIdentNodeP(p.tok.ident, p)
     getTok(p)
+  of tokKeywordLow..tokKeywordHigh:
+    if p.tok.tokType == tkAddr or p.tok.tokType == tkType or mode == smAfterDot:
+      # for backwards compatibility these 2 are always valid:
+      result = newIdentNodeP(p.tok.ident, p)
+      getTok(p)
+    elif p.tok.tokType == tkNil and mode == smAllowNil:
+      result = newNodeP(nkNilLit, p)
+      getTok(p)
+    else:
+      parMessage(p, errIdentifierExpected, p.tok)
+      result = ast.emptyNode
   of tkAccent:
     result = newNodeP(nkAccQuoted, p)
     getTok(p)
@@ -335,10 +349,6 @@ proc parseSymbol(p: var TParser, allowNil = false): PNode =
         parMessage(p, errIdentifierExpected, p.tok)
         break
     eat(p, tkAccent)
-  else:
-    if allowNil and p.tok.tokType == tkNil:
-      result = newNodeP(nkNilLit, p)
-      getTok(p)
   else:
     parMessage(p, errIdentifierExpected, p.tok)
     # BUGFIX: We must consume a token here to prevent endless loops!
@@ -390,7 +400,7 @@ proc dotExpr(p: var TParser, a: PNode): PNode =
   result = newNodeI(nkDotExpr, info)
   optInd(p, result)
   addSon(result, a)
-  addSon(result, parseSymbol(p))
+  addSon(result, parseSymbol(p, smAfterDot))
 
 proc qualifiedIdent(p: var TParser): PNode =
   #| qualifiedIdent = symbol ('.' optInd symbol)?
@@ -1005,10 +1015,10 @@ proc isExprStart(p: TParser): bool =
     result = true
   else: result = false
 
-proc parseSymbolList(p: var TParser, result: PNode, allowNil = false) =
+proc parseSymbolList(p: var TParser, result: PNode) =
   # progress guaranteed
   while true:
-    var s = parseSymbol(p, allowNil)
+    var s = parseSymbol(p, smAllowNil)
     if s.kind == nkEmpty: break
     addSon(result, s)
     if p.tok.tokType != tkComma: break
@@ -1029,7 +1039,7 @@ proc parseTypeDescKAux(p: var TParser, kind: TNodeKind,
     getTok(p)
     let list = newNodeP(nodeKind, p)
     result.addSon list
-    parseSymbolList(p, list, allowNil = true)
+    parseSymbolList(p, list)
 
 proc parseExpr(p: var TParser): PNode =
   #| expr = (ifExpr

doc/grammar.txt

@@ -22,7 +22,7 @@ plusExpr = mulExpr (OP8 optInd mulExpr)*
 mulExpr = dollarExpr (OP9 optInd dollarExpr)*
 dollarExpr = primary (OP10 optInd primary)*
 symbol = '`' (KEYW|IDENT|literal|(operator|'('|')'|'['|']'|'{'|'}'|'=')+)+ '`'
-       | IDENT | 'addr' | 'type'
+       | IDENT | KEYW
 exprColonEqExpr = expr (':'|'=' expr)?
 exprList = expr ^+ comma
 dotExpr = expr '.' optInd symbol
@@ -81,7 +81,6 @@ paramList = '(' declColonEquals ^* (comma/semicolon) ')'
 paramListArrow = paramList? ('->' optInd typeDesc)?
 paramListColon = paramList? (':' optInd typeDesc)?
 doBlock = 'do' paramListArrow pragmas? colcom stmt
-doBlocks = doBlock ^* IND{=}
 procExpr = 'proc' paramListColon pragmas? ('=' COMMENT? stmt)?
 distinct = 'distinct' optInd typeDesc
 expr = (ifExpr
@@ -98,7 +97,8 @@ primary = typeKeyw typeDescK
 typeDesc = simpleExpr
 typeDefAux = simpleExpr
            | 'concept' typeClass
-macroColon = ':' stmt? ( IND{=} 'of' exprList ':' stmt
+postExprBlocks = ':' stmt? ( IND{=} doBlock
+                           | IND{=} 'of' exprList ':' stmt
                            | IND{=} 'elif' expr ':' stmt
                            | IND{=} 'except' exprList ':' stmt
                            | IND{=} 'else' ':' stmt )*