fixes grammar typos [backport] (#19289)

(cherry picked from commit a61bbf7)

Author: Araq

compiler/parser.nim

@@ -582,10 +582,10 @@ proc parsePar(p: var Parser): PNode =
   #|         | 'finally' | 'except' | 'for' | 'block' | 'const' | 'let'
   #|         | 'when' | 'var' | 'mixin'
   #| par = '(' optInd
-  #|           ( &parKeyw (ifExpr \ complexOrSimpleStmt) ^+ ';'
-  #|           | ';' (ifExpr \ complexOrSimpleStmt) ^+ ';'
+  #|           ( &parKeyw (ifExpr / complexOrSimpleStmt) ^+ ';'
+  #|           | ';' (ifExpr / complexOrSimpleStmt) ^+ ';'
   #|           | pragmaStmt
-  #|           | simpleExpr ( ('=' expr (';' (ifExpr \ complexOrSimpleStmt) ^+ ';' )? )
+  #|           | simpleExpr ( ('=' expr (';' (ifExpr / complexOrSimpleStmt) ^+ ';' )? )
   #|                        | (':' expr (',' exprColonEqExpr     ^+ ',' )? ) ) )
   #|           optPar ')'
   #

doc/grammar.txt

@@ -37,10 +37,10 @@ parKeyw = 'discard' | 'include' | 'if' | 'while' | 'case' | 'try'
         | 'finally' | 'except' | 'for' | 'block' | 'const' | 'let'
         | 'when' | 'var' | 'mixin'
 par = '(' optInd
-          ( &parKeyw (ifExpr \ complexOrSimpleStmt) ^+ ';'
-          | ';' (ifExpr \ complexOrSimpleStmt) ^+ ';'
+          ( &parKeyw (ifExpr / complexOrSimpleStmt) ^+ ';'
+          | ';' (ifExpr / complexOrSimpleStmt) ^+ ';'
           | pragmaStmt
-          | simpleExpr ( ('=' expr (';' (ifExpr \ complexOrSimpleStmt) ^+ ';' )? )
+          | simpleExpr ( ('=' expr (';' (ifExpr / complexOrSimpleStmt) ^+ ';' )? )
                        | (':' expr (',' exprColonEqExpr     ^+ ',' )? ) ) )
           optPar ')'
 literal = | INT_LIT | INT8_LIT | INT16_LIT | INT32_LIT | INT64_LIT