No viable input ANTLR4

Question

currently having some parsing issues with my grammar and I just can't figure out what is going wrong..

Here's my grammar:

grammar Demo;

@header {
    import java.util.List;
    import java.util.ArrayList;
}

program:
    functionList                                                                #programFunction
    ;

functionList:
    function*
    ;

function:
    'haupt()' '{' stmntList '}'                                                     #hauptFunction
    | type='zahl' ID '(' paramList ')' '{' stmntList '}'                            #zahlFunction
    | type='Zeichenkette' ID '(' paramList ')' '{' stmntList '}'                    #zeichenketteFunction
    | type='nix' ID '(' paramList ')' '{' stmntList '}'                             #nixFunction
    ;

paramList:
    param (',' paramList)?
    ;

param:
    'zahl' ID                                       
    | 'Zeichenkette' ID     
    |                                   
    ;

variableList:
    ID (',' variableList)?
    ;


stmntList:
    stmnt (stmntList)?                                      
    ;

stmnt:
    'zahl' varName=ID ';'                                                               #zahlStmnt
    | 'Zeichenkette' varName=ID ';'                                                     #zeichenketteStmnt
    |  varName=ID '=' varValue=expr ';'                                                 #varAssignment
    | 'Schreibe' '(' argument=expr ')' ';'                                  #schreibeImmediat 
    | 'Schreibe''(' argument=ID ')'     ';'                                     #schreibeText
    | 'zuZeichenkette' '(' ID ')'';'                                            #convertString
    | 'zuZahl''('ID')'';'                                                       #convertInteger
    | 'wenn' '(' boolExpr ')' '{' stmntList '}'  ('sonst' '{' stmntList '}')?   #wennsonstStmnt 
    | 'fuer' '(' ID '=' expr ',' boolExpr ',' stmnt ')' '{' stmntList '}'       #forLoop    
    | 'waehrend' '(' boolExpr ')' '{' stmntList '}'                             #whileLoop
    | 'tu' '{' stmntList '}' 'waehrend' '(' boolExpr ')'    ';'                     #doWhile
    | 'return' expr             ';'                                             #returnVar
    | fctName=ID '(' (variableList)? ')'';'                                     #functionCall               
    ;

boolExpr:
    boolParts ('&&' boolExpr)?                                                  #logicAnd
    | boolParts ('||' boolExpr)?                                                #logicOr
    ;

boolParts:
    expr '==' expr                                                              #isEqual
    | expr '!=' expr                                                            #isUnequal
    | expr '>' expr                                                             #biggerThan
    | expr '<' expr                                                             #smallerThan
    | expr '>=' expr                                                            #biggerEqual
    | expr '<=' expr                                                            #smallerEqual
    ;

expr:
    links=expr '+' rechts=product                   #addi
    | links = expr '-' rechts=product               #diff
    |product                            #prod
    ;

product:
    links=product '*' rechts=factor                 #mult
    | links=product '/' rechts=factor               #teil
    | factor                            #fact
    ;

factor:
    '(' expr')'                         #bracket
    | var=ID                                #var
    | zahl=NUMBER                           #numb
    ;


ID  :       [a-zA-Z]+;
NUMBER  :   '0'|[1-9][0-9]*;
WS:         [\r\n\t ]+ -> skip ;

And this is the code I am trying to parse:

haupt() {
    zahl zz; 
    zz = 2;
    zahl cc;
    cc = 3;

    zz = zz+cc;
    Schreibe(cc+cc+cc);     
}   

the problems arise already in the first row, telling me that it expects a '{' instead of ' '. This is something I cannot understand since I skipped all WS in my grammar. Next errors are the wrong recognition of the 2nd row: the variable declaration of "zahl zz;" is not understood as it should be: the first grammar rule of stmnt should work it, but it does not...

Here are the errors antlrs TestRig gives me:

line 2:6 no viable alternative at input 'zahlzz'
line 4:6 no viable alternative at input 'zahlcc'
line 9:12 mismatched input '+' expecting ')'

Thanks for your help! Tim

Answer 1

When I see a weird nonsensical bugaboo like this, it generally means that there is a token mismatch between what the lexer and parser think the token types are. Make sure the you regenerate all of your grammars using ANTLR and recompile everything. Hopefully that will clear it up.