语法冲突-减少减少冲突稀疏

Question

Im get a conflict reduce-reduce in the below code , ive tried almost all i ideas i came up with to solving it heres the report of the problem, this is a BNF->Gold parser conversion any ideas to solve it i would aprreciate it

<Constructor> ::= <Type> '{' <SetCons_RecordCons_ArrayCons_Optional> '}'

<SetCons_RecordCons_ArrayCons_Optional> ::= <>
                                          | <SetCons>
                                          | <RecordCons>
                                          | <ArrayCons>
                !| <Type> '{' <SetCons> '}'
                !| <Type> '(' <RecordCons> '}'
                !| <Type> '(' <ArrayCons> ')'

!SetCons = SetElt {"," SetElt}  Inclui o SetElt
<SetCons> ::= <Expr>
            | <Expr> '..' <Expr>
            | <Expr> ',' <SetCons>
            | <Expr> '..' <Expr> ',' <SetCons>

!SetElt = Expr [".." Expr]
!<SetElt> ::= <Expr>
           !| <Expr> '..' <Expr>

!RecordCons = RecordElt {"," RecordElt}    inclui o recordElt
<RecordCons> ::= <Expr>
               | <Expr> <RecordCons>
               | <Expr> ',' <RecordCons>
               | Id ':=' <Expr> ',' <RecordCons>

!RecordElt = [Id ":="] Expr
!<RecordElt> ::= <Expr>
!             | Id ':=' <Expr>

!ArrayCons =  Expr {"," Expr} ["," ".."]
<ArrayCons> ::= <Expr> ',' <ArrayCons>
              | <Expr> ',' '..'
              | <Expr>

Here is the report:

2. Reduce-Reduce conflict for the symbol '}'

Productions in Conflict

When the parser encounters '}', more than one production can be completed (reduced):

<SetCons> ::= <Expr> •
<RecordCons> ::= <Expr> •
<ArrayCons> ::= <Expr> •

Reduce Production #1

The production below can be followed by '}' :

<SetCons> ::= <Expr> •

Because... '}' directly follows <SetCons_RecordCons_ArrayCons_Optional>.

<Constructor> ::= <Type> '{' • <SetCons_RecordCons_ArrayCons_Optional> '}' 

Reduce Production #2

The production below can be followed by '}' :

<RecordCons> ::= <Expr> •

Because... '}' directly follows <SetCons_RecordCons_ArrayCons_Optional>.

<Constructor> ::= <Type> '{' • <SetCons_RecordCons_ArrayCons_Optional> '}' 

Reduce Production #3

The production below can be followed by '}' :

<ArrayCons> ::= <Expr> •

Because... '}' directly follows <SetCons_RecordCons_ArrayCons_Optional>.

<Constructor> ::= <Type> '{' • <SetCons_RecordCons_ArrayCons_Optional> '}' 

Answer 1

The Gold Parser diagnosis seems to be quite detailed, and it certainly contains all the information you need.

But to put it simply, any of SetCons , RecordCons or ArrayCons can be an Expr . So it is possible for the input to be simply:

<Type> { <Expr> }

in which case, the parser cannot know which of those three non-terminals it should reduce the Expr to.