How to read errors

[PFAhard]

I'm getting an error when parsing this line (it's part of a Solidity document that I'm parsing with rust pest):

using VaultLibrary for Vault;

Error { 
    variant: ParsingError { 
        positives: [memberTypeName, elementaryTypeName, functionTypeName, mappingType], 
        negatives: []
    }, 
    location: Pos(930), 
    line_col: Pos((30,28)), 
    path: None, 
    line: "    using VaultLibrary for Vault;", 
    continued_line: None
}

this is the main parts of parser for this expression:

typeName = {
    memberTypeName |
    atomicTypeName 
}
atomicTypeName = {
    elementaryTypeName | functionTypeName | mappingType | identifierPath 
}
memberTypeName = {
    atomicTypeName ~ LBrack ~ nonLeftExpression? ~ RBrack
}
elementaryTypeName = { 
    Address ~ Payable? |
    Bool |
    String |
    Bytes | 
    SignedIntegerType | 
    UnsignedIntegerType | 
    FixedBytes | 
    Fixed | 
    Ufixed
 }
functionTypeName = {
    Function ~ LParen ~ (parameterList)? ~ RParen ~
    (
        visibility
        | stateMutability
    )* ~
    (Returns ~ LParen ~ parameterList ~ RParen)?
}
mappingType = {
    Mapping ~ LParen ~ mappingKeyType ~ DoubleArrow ~ typeName ~ RParen
}
identifierPath = @{
    Identifier ~ (PeriodAtom ~ Identifier)*
}
Identifier = @{ IdentifierStart ~ (IdentifierPart)* }
IdentifierStart = _{ 'a'..'z' | 'A'..'Z' | "$" | "_" }
IdentifierPart = _{ 'a'..'z' | 'A'..'Z' | '0'..'9' | "$" | "_" }

I will be glad if you explain what the problem is in this case, but it would be better if you explain how to "read" the rust pest errors in general.

what does positives mean? How can they all be positive if they are different? How can I figure out which rule is failing (I have a guess for this case, but I'm asking about errors in general)?

It would be better to see the last successful rule or more descriptive reasons for the error.

[PFAhard]

I found the cause of this error, but it's still interesting to understand the errors in general