[BUG][Go] useOneOfDiscriminatorLookup generates invalid variable names for `oneOf` with no discriminator

Bug Report Checklist

[x] Have you provided a full/minimal spec to reproduce the issue?
[x] Have you validated the input using an OpenAPI validator (example)?
[x] Have you tested with the latest master to confirm the issue still exists?
[x] Have you searched for related issues/PRs?
[x] What's the actual output vs expected output?
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Description

I'm trying to define a property in a schema that can be one of two types - a single date-time string or an array of strings. I'm using oneOf without a discriminator to do this. Also, in this same (rather large) schema, we have a few other instances of oneOf that do use discriminators, so we're setting useOneOfDiscriminatorLookup to true. The generated code looks something like this:

func (dst *BarProp) UnmarshalJSON(data []byte) error {
    var err error
    match := 0
    // try to unmarshal data into ArrayOfString
    err = json.Unmarshal(data, &dst.ArrayOfString)
    if err == nil {
        json[]string, _ := json.Marshal(dst.ArrayOfString)
        if string(json[]string) == "{}" { // empty struct
            dst.ArrayOfString = nil
        } else {
            match++
        }
    } else {
        dst.ArrayOfString = nil
    }

Note that json[]string isn't a valid variable name.

When I try it with useOneOfDiscriminatorLookup set to false, json[]string is named jsonArrayOfString, which compiles fine - this is what I'd expect the fix to do. In general, I'd expect the value of useOneOfDiscriminatorLookup to be irrelevant to code generated from a oneOf with no discriminator (more or less like what the linked issue seems to suggest).

openapi-generator version

7.5.0-SNAPSHOT

OpenAPI declaration file content or url

oneOf-array-of-strings.yaml

Generation Details

generate -g go -p useOneOfDiscriminatorLookup=true

Steps to reproduce

Related issues/PRs

[BUG][Go] UnmarshalJson has unused variable err if spec has oneOf without discriminator

Suggest a fix

I'm currently testing out just calling lambda.type-to-name in modules/openapi-generator/src/main/resources/go/model_oneof.mustache; specifically replacing the json{{.}} on line 61 with json{{#lambda.type-to-name}}{{{.}}}{{/lambda.type-to-name}}.

OpenAPITools / openapi-generator