Nested errors and diagnostic

[romch007]

I'm trying to use miette to have nice error messages in a compiler I made, but I can't figure out how to properly do it. I've reproduced a minimal example:

use miette::{NamedSource, SourceSpan};

#[derive(Debug, miette::Diagnostic, thiserror::Error)]
enum AppError {
    #[error("analyze error")]
    AnalyzerError(
        #[diagnostic_source]
        #[source]
        AnalyzerError,
    ),
}

#[derive(Debug, miette::Diagnostic, thiserror::Error)]
enum AnalyzerError {
    #[error("variable '{varname}' already defined")]
    #[diagnostic(code(variable_already_defined))]
    VariableAlreadyDefined {
        varname: String,

        #[source_code]
        src: NamedSource<String>,

        #[label("here")]
        definition: SourceSpan,

        #[label("first defined here")]
        first_definition: SourceSpan,
    },

    #[error("variable '{varname}' not found")]
    #[diagnostic(code(variable_not_found))]
    VariableNotFound {
        varname: String,

        #[source_code]
        src: NamedSource<String>,

        #[label("used here")]
        used: SourceSpan,
    },
}

fn main() -> miette::Result<(), AppError> {
    let src = "entier a = 5;\necrire(a);\nentier a = 7;".to_string();

    Err(AppError::AnalyzerError(
        AnalyzerError::VariableAlreadyDefined {
            varname: "a".to_string(),
            src: NamedSource::new("testing.flo", src),
            first_definition: (0, 12).into(),
            definition: (25, 12).into(),
        },
    ))?;

    Ok(())
}

But this just prints Error: AnalyzerError(VariableAlreadyDefined { ... }) in terminal, not the fancy diagnostic message (I've enabled the fancy feature). Any help would be much appreciated!