The following:

Foo[^foo]
Bar[^bar]

[^foo]:
    FooDef1
    FooDef2

[^bar]:
    BarDef

renders like so on GitHub:

but pulldown_cmark::Parser gets confused:

1. It sees the definition text as indented code blocks.
2. It does not see the end of the first definition before the start of the second.

Running the following code:

static MARKDOWN: &str = r#"\
Foo[^foo]
Bar[^bar]

[^foo]:
    FooDef1
    FooDef2

[^bar]:
    BarDef
"#;

fn main() {
    use pulldown_cmark::{Options, Parser};
    let options = Options::empty().union(Options::ENABLE_FOOTNOTES);
    let parser = Parser::new_ext(MARKDOWN, options);
    for event in parser {
        eprintln!("{event:?}");
    }
}

yields the following events:

• Start(Paragraph)
• HardBreak
• Text(Borrowed("Foo"))
• FootnoteReference(Borrowed("foo"))
• SoftBreak
• Text(Borrowed("Bar"))
• FootnoteReference(Borrowed("bar"))
• End(Paragraph)
• Start(FootnoteDefinition(Borrowed("foo")))
• Start(CodeBlock(Indented))
• Text(Borrowed("FooDef1\n"))
• Text(Borrowed("FooDef2\n"))
• End(CodeBlock(Indented))
• Start(FootnoteDefinition(Borrowed("bar")))
• Start(CodeBlock(Indented))
• Text(Borrowed("BarDef\n"))
• End(CodeBlock(Indented))
• End(FootnoteDefinition(Borrowed("bar")))
• End(FootnoteDefinition(Borrowed("foo")))

I would expect it to:

• treat the indented definitions as part of the definition, and
• end the first definition before starting the second.

There is a workaround:

Foo[^foo]
Bar[^bar]

[^foo]: FooDef1
    FooDef2

[^bar]: BarDef

This yields:

• ...
• Start(FootnoteDefinition(Borrowed("foo")))
• Start(Paragraph)
• Text(Borrowed("FooDef1"))
• SoftBreak
• Text(Borrowed("FooDef2"))
• End(Paragraph)
• End(FootnoteDefinition(Borrowed("foo")))
• Start(FootnoteDefinition(Borrowed("bar")))
• Start(Paragraph)
• Text(Borrowed("BarDef"))
• End(Paragraph)
• End(FootnoteDefinition(Borrowed("bar")))

i.e. by putting content on the same line as the definition begins, the parser is happy. Unfortunately, at least one code formatter in VSCode for Markdown (maybe the built-in one?) likes to format long definitions indented below the [^foo]: opener.