Error message and docs for [replace] are misleading

[nrc]

e.g., Cargo.toml:

[workspace]
members = [
    ...
]

[replace]
"rls-data" = { path = "data" }

The error here is that the package id is missing a version number (changing rls-data to rls-data:0.7.0 fixed the problem). However, the error cargo gives is "no package or project section found.".

The documentation here is confusing too: this section states "Each key in the [replace] table is a package id specification" where "package id specification" links to http://doc.crates.io/pkgid-spec.html where the version appears optional, both in the grammar and the examples.

[alexcrichton]

I believe this error comes from this location where the logic looks like:

• Parse as a "real manifest"
• If that fails, parse as a "virtual manifest"
• If that fails, return the first error

It turns out in this situation both parsings fail, but the latter error is more relevant than the first, so we're throwing away the wrong error!