suggest workspace hints for boolean dependencies

[borngraced]

What does this PR try to resolve?

via issue #15505, Cargo currently errors on

[dependencies]
crc32fast = true

with a message about expected a version string or a detailed dependency It doesn’t hint that you can depend on a workspace member. This PR updates cargo so that when you write dep = true, the error also suggests:

dep = { workspace = true }
dep.workspace = true

How should we test and review this PR?

In a workspace crate’s Cargo.toml, add

[dependencies]
crc32fast = true

Run cargo build and you should see the enhanced error with the two workspace hints.

Additional information

Regarding support for int/float, we only need a special case for boolean because they’re the only values that get the workspace hint. Everything else just uses the normal detailed dependency error

[rustbot]

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[epage]

Mind squashing that last commit into the previous one?