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NLL Diagnostic Review 3: missing borrow error justifications for unions #57100

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davidtwco opened this issue Dec 24, 2018 · 0 comments
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NLL Diagnostic Review 3: missing borrow error justifications for unions #57100

davidtwco opened this issue Dec 24, 2018 · 0 comments
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A-NLL Area: Non-lexical lifetimes (NLL) NLL-diagnostics Working towards the "diagnostic parity" goal P-low Low priority

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For the ui/borrowck/borrowck-union-borrow.ast.nll.stderr test, the AST borrow checker indicates that the borrow of u.b is causing the borrow of the union u itself, thus justifying the complaint about the borrow of u.a.

However, the NLL borrow checker just says that u.b is already borrowed, which is less clear when its pointing at a borrow of u.a.
@davidtwco davidtwco added P-low Low priority A-NLL Area: Non-lexical lifetimes (NLL) NLL-diagnostics Working towards the "diagnostic parity" goal labels Dec 24, 2018
@davidtwco davidtwco self-assigned this Dec 24, 2018
@davidtwco davidtwco mentioned this issue Dec 24, 2018
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Centril added a commit to Centril/rust that referenced this issue Jan 13, 2019
@Centril
Rollup merge of rust-lang#57102 - davidtwco:issue-57100, r=nikomatsakis
ca1e379 
NLL: Add union justifications to conflicting borrows.

Fixes rust-lang#57100.

This PR adds justifications to error messages for conflicting borrows of union fields.

Where previously an error message would say ``cannot borrow `u.b` as mutable..``, it now says ``cannot borrow `u` (via `u.b`) as mutable..``.

r? @pnkfelix
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A-NLL Area: Non-lexical lifetimes (NLL) NLL-diagnostics Working towards the "diagnostic parity" goal P-low Low priority
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