mbe: Rework diagnostics for metavariable expressions #142950
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| let Some(tt) = iter.next() else { | ||
| let err = errors::MveExpectedIdent { span: fallback_span, not_ident_label: None, context }; | ||
| return Err(psess.dcx().create_err(err)); | ||
| }; |
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I have mixed feelings about this, in general.
Now we take some typical parser errors, like "expected X, found Y", including "expected EOF, found Y" aka trailing tokens, and over-specialize them for the specific case of metavariable expressions.
Like for every "unexpected token" we create a separate "unexpected token ... in space!".
This is not scalable, parser code cannot be shared well if the errors are over-specialized.
For example, this specific change adds some specialized logic here, but leaves previously used parse_token and parse_ident_from_token unchanged.
If some improvements are made, they should go into parse_token and be general enough to improve all users of that function, not some single specific case.
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There is a bit more context; I have continued work on top of these changes that eliminates parse_ident_from_token and parse_token for a more specific error 847b9f7 and then reuses the new logic for expansion diagnostics b576c49 (those two patches are a bit messy yet). The total diff was just getting a bit large so I put this PR up as a portion that can stand on its own without touching concat too much. Created a draft with the (incomplete) rest just now #142975.
I'm happy to adjust the diagnostics further or break the PRs up differently if something else makes more sense to you. What would you prefer?
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I split the nonfunctional changes here to a new PR, #143245. I think this should make it a bit more straightforward to do the other changes here. |
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…ation, r=petrochenkov mbe: Add tests and restructure metavariable expressions Add tests that show better diagnostics, and factor `concat` handling to a separate function. Each commit message has further details. This performs the nonfunctional perparation for further changes such as rust-lang#142950 and rust-lang#142975 .
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Rollup merge of #143245 - tgross35:metavariable-expr-organization, r=petrochenkov mbe: Add tests and restructure metavariable expressions Add tests that show better diagnostics, and factor `concat` handling to a separate function. Each commit message has further details. This performs the nonfunctional perparation for further changes such as #142950 and #142975 .
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☔ The latest upstream changes (presumably #143267) made this pull request unmergeable. Please resolve the merge conflicts. |
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Give a more user-friendly diagnostic about the following:
* Invalid syntax within the `${...}` braces, including missing
parentheses or trailing tokens.
* Incorrect number of arguments passed to specific metavariable
expressions.
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Make the diagnostics for metavariable expressions more user-friendly. This mostly addresses syntactic errors; I will be following up with improvements to
concat(..).This is probably easiest to review by-commit, more details are in the messages.
r? @petrochenkov