Reland: [clang] Implement code synthesis context for checking template parameters #130603
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Keeping in draft form while I investigate the performance regression reported here: #126088 (comment) |
cor3ntin
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…late parameters) (#150823) This is a first pass at implementing [P2841R7](https://www.open-std.org/jtc1/sc22/wg21/docs/papers/2025/p2841r7.pdf). The implementation is far from complete; however, I'm aiming to do that in chunks, to make our lives easier. In particular, this does not implement - Subsumption - Mangling - Satisfaction checking is minimal as we should focus on #141776 first (note that I'm currently very stuck) FTM, release notes, status page, etc, will be updated once the feature is more mature. Given the state of the feature, it is not yet allowed in older language modes. Of note: - Mismatches between template template arguments and template template parameters are a bit wonky. This is addressed by #130603 - We use `UnresolvedLookupExpr` to model template-id. While this is pre-existing, I have been wondering if we want to introduce a different OverloadExpr subclass for that. I did not make the change in this patch.
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…rameters Instead of manually adding a note pointing to the relevant template parameter to every relevant error, which is very easy to miss, this patch adds a new instantiation context note, so that this can work using RAII magic. This fixes a bunch of places where these notes were missing, and is more future-proof. Some diagnostics are reworked to make better use of this note: - Errors about missing template arguments now refer to the parameter which is missing an argument. - Template Template parameter mismatches now refer to template parameters as parameters instead of arguments. It's likely this will add the note to some diagnostics where the parameter is not super relevant, but this can be reworked with time and the decrease in maintenance burden makes up for it. This bypasses the templight dumper for the new context entry, as the tests are very hard to update. This depends on #125453, which is needed to avoid losing the context note for errors occuring during template argument deduction. Original PR: #126088
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Instead of manually adding a note pointing to the relevant template parameter to every relevant error, which is very easy to miss, this patch adds a new conde synthesis context note, so that this can work using RAII magic.
This fixes a bunch of places where these notes were missing, and is more future-proof.
Some diagnostics are reworked to make better use of this note:
It's likely this will add the note to some diagnostics where the parameter is not super relevant, but this can be reworked with time and the decrease in maintenance burden makes up for it.
This bypasses the templight dumper for the new context entry, as the tests are very hard to update.
This depends on #125453, which is needed to avoid losing the context note for errors occuring during template argument deduction.
Original PR: #126088