Allow `auto` as a return type for functions. Only support functions with one `return` statement for now (open question).
This explicitly suggests removing the executable semantics `fn name(args) => expression` syntax, and is motivated by reconciling executable semantics with approved Carbon state. [example](https://github.com/carbon-language/carbon-lang/blob/3d1716f6c692a840d8b4b513ddfb8119432a5150/executable_semantics/testdata/fun_named_params.carbon) This aspect is a decision that may be affected by lambda syntax, but we might also choose to keep lambda syntax and function syntax separate -- I don't think there's enough benefit to providing the alternate function syntax right now.
Co-authored-by: Geoff Romer <gromer@google.com>
Co-authored-by: Chandler Carruth <chandlerc@gmail.com>
Proposal to support a limited set of implicit conversions.
This would generally permit only implicit conversions that are lossless and semantics-preserving. In particular, this proposal allows:
- Conversion from an integer type to a wider integer type of the same signedness, and from an unsigned integer type to a wider signed integer type.
- Conversion from an integer type to a floating-point type that has enough mantissa bits to exactly represent all integers in the source type.
- Conversion from integer literals to integer and floating-point types that can represent them.
- Conversion from floating-point literals to floating-point types that can represent them.
- Conversions required for generics: conversions of values between facet types, and conversions of types between type-of-types, as described in the generics proposals.
- Conversions required for inheritance: derived-to-base conversions for class pointers and class values.
Other conversions, such as lossy conversions between arithmetic types and conversions between bool and other types are not supported.
Co-authored-by: josh11b <josh11b@users.noreply.github.com>
Co-authored-by: Chandler Carruth <chandlerc@gmail.com>
Co-authored-by: Geoff Romer <gromer@google.com>
The big change here is to enable libc++'s debug mode outside of `opt`
builds on Linux where it seems to work well with the Homebrew installed
toolchain. I'm restricting it to Linux as the system libc++ install on
x86 macOS doesn't seem to work. This is based on and subsumes #811.
This also tidies up how `-NDEBUG` is set to include non-codegen compile
actions, and consolidates some optimization flags in a single location.
This part has no functionality change, but would likely invalidate
caches so bundled here where both a) I noticed and b) we already had
a cache invalidation.
Only the special nullability attributes (`_Nonnull`) work correctly
through type aliases like we're using with `Ptr`. But they aren't
strictly UB and so have to be specially enabled in our sanitizer config
in order to usefully catch nullness errors early. Turn on those
sanitizers as well.
Also, now that we are using fully remote build output caching for our
CI and not trying to squeeze under an arbitrary size limit, re-enable
the nice error messages for all the UBSan checks.
Note that this will have a (very) slow CI run as it will have to
recompile ~everything and upload fresh artifacts. But those should then
be effective cache hits going forward.
The advantage is a C++ pointer is special, and this approach eliminates the Ptr class type that was causing problems in conversions. Attribute suggestion was courtesy of chandlerc. We're sticking with the Ptr name because it's shorter than Nonnull, and we're likely to keep this in lots of places.
There's a small update to update_checks.py to handle the recursive directories. Also, I'm only using one level of nesting in this PR but really no reason we can't do more. I'm just not sure what clustering is best right now.
As a pattern, I'm trying to name all failing tests `fail_*.carbon`.
I'm seeing if I can upstream thundergolfer/bazel-mypy-integration#43, but we can also point at my fork for the time being.
This should resolve conflicts with mypy treating imports as non-hermetic, creating inconsistent behavior if packages are/aren't installed locally.
With this, only main.cpp instantiates an arena. Maybe we'll want to split that up more later (e.g., so that the runtime interpreter uses its own arena), but given the intent to have type-checking update the AST, I thought this was a reasonable approach for now in order to avoid ownership complexities.
Fixes#769
* Debugging quality-of-life improvements
- Use std::abort for `CHECK`/`FATAL` failures, which acts as a debugger breakpoint as well as automatically printing a stack trace.
- Re-enable printing continuations in `--trace` mode.
- Log the source location of each step in `--trace` mode.
Co-authored-by: Jon Meow <46229924+jonmeow@users.noreply.github.com>
These aren't really statements (because they're not executed at run time), and it's debatable whether they're declarations, since their primary purpose isn't to introduce a name. On Discord, "directive" seemed to be the consensus choice for an alternate term.
Also apply it to the list of tokens. This way there's no need for "sort order" comments.
This was a side-effect of me trying to merge in api/impl/library/package, and thinking "why am I doing this manually?"
Co-authored-by: Geoff Romer <gromer@google.com>
Doesn't add much logic, only takes advantage of parser structure for the ordering enforcement.
Note import_nonexistent tests should probably fail, but writing import tests needs a chain of functionality, and I figured I'd just start adding some to validate the syntax (not adding existent imports because that'd require multi-file structure).
This is based on discussion on #732: that we should probably parse the invalid whitespace, then reject it as part of string validation, rather than having different parses. I worry the question of "how is this parsed" may lead to subtly unexpected results if we aren't consistent, so I'm switching the logic from the lexer to the unescape library (and also adjusting the list of rejected whitespace).
Along with #789 this addresses most of #769 although global_arena is still a TODO (that's widespread and overlaps with other changes so I wanted to do it after these are in).
Related to discussion on #738, but also trying to standardize handling of everything and make placement of token spellings (`AND "and"`) consistently in lexer.lpp.
I could have gone the other direction, removing the list of things in lexer.lpp, but this feels like it does more to use the compiler to detect skew between lexer.lpp and parser.ypp.
Note this makes a few cases where the Statement was optional explicit (Block, If, Sequence). I do add a few CHECKs around where statements were optional and assumed but unverified.
I switch TypeCheckStmt to not take an optional Statement because I think it makes the call sites clearer in behavior. It's also a smaller change than the converse, because taking an optional Statement means the returned statement would also need to be optional. Arguably a wrapper for optional statements could be added, but this still seems cleaner to me, and there aren't that many cases of an optional statement.
Co-authored-by: Geoff Romer <gromer@google.com>
