Add partial support for initializing expressions for variable declaration. This is based on https://github.com/carbon-language/carbon-lang/pull/2006, which introduces expression categories, and how it is possible to convert to/from those different categories.
## Functional changes
* Initializing expressions initialize directly the provided storage when used to initialize a variable.
* Allows initializing expressions to avoid a copy when using `[var|let] name: type = call_expression(...)` by initializing `name` in-place.
* Support `returned var: ...` and `return <expr>`
* Support nested initializing expressions
## Main implementation changes
* Updated PatternMatch logic to handle expression categories
* Updated `VariableDefinition` interpreter statement to allocate and pass a location to initializing expressions
* Update statement actions to allow passing an allocation, used by return expr or returned var
* Modified the RuntimeScope API to be one step closer to the memory model we want to have
* Remove `GetAllocationId` and older `Bind` which don't apply
* New set of tests to highlight those different situations
* Added a new intrinsic to print the allocation stack (and make sure we behave correctly, beyond visible side effects)
## Next work
* Dedicated `Action` to retrieve expression category information in the interpreter (https://github.com/carbon-language/carbon-lang/pull/2927)
* Avoid copies when initializing value expression from reference expression and prevent mutations for the duration of the "pinning" (https://github.com/carbon-language/carbon-lang/pull/2927)
* Avoid unnecessary copies from value expression to value expression, after ensuring that even value expression temporaries are registered for destruction.
* Avoid unnecessary copies when binding function arguments
There are a few implicit conversions that are implemented by an `impl` of `ImplicitAs` that delegates to code in explorer:
- Converting between tuple types
- Converting from tuples of types to `type`
- Converting from tuples of values to an array type
- Converting between struct types
- Converting from a struct type to a class type
These conversions can all rely on performing more conversions for elements or subobjects, but previously those inner conversions could only be performed if they were built into explorer. This change instead uses the full implicit conversion machinery in explorer to perform these conversions, including searching for a user-defined `impl` of `ImplicitAs` when necessary.
For example, this permits a conversion from `{.a: T}` to `{.a: U}`, or from `(T, T)` to `(U, U)`, or from `(T, T)` to `[U; 2]` when there is a user-defined conversion from `T` to `U`.
Depends on #2878
Per #257, we should be treating unformedness as all-or-nothing, rather than being a per-field or per-array-element property. Previously we initialized an array with no explicit initializer as containing a sequence of uninitialized values, but that led to crashes when attempting to access those values, as the checks for reading an uninitialized value only expected values to be uninitialized at the top level.
Also, we had existing tests that attempt to store to an element of an uninitialized array. We now detect that and treat it as UB during evaluation, rather than crashing due to trying to perform field access into an uninitialized value.
Finally, many of these problems can be detected statically, but the resolve_unformed pass wasn't catching them because it missed a few expression and declaration forms. Support for those cases has been added too. This causes the pass to recurse more often, and in particular our existing recursion test started hitting a stack overflow after this, so resolve_unformed now uses `RunWithExtraStack`. In passing, remove the need to explicitly tell `RunWithExtraStack` the return type, and infer it as the return type of the callable instead.
Isolating test execution time (no build time included):
- Linux, `lit` test-per-file: Elapsed time: 28.214s, Critical Path: 13.97s
- Linux, `cc_test`-per-file: Elapsed time: 11.534s, Critical Path: 6.05s
- Linux, merged `cc_test` with 50 shards: Elapsed time: 11.677s, Critical Path: 11.17s
- Mac, `lit` test-per-file: Elapsed time: 295.686s, Critical Path: 20.00s
- Mac, `cc_test`-per-file: Elapsed time: 55.788s, Critical Path: 3.81s
- Mac, merged `cc_test` with 50 shards: Elapsed time: 16.269s, Critical Path: 7.54s
In GH actions:
- [Before](https://github.com/carbon-language/carbon-lang/actions/runs/4866602695/jobs/8678306144?pr=2799):
- test / test (ubuntu-22.04, fastbuild) (pull_request_target) Successful in 20m
- test / test (ubuntu-22.04, opt) (pull_request_target) Successful in 15m
- test / test (macos-12, fastbuild) (pull_request_target) Successful in 36m
- test / test (macos-12, opt) (pull_request_target) Successful in 21m
- [After](https://github.com/carbon-language/carbon-lang/actions/runs/4875154751/jobs/8697004066?pr=2811):
- test / test (ubuntu-22.04, fastbuild) (pull_request_target) Successful in 10m
- test / test (ubuntu-22.04, opt) (pull_request_target) Successful in 9m
- test / test (macos-12, fastbuild) (pull_request_target) Successful in 12m
- test / test (macos-12, opt) (pull_request_target) Successful in 9m
I'm still leaving a handful of `lit` tests to test end-to-end binary execution. This is why testdata directories are split (`lit` tests next to the `explorer` binary, the `cc_test`s next to `ParseAndExecute`).
I couldn't figure out a way to actually hit a reasonable out-of-memory case once I add the maximum interpreter step count. However, the step count limit seems more important.
I've moved the todo stack limit out of function calls because there are plenty of ways to build up the todo stack without any function calls.
Fixes#2791
Removes `__continuation`, `__await`, and `__run`.
In part here, the discussion was that while the feature had been useful for validating the early explorer design, it's no longer needed for that role as the explorer is now quite robust. Continuations have been experimental and, at this point, don't have an owner pushing to a proposal.
The triggering factor is that, as we push to address fuzzer issues, I ran into a crash bug in this code; basically, `fn Main() -> i32 { __await; return 0; }`. When I mentioned this, the reaction seemed to trend towards removal of the feature.
This is adding more validation of intrinsics. It addresses a bug in rand where CHECK-fails would occur for bad range inputs, instead of a runtime error. I'm also addressing what I think was an int32 range issue in the handling by running the generator with int64.
Note the dest_class case didn't actually check dyn_cast success until after using the pointer. That's the case I noticed first, but also cleaning up a couple other small related things.
Move concrete type check for Variable Definition (Local variable) from interpreter to type checker using the `ExpectConcreteType` function created in #2748
Rename value categories to expression categories based on [Discord discussion](https://discord.com/channels/655572317891461132/753021843459538996/1092924035517665332) regarding naming and behavior.
>* let expression -> value expression
>* var expression -> reference expression
>* located expression -> initializing expression
>So:
>- "value expressions" produce values (with no associated location). "reference expressions" produce a location of an existing value. "initializing expressions" take a location and initialize it.
>- A let binding is initialized by a value expression, because lets represent values (with category conversions performed as needed, but if a conversion is performed from a different category of expression, the value of the object is pinned for the lifetime of the let).
>- A var binding is initialized by an initializing expression, without performing a copy (with category conversions performed as needed, calling a copy constructor if the initializer is a different expression category).
>- The & operator requires a reference expression, and it's an error to give it other kinds.
>- The left-hand side of . requires a value expression when calling a function with a non-addr receiver, and requires a reference expression when calling a function with an addr receiver (it's an error to give it a value expression, and for an initializing expression, a temporary is materialized).
Changes
* Rename "value category" to "expression category"
* Rename Var and Let value categories to Value, Reference, and Initializing expression
* Rename `lvalue` to `location` (most of the time)
Added an alternative way of Instantiating types (it was previously done using `InstantiateType` method).
Created an `Action` called `TypeInstantiationAction` and changed most of the code that directly invokes `InstantiateType` to instead spawn a new `TypeInstantiationAction`.
Relates to [#2594 ](https://github.com/carbon-language/carbon-lang/issues/2594)
This PR is making two main changes to the Explorer and Toolchain:
- Replace the `is` keyword in `where SomeType is SomeInterface` with `impls`, so it is `where SomeType impls SomeInterface`
- Rewrite uses of the "impls" to something else to avoid, frequently "`impl` declarations" or "implementations", to avoid confusion with the `impls` keyword.
---------
Co-authored-by: Geoff Romer <gromer@google.com>
The strategy that we use for now to support template instantiation is to check the impl declaration as if it were a generic, but to defer all checking of the impl definition until we see a use in which all template parameters have arguments. At that point, we clone the impl definition and type-check the whole thing, with constant values set on the template parameters corresponding to the given arguments.
No caching of template instantiations is performed yet; each time we form a reference to a template instantiation, we instantiate it afresh. We also don't implement the name lookup rule from #949 yet; lookups during template instantiation look only in the actual type and not in the constraint.
Depends on #2699
### Features
* Add virtual `destructor`s support (Closes#2521)
* Check virtual override for virtual destructors
* Error if attempting to `Delete` a class that does not have virtual destructors from a base class pointer
### Implementation
* Update parser to support virtual override introducers for destructors
* Check virtual override for class destructor and add to class vtable if necessary
* Add corresponding tests
### Notes
Contrary to initial implementation, this implementation leverages the `Address` structure and implements a new `Address::DowncastedAddress()` method to get address from child most class from a base class address. This avoids the need to use `GetAllocationId` and its issues when it comes to having multiple values for an `AllocationId`.
### Next work
Following this PR, we need to:
* Check when using `Delete` that the class was allocated with `New` (WIP)
* Drop the old `GetAllocationId(Value*)` in favor of a better system (WIP)
These are used by the AST in lots of ways, and this resolves various layering issues.
This means that `AllocationId` also lives in ast/, but is managed by interpreter/. A better layering here would be desirable, but this seems good enough for the time being.
This fixes some bugs in each, where the fixes had only been made on one
side of the switch or the other. Also don't forget to instantiate
deduced generic arguments in a call when we read them out of the AST.
This is intended to address currently flaky timeouts that are likely caused by the size of the prelude. I'm addressing a performance bottleneck in AnalyzeProgram with trace output. Trying to omit prelude traces reduces most trace output significantly, and I think it'll scale better as the prelude size increases.
The basic mechanics here are:
- In order to consistently track whether tracing is on, I've added a TraceStream class, explorer/interpreter/trace_stream.h.
- The AST now has a num_prelude_declarations field, so that it's provided where the boundary is.
- In order to mark where we try to skip prelude output, I've added calls to set_in_prelude in type_checker.
- In exec_program, I just use num_prelude_declarations directly to skip over.
- Everywhere checks TraceStream::is_enabled before printing, similar to the std::optional check that was previously used.
This does add some timing output in order to better diagnose where slowness is coming from, when tracing. It also adds "verbose" targets to make it easier to get the trace output.
So for example, here's a timing for zero.carbon:
```
Timings:
- Parse: 13ms
- AddPrelude: 25ms
- AnalyzeProgram: 116ms
- ExecProgram: 12ms
```
If I make a small change to just not set skipping_prelude (essentially getting back to current output):
```
- Parse: 13ms
- AddPrelude: 25ms
- AnalyzeProgram: 2359ms
- ExecProgram: 57ms
```
Thus in this trivial example, I'm eliminating about 95% of the execution time.
Note this approach could still be refined in a few ways:
- We could add a flag to allow overriding in_prelude. It should be a small amount of work after this change. But it's a little consistent with how parser_debug works, that it won't print prelude output by default (unless there's an error).
- Execution could skip messages involving initialization of globals declared in the prelude. This is a little noisy right now, but I don't think it's significant for performance because ExecProgram is tiny.
- Once files are more separated, we should be able to change the num_prelude_declarations/set_in_prelude approach.
Co-authored-by: Richard Smith <richard@metafoo.co.uk>
The design of choice types expects the declaration of an alternative to match the usage: if an alternative is declared as `None`, then it should be used as `None` not `None()`, and if it is declared as `None()` then it should be used as `None()` not `None`. Update explorer to match.
Also clean up the handling of choice types and alternative values a little in general, by moving away from identifying choice types and alternatives as strings and towards identifying them symbolically.
Closes#2422
Return Integer overflow Runtime error for bit shift if The second operand is less than zero or bigger than or equal bit width of the first operand in this case (32 bit for int)
Issue #2595
Name lookup into namespaces needs to be resolved early, as part of name resolution, so that we can properly diagnose references to entities before they are fully declared. Make name resolution set a target `value_node` on simple member accesses that name namespace members, and in type-checking rewrite those member accesses into `IdentifierExpression`s that directly reference the namespace member.
Move deallocation logic to `StepCleanUp` to have all necessary cleanup actions in the same place. Currently this means `DestroyAction` and `heap_.Deallocate`.
Fix variables not being properly cleaned up if declared before an unformed variable.
### Details
Currently the following example / test
```
package ExplorerTest api;
class A {
var i: i32;
destructor[self: Self] {
Print("Destructor A {0}", self.i);
}
}
fn Main() -> i32 {
var a0: A;
var a1: A = {.i = 1};
var a2: A;
var a3: A = {.i = 3};
return 0;
}
```
prints
```
Destructor A 3
```
instead of
```
Destructor A 3
Destructor A 1
```
This PR fixes the issue in the `CleanUp` logic.
Add support for user-defined assignment, as well as compound assignment and increment, following the design direction in pending proposal #2511.
Some of this isn't fully testable yet: because explorer doesn't properly support `impl` specialization, the blanket `impl`s in the prelude prevent types from customizing assignment.
Naming this ToString within the Carbon namespace encourages incidental overloading of the function, and that doesn't seem to be intentional; this feels questionable [under overloading style](https://google.github.io/styleguide/cppguide.html#Function_Overloading). OperatorToString seems helpful in that it makes it easy to see at a glance where it's being used.
Add a check to prevent creating a class from a struct with a missing parent.
This is already type-checked for carbon / user code, but not when using `Convert` manually.
Add a blanket `ImplicitAs` implementation to perform the conversions that explorer can perform as built-in conversions. This allows those conversions to be detected by constraints and to be used as part of other user-defined conversions. For now, a single monolithic conversion is exposed. I intend to split this up into multiple smaller conversion kinds for each kind of conversion in a follow-up change.
Co-authored-by: Jon Ross-Perkins <jperkins@google.com>
Add basic support for `match_first` declarations to explorer, as described in https://github.com/carbon-language/carbon-lang/blob/trunk/docs/design/generics/details.md#prioritization-rule. The concrete syntax here is not yet approved, so `match_first` is renamed to `__match_first` for now, but the semantics are necessary to implement other approved features in explorer so we're intentionally getting a little ahead of the design here.
Currently, only the action class uses the noun case (`Cleanup`), while the kind enum and functions are spelled `CleanUpAction`. Other actions use consistent casing between class and enum names. This change makes the name consistent, and unsurprising for developers. Mirrors `DestroyAction` (verb).
Also make minor updates to the skeletal design in
docs/design/name_lookup.md following #2113, as there are no longer any prelude names that are made available to unqualified name lookup by default.
Add `type` to the keyword list in
docs/design/lexical_conventions/words.md, following #2360.
Features:
* Add `virtual` virtual override keyword for functions
* Support `virtual` class methods using dynamic dispatch
Changes:
* Add `vtable` in `NominalClassType`,
* Add `NominalClassValue**` in class values pointing to descendant-most class
* Resolve virtual methods during member lookup
Limitations:
* Does not include yet `impl`, `abstract` virtual override keywords, or the complete logic for virtual function declaration
Depends on #2460
Relates to #1881
Relates to #2493
Addresses comments from this discussion: https://github.com/carbon-language/carbon-lang/pull/2460#discussion_r1046444433
Features:
* Move subtyping logic from Interpreter to TypeChecker, exposing subtyping as a series of access to `.base`.
* Excludes function parameter conversion, which is still done in ::Convert due to parameters conversion being handled differently.
Changes:
* Add new `class BaseAccessExpression : public MemberAccessExpression`, allowing rewrites
* Handle `BaseAccessExpression` expression type in Interpreter
* Move subtyping logic to `TypeChecker::ImplicitlyConvert`
Add a generic mechanism to decompose a `Value` and rebuild it, and use that to implement `Substitute`'s recursive transformation of values instead of a hand-rolled decomposition. This means `Substitute` now covers all kinds of values, whereas previously it used to be unable to transform some values, and should be less work to add new kinds of value.
We can use the same mechanism for various other things: structural dumping of values, equality comparisons, and value instantiation in the interpreter would all benefit from this. But in this change I'm just switching `Substitute` to this as a first step.
Depends on #2361, #2421
Add support for destructors of base classes.
Features:
- Call destructors from derived to base class
- Support addressing `TupleValue` using a new `Member` variant
Changes:
- Update `StepDestroy()` to recursively call destructors from derived to base class
- Add new `Member` variant and `IndexedValue` struct to be usable with `TupleValue`
Jon Ross-Perkins
Adrien Leravat
josh11b
Geoff Romer
Richard Smith
kshokhin
Amr Hesham
Poorna Gunathilaka
Prabhat Sachdeva