Support conditional expressions from AST -> HIR -> ReactiveFunction -> AST. This
also helps make the patterns for value block handling more clear, so i was able
to extract some reusable logic in the HIR -> ReactiveFunction conversion phase.
Implements the conversion from LogicalTerminal into a ReactiveLogicalValue (and
ReactiveSequenveValue if necessary). The implementation is a bit rough, i clean
it up in subsequent PRs which revealed parts of the logic that could be shared w
ternaries.
Changes the lowering for LogicalExpression to use the new 'logical' terminal.
Whereas before we tried to more directly model the semantics of `??` by
generating an `if (<lhs> != null)`, we now generate a branch terminal that looks
at the lhs.
The HIR -> ReactiveFunction construction for logical and branch terminals are
placeholders while I refactor the ReactiveFunction representation to support
value blocks.
As discussed, this repurposes OtherStatement as a catch all variant for
unsupported syntax or errors in the source. This also renames the previously
added ErrorTerminal to UnsupportedTerminal for consistency (plus makes it a
little bit less confusing that it's not an actual terminal representing an
Error).
Not loving the name but couldn't think of anything better, open to suggestions!
Previously when converting from HIR -> ReactiveFunction we elided break/continue
terminals in places where control would implicitly transfer to the
break/continue target and therefore nothing has to be emitted. The one downside
of this approach is that it makes scope analysis a bit trickier. We want to
close scopes once we see an instruction id past the end of the scope's range,
but these implicit breaks were causing us to miss some instruction ids. We
compensated for this, but it's helpful to keep the representation explicit and
discard these terminals later in codegen.
Collapses HIRTReeVisitor into BuildReactiveFunction, allowing us to remove the
generic interface and simplify the code. Note that because the visitor was
already not attempting to group instructions by scope anymore, the visitor code
was very straightforward. This is mostly replacing calls to `appendBlock(block,
instr)` with `block.push(instr)`.
The primary goal of this stack is to change HIRTreeVisitor to make it easier to
handle value blocks. That's complicated by the fact that the visitor is a
general-purpose visitor, used in several analysis passes including
BuildReactiveFunction (which translates HIR->ReactiveFunction while also
grouping instructions into scopes) and InferReactiveScopes (which is actually
two passes, one to align scopes to block boundaries, one to merge overlapping
scopes). The long-term goal then is as follows:
1. Make BuildReactiveFunction transform HIR->ReactiveFunction but _without_
reactive scopes.
2. Align scopes to block boundaries, but rewritten to operate on
ReactiveFunction
3. Merge overlapping scopes, again rewritten to operate on ReactiveFunction
4. Group statements within ReactiveFunction into ReactiveScopeBlocks (today this
occurs when constructing the ReactiveFunction).
This PR implements 1 and 4. Because the implementation is incomplete this would
break the whole compiler, so for now both versions are still around. By default
compilation uses the old pipeline, but if a feature flag is enabled we use the
new version. The plan is to incrementally fix up the new version of the passes
in this stack, and then cutover: removing the flag and the old version of the
passes.
Moves _some_ files from HIR into new top-level directories. To not make
@gsathya's life a pain I left the files he's touching alone, but I moved some
others. My intent is to have something like this:
* Babel/ - code for the Babel plugin, though ideally this actually gets split
into a separate package and the compiler itself is AST in, AST out w no Babel
dep.
* HIR/ - the core HIRFunction, HIR and related data types, plus the HIR
construction and printing, HIR visitors.
* Inference/ - the core inference passes that operate on the HIR, including type
inference, reference effects, alias analysis, mutable range analysis, etc. I'll
let @gsathya move these files when at a good stopping point.
* ReactiveScopes/ - inference relating to reactive scopes,
constructing/printing/codegenning ReactiveFunction
* SSA/ - enter/leave SSA and eliminate redundant phis
* Utils/ - every project needs a place to put stuff that doesn't fit into the
other categories, this is ours.
This leaves just index.ts at the top level, and overall feels pretty tidy. Not
too tedious to figure out where anything goes, hopefully.
Joe Savona
Lauren Tan