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Joe Savona
2ac69bf7d9
This is a start to porting HIRBuilder, with a largely complete implementation of
`build()`. Notably this includes all the passes which build() calls, and the
helper functions those passes call in turn:
```rust
reverse_postorder_blocks(&mut hir);
remove_unreachable_for_updates(&mut hir);
remove_unreachable_fallthroughs(&mut hir);
remove_unreachable_do_while_statements(&mut hir);
mark_instruction_ids(&mut hir)?;
mark_predecessors(&mut hir);
```
This was pretty straightforward. I ran into one borrow checker issue with (iirc)
`remove_unreachable_for_updates` where i needed to simultaneously hold a mutable
reference into the HIR (to write the ForTerminal) and also get an immutable
reference to check if the update block is reachable. The challenge is this:
```rust
for block in hir.blocks.values_mut() {
^^^^^^^^^^^^^^^^^^^^^^^ hir borrowed mutably here
if let TerminalValue::ForTerminal(terminal) = &mut block.terminal.value {
if let Some(update) = terminal.update {
if !hir.blocks.contains(&update) {
^^^^^^^^^^ borrowed immutably here
terminal.update = None;
^^^^^^^^ mutable borrow still active here (and also bc of the loop)
}
}
}
}
```
I quickly worked around this as we do in the other passes here by first building
a set of the block ids contained in the function (so that the
`hir.blocks.contains()` call becomes a call to the copied set of block ids).
An alternative would be to add a helper function for mutable iteration which
takes the desired value out of the data structure so that you can safely mutate
it and reference the rest of the HIR. Usage might look like this:
```rust
hir.blocks.each_mut(|mut block, hir| {
if let TerminalValue::ForTerminal(terminal) = &mut block.terminal.value {
if let Some(update) = terminal.update {
if !hir.blocks.contains(&update) {
terminal.update = None;
}
}
}
})
```
The lambda would receive the current `block` as a mutable reference, and for the
duration of the call `hir.blocks[block.id]` would be set to a sentinel value
that would crash if accessed. Meanwhile, `hir` would be a readonly reference to
the HIR, allowing the lambda to otherwise lookup information on the HIR but not
mutate it. This seems...kinda fine? But also not immediately necessary as
there's an easy and efficient-enough-workaround for the cases i've encountered
so far.
test262
@ 83a46bfe0e
React Forget
React Forget is an experimental Babel plugin to automatically memoize React Hooks and Components.
Development
# tsc --watch
$ yarn dev
# in another terminal window
$ yarn test --watch
Notes
An overview of the implementation can be found in the Architecture Overview.
This transform
- needs plugin-syntax-jsx as a dependency to inherit the syntax from.
- should be run before plugin-transform-react-jsx
- assume the enforcement of rules of hooks, i.e.
- only call hooks from React functions
- only call hooks at the top level
- https://www.npmjs.com/package/eslint-plugin-react-hooks
Scaffolding
- https://github.com/facebook/flow/tree/master/packages/babel-plugin-transform-flow-enums
- https://github.com/babel/babel/blob/main/packages/babel-plugin-transform-react-jsx/src/create-plugin.ts
Reference