Implement backward-compatible closure capture behavior with parser lookup disabled #34135
Conversation
This file contains hidden or bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
|
Note: The large diff is primarily because of the commit that moves preCheckExpression() into it's own file. There are no other changes in that specific commit, so you can review the others individually instead. |
|
@swift-ci Please test source compatibility |
slavapestov
force-pushed
the
simulate-parser-lookup
branch
2 times, most recently
from
7dbfa86 to
330f2e9
Compare
davidungar
approved these changes
Oct 1, 2020
Comment on lines
+670
to
+687
| SmallVector<ValueDecl *, 2> localFuncsAndTypes; | ||
| SmallVector<VarDecl *, 2> localVars; | ||
|
|
||
| // All types and functions are visible anywhere within a brace statement | ||
| // scope. When ordering matters (i.e. var decl) we will have split the brace | ||
| // statement into nested scopes. | ||
| for (auto braceElement : bs->getElements()) { | ||
| if (auto localBinding = braceElement.dyn_cast<Decl *>()) { | ||
| if (auto *vd = dyn_cast<ValueDecl>(localBinding)) { | ||
| if (isa<FuncDecl>(vd) || isa<TypeDecl>(vd)) { | ||
| localFuncsAndTypes.push_back(vd); | ||
| } else if (auto *var = dyn_cast<VarDecl>(localBinding)) { | ||
| localVars.push_back(var); | ||
| } | ||
| } | ||
| } | ||
| } | ||
|
|
lib/AST/ASTScopeLookup.cpp
Outdated
Comment on lines
371
to
380
| if (consumer.consume(localFuncsAndTypes)) | ||
| return true; | ||
|
|
||
| if (consumer.consumePossiblyNotInScope(localVars)) | ||
| return true; | ||
|
|
||
| if (consumer.finishLookupInBraceStmt(stmt)) | ||
| return true; | ||
|
|
||
| return false; |
There was a problem hiding this comment.
Very interesting! Looks good here.
|
@davidungar I split out that change in #34152 |
The parser's own re-declaration checking for local declarations has
slightly different behavior than Sema's re-declaration check.
Whereas Sema rejects this:
class C {
let x = 123
func x() {}
}
The parser accepts this:
func f() {
let x = 123
func x() {}
}
With Sema's check now handling both cases, fudge the behavior to
match the parser in the local case.
…indings when IncludeOuterResults is set The old behavior was that ASTScope would introduce all VarDecls defined in a BraceStmt at the beginning of the BraceStmt. I recently enabled the use of PatternEntryDeclScopes, which introduce the binding at its actual source location instead of at the beginning of the parent statement. This patch now makes use of the new information by having UnqualifiedLookupFlags::IncludeOuterResults toggle between the two behaviors. When searching for outer results, we also consider all VarDecls in a BraceStmt, not just those in scope. This is implemented by giving AbstractASTScopeDeclConsumer a new entry point, consumePossiblyNotInScope(). When looking up into a BraceStmt, all VarDecls are passed in to this entry point. The default implementation does nothing, which means that ASTScope::lookupSingleLocalDecl() now respects source locations when searching for bindings, just like parse-time lookup. However, Sema's preCheckExpression() pass, which sets Flags::IgnoreOuterResults, will continue to find forward-referenced VarDecls, just as it did with the old context-based DeclContext lookup.
slavapestov
force-pushed
the
simulate-parser-lookup
branch
from
330f2e9 to
d219674
Compare
Before performing an UnqualifiedLookup with Flags::IncludeOuterResults turned on, call ASTScope::lookupSingleLocalDecl() to find local bindings that precede the current source location. If this fails, we perform an unqualified lookup to try to find forward references to captures, type members, and top-level declarations.
…clConsumer::consume() It wasn't used for anything, and it was always set based on whether the declaration in question was a GenericTypeParamDecl, a ParamDecl, or something else.
slavapestov
force-pushed
the
simulate-parser-lookup
branch
from
d219674 to
3ec4ced
Compare
|
@swift-ci Please smoke test |
|
@swift-ci Please test source compatibility |
|
Still looks fine! |
|
@slavapestov I think that this change is causing some issues with the latest changes that @hborla did: https://ci-external.swift.org/job/oss-swift-windows-x86_64-vs2019/3047/console shows a couple of test failures (that I also saw on Linux - I don't think that this is Windows specific). |
|
Oops, my bad. Thanks for reverting. I'll take a look. |
Comment on lines
+607
to
+621
| bool ASTScopeDeclConsumerForUnqualifiedLookup::consumePossiblyNotInScope( | ||
| ArrayRef<VarDecl *> vars) { | ||
| if (factory.hasPreciseScopingOfVarDecls()) | ||
| return false; | ||
|
|
||
| for (auto *var : vars) { | ||
| if (!factory.Name.getFullName().isSimpleName(var->getName())) | ||
| continue; | ||
|
|
||
| factory.Results.push_back(LookupResultEntry(var)); | ||
| } | ||
|
|
||
| return false; | ||
| } | ||
|
|
There was a problem hiding this comment.
Was it intentional to always return false here?
Sign up for free
to join this conversation on GitHub.
Already have an account?
Sign in to comment
Add this suggestion to a batch that can be applied as a single commit.
This suggestion is invalid because no changes were made to the code.
Suggestions cannot be applied while the pull request is closed.
Suggestions cannot be applied while viewing a subset of changes.
Only one suggestion per line can be applied in a batch.
Add this suggestion to a batch that can be applied as a single commit.
Applying suggestions on deleted lines is not supported.
You must change the existing code in this line in order to create a valid suggestion.
Outdated suggestions cannot be applied.
This suggestion has been applied or marked resolved.
Suggestions cannot be applied from pending reviews.
Suggestions cannot be applied on multi-line comments.
Suggestions cannot be applied while the pull request is queued to merge.
Suggestion cannot be applied right now. Please check back later.
I wrote about the existing Swift scoping rules for local functions here: https://forums.swift.org/t/clarify-scoping-behavior-with-local-functions/40558
The quick summary is that today, parser lookup runs first, and only finds names that precede the use location in the source file. The old context-based lookup done from
preCheckExpression()finds all local declarations, even those not in scope. A set of heuristics are used to find the relevant local declaration.Since ASTScope has to replace parse-time lookup, it has to model both behaviors. This PR wires it all up.
In the future, we can consider simplifying pre-check's name lookup rules by banning forward references to captured bindings, as I wrote in my forum post. But that's not in the critical path for removing parser lookup anymore.
Builds upon #34125.