[AST] Clean up CaptureListEntry

Don't store a VarDecl separately, expose a `getVar`
accessor that forwards onto `getSingleVar`, and
rename `Init` to `PBD`.

Author: hamishknight

include/swift/AST/Expr.h

@@ -4180,13 +4180,11 @@ class AutoClosureExpr : public AbstractClosureExpr {
 /// Instances of this structure represent elements of the capture list that can
 /// optionally occur in a capture expression.
 struct CaptureListEntry {
-  VarDecl *Var;
-  PatternBindingDecl *Init;
+  PatternBindingDecl *PBD;
 
-  CaptureListEntry(VarDecl *Var, PatternBindingDecl *Init)
-  : Var(Var), Init(Init) {
-  }
+  explicit CaptureListEntry(PatternBindingDecl *PBD);
 
+  VarDecl *getVar() const;
   bool isSimpleSelfCapture() const;
 };
 

lib/AST/ASTDumper.cpp

@@ -2496,8 +2496,7 @@ class PrintExpr : public ExprVisitor<PrintExpr> {
     for (auto capture : E->getCaptureList()) {
       OS << '\n';
       Indent += 2;
-      printRec(capture.Var);
-      printRec(capture.Init);
+      printRec(capture.PBD);
       Indent -= 2;
     }
     printRec(E->getClosureBody());

lib/AST/ASTScopeLookup.cpp

@@ -408,7 +408,7 @@ bool PatternEntryInitializerScope::lookupLocalsOrMembers(
 
 bool CaptureListScope::lookupLocalsOrMembers(DeclConsumer consumer) const {
   for (auto &e : expr->getCaptureList()) {
-    if (consumer.consume({e.Var}))
+    if (consumer.consume({e.getVar()}))
       return true;
   }
   return false;

lib/AST/ASTWalker.cpp

@@ -796,16 +796,14 @@ class Traversal : public ASTVisitor<Traversal, Expr*, Stmt*,
   Expr *visitCaptureListExpr(CaptureListExpr *expr) {
     for (auto c : expr->getCaptureList()) {
       if (Walker.shouldWalkCaptureInitializerExpressions()) {
-        for (auto entryIdx : range(c.Init->getNumPatternEntries())) {
-          if (auto newInit = doIt(c.Init->getInit(entryIdx)))
-            c.Init->setInit(entryIdx, newInit);
+        for (auto entryIdx : range(c.PBD->getNumPatternEntries())) {
+          if (auto newInit = doIt(c.PBD->getInit(entryIdx)))
+            c.PBD->setInit(entryIdx, newInit);
           else
             return nullptr;
         }
       } else {
-        // Note we do not walk c.Var here, as it'll be visited as a part of the
-        // PatternBindingDecl.
-        if (doIt(c.Init))
+        if (doIt(c.PBD))
           return nullptr;
       }
     }

lib/AST/Expr.cpp

@@ -1229,7 +1229,18 @@ UnresolvedSpecializeExpr *UnresolvedSpecializeExpr::create(ASTContext &ctx,
                                              UnresolvedParams, RAngleLoc);
 }
 
+CaptureListEntry::CaptureListEntry(PatternBindingDecl *PBD) : PBD(PBD) {
+  assert(PBD);
+  assert(PBD->getSingleVar() &&
+         "Capture lists only support single-var patterns");
+}
+
+VarDecl *CaptureListEntry::getVar() const {
+  return PBD->getSingleVar();
+}
+
 bool CaptureListEntry::isSimpleSelfCapture() const {
+  auto *Var = getVar();
   auto &ctx = Var->getASTContext();
 
   if (Var->getName() != ctx.Id_self)
@@ -1239,10 +1250,10 @@ bool CaptureListEntry::isSimpleSelfCapture() const {
     if (attr->get() == ReferenceOwnership::Weak)
       return false;
 
-  if (Init->getPatternList().size() != 1)
+  if (PBD->getPatternList().size() != 1)
     return false;
 
-  auto *expr = Init->getInit(0);
+  auto *expr = PBD->getInit(0);
 
   if (auto *DRE = dyn_cast<DeclRefExpr>(expr)) {
     if (auto *VD = dyn_cast<VarDecl>(DRE->getDecl())) {
@@ -1265,7 +1276,7 @@ CaptureListExpr *CaptureListExpr::create(ASTContext &ctx,
   auto *expr = ::new(mem) CaptureListExpr(captureList, closureBody);
 
   for (auto capture : captureList)
-    capture.Var->setParentCaptureList(expr);
+    capture.getVar()->setParentCaptureList(expr);
 
   return expr;
 }

lib/IDE/Formatting.cpp

@@ -2586,18 +2586,17 @@ class FormatWalker : public ASTWalker {
 
         ListAligner Aligner(SM, TargetLocation, ContextLoc, L, R);
         for (auto &Entry: ParentCapture->getCaptureList()) {
-          if (auto *PBD = Entry.Init) {
-            NodesToSkip.insert(PBD);
-            SourceRange Range = PBD->getSourceRangeIncludingAttrs();
-            Aligner.updateAlignment(Range, PBD);
+          auto *PBD = Entry.PBD;
+          NodesToSkip.insert(PBD);
+          SourceRange Range = PBD->getSourceRangeIncludingAttrs();
+          Aligner.updateAlignment(Range, PBD);
 
-            if (isTargetContext(Range)) {
-              Aligner.setAlignmentIfNeeded(CtxOverride);
-              return IndentContext {
-                Range.Start,
-                !OutdentChecker::hasOutdent(SM, Range, PBD)
-              };
-            }
+          if (isTargetContext(Range)) {
+            Aligner.setAlignmentIfNeeded(CtxOverride);
+            return IndentContext {
+              Range.Start,
+              !OutdentChecker::hasOutdent(SM, Range, PBD)
+            };
           }
         }
         return Aligner.getContextAndSetAlignment(CtxOverride);

lib/Parse/ParseExpr.cpp

@@ -2651,7 +2651,7 @@ ParserStatus Parser::parseClosureSignatureIfPresent(
           /*VarLoc*/ nameLoc, pattern, /*EqualLoc*/ equalLoc, initializer,
           CurDeclContext);
 
-      auto CLE = CaptureListEntry(VD, PBD);
+      auto CLE = CaptureListEntry(PBD);
       if (CLE.isSimpleSelfCapture())
         VD->setIsSelfParamCapture();
 

lib/SILGen/SILGenExpr.cpp

@@ -1569,7 +1569,7 @@ ManagedValue emitCFunctionPointer(SILGenFunction &SGF,
     DebugScope scope(SGF, CleanupLocation(captureList));
     // CaptureListExprs evaluate their bound variables.
     for (auto capture : captureList->getCaptureList())
-      SGF.visit(capture.Init);
+      SGF.visit(capture.PBD);
 
     // Emit the closure body.
     auto *closure = captureList->getClosureBody();
@@ -2417,7 +2417,7 @@ RValue RValueEmitter::visitCaptureListExpr(CaptureListExpr *E, SGFContext C) {
   DebugScope scope(SGF, CleanupLocation(E));
   // CaptureListExprs evaluate their bound variables.
   for (auto capture : E->getCaptureList())
-    SGF.visit(capture.Init);
+    SGF.visit(capture.PBD);
 
   // Then they evaluate to their body.
   return visit(E->getClosureBody(), C);

lib/Sema/CSApply.cpp

@@ -8108,7 +8108,7 @@ namespace {
       if (auto captureList = dyn_cast<CaptureListExpr>(expr)) {
         // Rewrite captures.
         for (const auto &capture : captureList->getCaptureList()) {
-          (void)rewriteTarget(SolutionApplicationTarget(capture.Init));
+          (void)rewriteTarget(SolutionApplicationTarget(capture.PBD));
         }
       }
 

lib/Sema/CSGen.cpp

@@ -3469,7 +3469,7 @@ namespace {
 
         auto &CS = CG.getConstraintSystem();
         for (const auto &capture : captureList->getCaptureList()) {
-          SolutionApplicationTarget target(capture.Init);
+          SolutionApplicationTarget target(capture.PBD);
           if (CS.generateConstraints(target, FreeTypeVariableBinding::Disallow))
             return {false, nullptr};
         }