Move semantic member synthesis into the type checker's lookup utilities

Pull these calls out of lookup itself to prevent re-entrancy.  Synthesizing these members can force a conformance check that can ultimately wind up back in lookup.  Pull the forcing out of every single qualified lookup and just install these members in the TypeChecker's entrypoints to lookup.

The upside is we can localize this gross hack, the downside is, of course, that we have to smear it across all of the lookup entrypoints.

Author: CodaFi

lib/AST/NameLookup.cpp

@@ -1579,34 +1579,6 @@ bool DeclContext::lookupQualified(Type type,
   return lookupQualified(nominalTypesToLookInto, member, options, decls);
 }
 
-static void installPropertyWrapperMembersIfNeeded(NominalTypeDecl *target,
-                                                  DeclName member) {
-  auto &Context = target->getASTContext();
-  auto baseName = member.getBaseName();
-  if (!member.isSimpleName() || baseName.isSpecial())
-    return;
-
-  if ((!baseName.getIdentifier().str().startswith("$") &&
-       !baseName.getIdentifier().str().startswith("_")) ||
-      baseName.getIdentifier().str().size() <= 1) {
-    return;
-  }
-
-  // $- and _-prefixed variables can be generated by properties that have
-  // attached property wrappers.
-  auto originalPropertyName =
-      Context.getIdentifier(baseName.getIdentifier().str().substr(1));
-  for (auto member : target->lookupDirect(originalPropertyName)) {
-    if (auto var = dyn_cast<VarDecl>(member)) {
-      if (var->hasAttachedPropertyWrapper()) {
-        auto sourceFile = var->getDeclContext()->getParentSourceFile();
-        if (sourceFile && sourceFile->Kind != SourceFileKind::Interface)
-          (void)var->getPropertyWrapperBackingProperty();
-      }
-    }
-  }
-}
-
 bool DeclContext::lookupQualified(ArrayRef<NominalTypeDecl *> typeDecls,
                                   DeclName member,
                                   NLOptions options,
@@ -1650,7 +1622,6 @@ bool DeclContext::lookupQualified(ArrayRef<NominalTypeDecl *> typeDecls,
 
   // Visit all of the nominal types we know about, discovering any others
   // we need along the way.
-  auto &ctx = getASTContext();
   bool wantProtocolMembers = (options & NL_ProtocolMembers);
   while (!stack.empty()) {
     auto current = stack.back();
@@ -1659,12 +1630,6 @@ bool DeclContext::lookupQualified(ArrayRef<NominalTypeDecl *> typeDecls,
     if (tracker)
       tracker->addUsedMember({current, member.getBaseName()},isLookupCascading);
 
-    // Make sure we've resolved implicit members, if we need them.
-    if (ctx.areSemanticQueriesEnabled()) {
-      current->synthesizeSemanticMembersIfNeeded(member);
-      installPropertyWrapperMembersIfNeeded(current, member);
-    }
-
     // Look for results within the current nominal type and its extensions.
     bool currentIsProtocol = isa<ProtocolDecl>(current);
     auto flags = OptionSet<NominalTypeDecl::LookupDirectFlags>();

lib/Sema/TypeCheckNameLookup.cpp

@@ -22,6 +22,7 @@
 #include "swift/AST/NameLookup.h"
 #include "swift/AST/NameLookupRequests.h"
 #include "swift/AST/ProtocolConformance.h"
+#include "swift/AST/SourceFile.h"
 #include "swift/Basic/TopCollection.h"
 #include <algorithm>
 
@@ -223,11 +224,47 @@ convertToUnqualifiedLookupOptions(NameLookupOptions options) {
   return newOptions;
 }
 
+static void installPropertyWrapperMembersIfNeeded(NominalTypeDecl *target,
+                                                  DeclName member) {
+  if (!target) return;
+
+  auto &Context = target->getASTContext();
+  auto baseName = member.getBaseName();
+  if (!member.isSimpleName() || baseName.isSpecial())
+    return;
+
+  if ((!baseName.getIdentifier().str().startswith("$") &&
+       !baseName.getIdentifier().str().startswith("_")) ||
+      baseName.getIdentifier().str().size() <= 1) {
+    return;
+  }
+
+  // $- and _-prefixed variables can be generated by properties that have
+  // attached property wrappers.
+  auto originalPropertyName =
+      Context.getIdentifier(baseName.getIdentifier().str().substr(1));
+  for (auto member : target->lookupDirect(originalPropertyName)) {
+    if (auto var = dyn_cast<VarDecl>(member)) {
+      if (var->hasAttachedPropertyWrapper()) {
+        auto sourceFile = var->getDeclContext()->getParentSourceFile();
+        if (sourceFile && sourceFile->Kind != SourceFileKind::Interface)
+          (void)var->getPropertyWrapperBackingProperty();
+      }
+    }
+  }
+}
+
 LookupResult TypeChecker::lookupUnqualified(DeclContext *dc, DeclName name,
                                             SourceLoc loc,
                                             NameLookupOptions options) {
   auto ulOptions = convertToUnqualifiedLookupOptions(options);
 
+  // Make sure we've resolved implicit members, if we need them.
+  if (auto *current = dc->getInnermostTypeContext()) {
+    installPropertyWrapperMembersIfNeeded(current->getSelfNominalTypeDecl(),
+                                          name);
+  }
+
   auto &ctx = dc->getASTContext();
   auto descriptor = UnqualifiedLookupDescriptor(name, dc, loc, ulOptions);
   auto lookup = evaluateOrDefault(ctx.evaluator,
@@ -311,6 +348,12 @@ LookupResult TypeChecker::lookupMember(DeclContext *dc,
   subOptions &= ~NL_RemoveOverridden;
   subOptions &= ~NL_RemoveNonVisible;
 
+  // Make sure we've resolved implicit members, if we need them.
+  if (auto *current = type->getAnyNominal()) {
+    current->synthesizeSemanticMembersIfNeeded(name);
+    installPropertyWrapperMembersIfNeeded(current, name);
+  }
+
   LookupResultBuilder builder(result, dc, options);
   SmallVector<ValueDecl *, 4> lookupResults;
   dc->lookupQualified(type, name, subOptions, lookupResults);
@@ -385,6 +428,12 @@ LookupTypeResult TypeChecker::lookupMemberType(DeclContext *dc,
   if (options.contains(NameLookupFlags::IgnoreAccessControl))
     subOptions |= NL_IgnoreAccessControl;
 
+  // Make sure we've resolved implicit members, if we need them.
+  if (auto *current = type->getAnyNominal()) {
+    current->synthesizeSemanticMembersIfNeeded(name);
+    installPropertyWrapperMembersIfNeeded(current, name);
+  }
+
   if (!dc->lookupQualified(type, name, subOptions, decls))
     return result;