Handle subscripts in formDeclNameRef()

In particular, we were unconditionally dropping argument labels on accessors; now we only do that for property accessors, not subscript accessors.

Doing this unconditionally causes ClangImporter failures when a method parameter is called “subscript” (really!), so this behavior is enabled only by the caller’s request.

Author: beccadax

include/swift/Parse/Parser.h

@@ -1822,10 +1822,10 @@ struct ParsedDeclName {
   }
 
   /// Form a declaration name from this parsed declaration name.
-  DeclName formDeclName(ASTContext &ctx) const;
+  DeclName formDeclName(ASTContext &ctx, bool isSubscript = false) const;
 
   /// Form a declaration name from this parsed declaration name.
-  DeclNameRef formDeclNameRef(ASTContext &ctx) const;
+  DeclNameRef formDeclNameRef(ASTContext &ctx, bool isSubscript = false) const;
 };
 
 /// To assist debugging parser crashes, tell us the location of the
@@ -1846,14 +1846,16 @@ DeclName formDeclName(ASTContext &ctx,
                       StringRef baseName,
                       ArrayRef<StringRef> argumentLabels,
                       bool isFunctionName,
-                      bool isInitializer);
+                      bool isInitializer,
+                      bool isSubscript = false);
 
 /// Form a Swift declaration name referemce from its constituent parts.
 DeclNameRef formDeclNameRef(ASTContext &ctx,
                             StringRef baseName,
                             ArrayRef<StringRef> argumentLabels,
                             bool isFunctionName,
-                            bool isInitializer);
+                            bool isInitializer,
+                            bool isSubscript = false);
 
 /// Parse a stringified Swift declaration name, e.g. "init(frame:)".
 DeclName parseDeclName(ASTContext &ctx, StringRef name);

lib/AST/AccessNotes.cpp

@@ -46,14 +46,7 @@ AccessNoteDeclName::AccessNoteDeclName(ASTContext &ctx, StringRef str) {
   else
     accessorKind = None;
 
-  name = parsedName.formDeclName(ctx);
-
-  // FIXME: parseDeclName() doesn't handle the special `subscript` name.
-  // Fixing this without affecting existing uses in import-as-member will need
-  // a bit of work. Hack around the problem for this specific caller instead.
-  if (name.getBaseName() == ctx.getIdentifier("subscript"))
-    name = DeclName(ctx, DeclBaseName::createSubscript(),
-                    name.getArgumentNames());
+  name = parsedName.formDeclName(ctx, /*isSubscript=*/true);
 }
 
 bool AccessNoteDeclName::matches(ValueDecl *VD) const {

lib/Parse/Parser.cpp

@@ -1429,49 +1429,53 @@ ParsedDeclName swift::parseDeclName(StringRef name) {
     }
   } while (!parameters.empty());
 
-  // Drop the argument labels for a property accessor; they aren't used.
-  if (result.isPropertyAccessor())
-    result.ArgumentLabels.clear();
-
   return result;
 }
 
-DeclName ParsedDeclName::formDeclName(ASTContext &ctx) const {
-  return formDeclNameRef(ctx).getFullName();
+DeclName ParsedDeclName::formDeclName(ASTContext &ctx, bool isSubscript) const {
+  return formDeclNameRef(ctx, isSubscript).getFullName();
 }
 
-DeclNameRef ParsedDeclName::formDeclNameRef(ASTContext &ctx) const {
+DeclNameRef ParsedDeclName::formDeclNameRef(ASTContext &ctx,
+                                            bool isSubscript) const {
   return swift::formDeclNameRef(ctx, BaseName, ArgumentLabels, IsFunctionName,
-                                /*IsInitializer=*/true);
+                                /*IsInitializer=*/true, isSubscript);
 }
 
 DeclName swift::formDeclName(ASTContext &ctx,
                              StringRef baseName,
                              ArrayRef<StringRef> argumentLabels,
                              bool isFunctionName,
-                             bool isInitializer) {
+                             bool isInitializer,
+                             bool isSubscript) {
   return formDeclNameRef(ctx, baseName, argumentLabels, isFunctionName,
-                         isInitializer).getFullName();
+                         isInitializer, isSubscript).getFullName();
 }
 
 DeclNameRef swift::formDeclNameRef(ASTContext &ctx,
                                    StringRef baseName,
                                    ArrayRef<StringRef> argumentLabels,
                                    bool isFunctionName,
-                                   bool isInitializer) {
+                                   bool isInitializer,
+                                   bool isSubscript) {
   // We cannot import when the base name is not an identifier.
   if (baseName.empty())
     return DeclNameRef();
   if (!Lexer::isIdentifier(baseName) && !Lexer::isOperator(baseName))
     return DeclNameRef();
 
   // Get the identifier for the base name. Special-case `init`.
-  DeclBaseName baseNameId = ((isInitializer && baseName == "init")
-                             ? DeclBaseName::createConstructor()
-                             : ctx.getIdentifier(baseName));
+  DeclBaseName baseNameId;
+  if (isInitializer && baseName == "init")
+    baseNameId = DeclBaseName::createConstructor();
+  else if (isSubscript && baseName == "subscript")
+    baseNameId = DeclBaseName::createSubscript();
+  else
+    baseNameId = ctx.getIdentifier(baseName);
 
   // For non-functions, just use the base name.
-  if (!isFunctionName) return DeclNameRef(baseNameId);
+  if (!isFunctionName && !baseNameId.isSubscript())
+    return DeclNameRef(baseNameId);
 
   // For functions, we need to form a complete name.