[Parser] Remove the notion of a "local context".

The "local context" was only used to prevent parsing of closures in a
non-local context, and also string interpolations because they are
similar-ish to closures. However, this isn't something a parser should
decide, so remove this special-case semantic check from the parser and
eliminate the notion of "local context" entirely.

Author: DougGregor

include/swift/Parse/LocalContext.h

@@ -27,7 +27,6 @@
 #include "swift/AST/Stmt.h"
 #include "swift/Basic/OptionSet.h"
 #include "swift/Parse/Lexer.h"
-#include "swift/Parse/LocalContext.h"
 #include "swift/Parse/PersistentParserState.h"
 #include "swift/Parse/Token.h"
 #include "swift/Parse/ParserPosition.h"
@@ -176,8 +175,6 @@ class Parser {
   bool InInactiveClauseEnvironment = false;
   bool InSwiftKeyPath = false;
 
-  LocalContext *CurLocalContext = nullptr;
-
   /// Whether we should delay parsing nominal type, extension, and function
   /// bodies.
   bool isDelayedParsingEnabled() const;
@@ -241,18 +238,15 @@ class Parser {
   protected:
     Parser &P;
     DeclContext *OldContext; // null signals that this has been popped
-    LocalContext *OldLocal;
 
     ContextChange(const ContextChange &) = delete;
     ContextChange &operator=(const ContextChange &) = delete;
 
   public:
-    ContextChange(Parser &P, DeclContext *DC,
-                  LocalContext *newLocal = nullptr)
-      : P(P), OldContext(P.CurDeclContext), OldLocal(P.CurLocalContext) {
+    ContextChange(Parser &P, DeclContext *DC)
+      : P(P), OldContext(P.CurDeclContext) {
       assert(DC && "pushing null context?");
       P.CurDeclContext = DC;
-      P.CurLocalContext = newLocal;
     }
 
     /// Prematurely pop the DeclContext installed by the constructor.
@@ -270,16 +264,15 @@ class Parser {
   private:
     void popImpl() {
       P.CurDeclContext = OldContext;
-      P.CurLocalContext = OldLocal;
     }
   };
 
   /// A RAII object for parsing a new local context.
-  class ParseFunctionBody : public LocalContext {
+  class ParseFunctionBody {
   private:
     ContextChange CC;
   public:
-    ParseFunctionBody(Parser &P, DeclContext *DC) : CC(P, DC, this) {
+    ParseFunctionBody(Parser &P, DeclContext *DC) : CC(P, DC) {
       assert(!isa<TopLevelCodeDecl>(DC) &&
              "top-level code should be parsed using TopLevelCodeContext!");
     }

include/swift/Parse/Parser.h

@@ -18,7 +18,6 @@
 #define SWIFT_PARSE_PERSISTENTPARSERSTATE_H
 
 #include "swift/Basic/SourceLoc.h"
-#include "swift/Parse/LocalContext.h"
 
 namespace swift {
 
@@ -54,9 +53,6 @@ class IDEInspectionDelayedDeclState {
 class PersistentParserState {
   std::unique_ptr<IDEInspectionDelayedDeclState> IDEInspectionDelayedDeclStat;
 
-  /// The local context for all top-level code.
-  TopLevelContext TopLevelCode;
-
 public:
   PersistentParserState();
   PersistentParserState(ASTContext &ctx) : PersistentParserState() { }
@@ -88,10 +84,6 @@ class PersistentParserState {
     assert(hasIDEInspectionDelayedDeclState());
     return std::move(IDEInspectionDelayedDeclStat);
   }
-
-  TopLevelContext &getTopLevelContext() {
-    return TopLevelCode;
-  }
 };
 
 } // end namespace swift

include/swift/Parse/PersistentParserState.h

@@ -4614,7 +4614,7 @@ void Parser::consumeDecl(ParserPosition BeginParserPosition,
 
 void Parser::recordLocalType(TypeDecl *TD) {
   // If we're not in a local context, this is unnecessary.
-  if (!CurLocalContext || !TD->getDeclContext()->isLocalContext())
+  if (!TD->getDeclContext()->isLocalContext())
     return;
 
   if (!InInactiveClauseEnvironment)
@@ -7117,8 +7117,7 @@ Parser::parseDeclVar(ParseDeclOptions Flags,
       Optional<ParseFunctionBody> initParser;
       Optional<ContextChange> topLevelParser;
       if (topLevelDecl)
-        topLevelParser.emplace(*this, topLevelDecl,
-                               &State->getTopLevelContext());
+        topLevelParser.emplace(*this, topLevelDecl);
       if (initContext)
         initParser.emplace(*this, initContext);
 
@@ -7789,16 +7788,7 @@ Parser::parseDeclEnumCase(ParseDeclOptions Flags,
       {
         IDEInspectionCallbacks::InEnumElementRawValueRAII
             InEnumElementRawValue(IDECallbacks);
-        if (!CurLocalContext) {
-          // A local context is needed for parsing closures. We want to parse
-          // them anyways for proper diagnosis.
-          LocalContext tempContext{};
-          CurLocalContext = &tempContext;
-          RawValueExpr = parseExpr(diag::expected_expr_enum_case_raw_value);
-          CurLocalContext = nullptr;
-        } else {
-          RawValueExpr = parseExpr(diag::expected_expr_enum_case_raw_value);
-        }
+        RawValueExpr = parseExpr(diag::expected_expr_enum_case_raw_value);
       }
       if (RawValueExpr.hasCodeCompletion()) {
         Status.setHasCodeCompletionAndIsError();

lib/Parse/ParseDecl.cpp

@@ -2012,15 +2012,6 @@ ParserResult<Expr> Parser::parseExprStringLiteral() {
   // whole InterpolatedStringLiteral.
   llvm::SaveAndRestore<SourceLoc> SavedPreviousLoc(PreviousLoc);
 
-  // We're not in a place where an interpolation would be valid.
-  if (!CurLocalContext) {
-    // Return an error, but include an empty InterpolatedStringLiteralExpr
-    // so that parseDeclPoundDiagnostic() can figure out why this string
-    // literal was bad.
-    return makeParserErrorResult(new (Context) InterpolatedStringLiteralExpr(
-        Loc, Loc.getAdvancedLoc(CloseQuoteBegin), 0, 0, nullptr));
-  }
-
   unsigned LiteralCapacity = 0;
   unsigned InterpolationCount = 0;
   TapExpr * AppendingExpr;
@@ -2778,16 +2769,6 @@ ParserResult<Expr> Parser::parseExprClosure() {
       attributes, bracketRange, captureList, capturedSelfDecl, params, asyncLoc,
       throwsLoc, arrowLoc, explicitResultType, inLoc);
 
-  // If the closure was created in the context of an array type signature's
-  // size expression, there will not be a local context. A parse error will
-  // be reported at the signature's declaration site.
-  if (!CurLocalContext) {
-    skipUntil(tok::r_brace);
-    if (Tok.is(tok::r_brace))
-      consumeToken();
-    return makeParserError();
-  }
-  
   // Create the closure expression and enter its context.
   auto *closure = new (Context) ClosureExpr(
       attributes, bracketRange, capturedSelfDecl, params, asyncLoc, throwsLoc,

lib/Parse/ParseExpr.cpp

@@ -1034,13 +1034,6 @@ ParserResult<Pattern> Parser::parseTypedPattern() {
           !SourceMgr.hasIDEInspectionTargetBuffer()) {
         CancellableBacktrackingScope backtrack(*this);
 
-        // Create a local context if needed so we can parse trailing closures.
-        LocalContext dummyContext;
-        Optional<ContextChange> contextChange;
-        if (!CurLocalContext) {
-          contextChange.emplace(*this, CurDeclContext, &dummyContext);
-        }
-        
         SmallVector<ExprListElt, 2> elts;
         auto argListResult = parseArgumentList(tok::l_paren, tok::r_paren,
                                                /*isExprBasic*/ false);

lib/Parse/ParsePattern.cpp

@@ -396,7 +396,7 @@ ParserStatus Parser::parseBraceItems(SmallVectorImpl<ASTNode> &Entries,
       // If this is a statement or expression at the top level of the module,
       // Parse it as a child of a TopLevelCodeDecl.
       auto *TLCD = new (Context) TopLevelCodeDecl(CurDeclContext);
-      ContextChange CC(*this, TLCD, &State->getTopLevelContext());
+      ContextChange CC(*this, TLCD);
       SourceLoc StartLoc = Tok.getLoc();
 
       // Expressions can't begin with a closure literal at statement position.

lib/Parse/ParseStmt.cpp

@@ -159,7 +159,7 @@ void Parser::performIDEInspectionSecondPassImpl(
     // Re-enter the top-level code decl context.
     // FIXME: this can issue discriminators out-of-order?
     auto *TLCD = cast<TopLevelCodeDecl>(DC);
-    ContextChange CC(*this, TLCD, &State->getTopLevelContext());
+    ContextChange CC(*this, TLCD);
 
     SourceLoc StartLoc = Tok.getLoc();
     ASTNode Result;

lib/Parse/Parser.cpp

@@ -243,9 +243,7 @@ Expr *swift::expandMacroExpr(
 
   // Set up a "local context" for parsing, so that we have a source of
   // closure and local-variable discriminators.
-  LocalContext tempContext{};
   parser.CurDeclContext = dc;
-  parser.CurLocalContext = &tempContext;
 
   auto parsedResult = parser.parseExpr(diag::expected_macro_expansion_expr);
   if (parsedResult.isParseError() || parsedResult.isNull()) {

lib/Sema/TypeCheckMacros.cpp

@@ -40,7 +40,6 @@
 #include "swift/Basic/Statistic.h"
 #include "swift/Basic/TopCollection.h"
 #include "swift/Parse/Lexer.h"
-#include "swift/Parse/LocalContext.h"
 #include "swift/Parse/Parser.h"
 #include "swift/Sema/IDETypeChecking.h"
 #include "llvm/ADT/DenseMap.h"