Merge pull request #17844 from nkcsgexi/rename-back-tracking

libSyntax: rename SyntaxParsingContext.setDiscard() to SyntaxParsingContext.setBackTracking(). NFC

Author: nkcsgexi

include/swift/Parse/Parser.h

@@ -414,7 +414,7 @@ class Parser {
     BacktrackingScope(Parser &P)
         : P(P), PP(P.getParserPosition()), DT(P.Diags) {
       SynContext.emplace(P.SyntaxContext);
-      SynContext->setDiscard();
+      SynContext->setBackTracking();
     }
 
     ~BacktrackingScope();

include/swift/Parse/SyntaxParsingContext.h

@@ -280,8 +280,9 @@ class alignas(1 << SyntaxAlignInBits) SyntaxParsingContext {
   /// Move the collected parts to the tail of parent context.
   void setTransparent() { Mode = AccumulationMode::Transparent; }
 
-  /// Discard collected parts on this context.
-  void setDiscard() { Mode = AccumulationMode::Discard; }
+  /// This context is a back tracking context, so we should discard collected
+  /// parts on this context.
+  void setBackTracking() { Mode = AccumulationMode::Discard; }
 
   /// Explicitly finalizing syntax tree creation.
   /// This function will be called during the destroying of a root syntax

lib/Parse/ParseDecl.cpp

@@ -3546,7 +3546,7 @@ parseDeclTypeAlias(Parser::ParseDeclOptions Flags, DeclAttributes &Attributes) {
   }
 
   if (Flags.contains(PD_InProtocol) && !genericParams && !Tok.is(tok::equal)) {
-    TmpCtxt->setDiscard();
+    TmpCtxt->setBackTracking();
     TmpCtxt.reset();
     // If we're in a protocol and don't see an '=' this looks like leftover Swift 2
     // code intending to be an associatedtype.
@@ -4134,7 +4134,7 @@ bool Parser::parseGetSetImpl(ParseDeclOptions Flags,
       // that the diagnostics point to correct tokens.
       if (BeginParserPosition.isValid()) {
         backtrackToPosition(BeginParserPosition);
-        BacktrackCtxt->setDiscard();
+        BacktrackCtxt->setBackTracking();
         BacktrackCtxt.reset();
         Attributes = DeclAttributes();
       }

lib/Parse/ParseExpr.cpp

@@ -2133,7 +2133,7 @@ DeclName Parser::parseUnqualifiedDeclName(bool afterDot,
     // This is not a compound name.
     // FIXME: Could recover better if we "know" it's a compound name.
     loc = DeclNameLoc(baseNameLoc);
-    ArgsCtxt.setDiscard();
+    ArgsCtxt.setBackTracking();
     return baseName;
   }
   // We have a compound name. Cancel backtracking and build that name.