Rename startswith to starts_with

LLVM is presumably moving towards `std::string_view` -
`StringRef::startswith` is deprecated on tip. `SmallString::startswith`
was just renamed there (maybe with some small deprecation inbetween, but
if so, we've missed it).

The `SmallString::startswith` references were moved to
`.str().starts_with()`, rather than adding the `starts_with` on
`stable/20230725` as we only had a few of them. Open to switching that
over if anyone feels strongly though.

Author: bnbarham

include/swift/ABI/ObjectFile.h

@@ -60,7 +60,7 @@ class SwiftObjectFileFormatMachO : public SwiftObjectFileFormat {
   }
 
   bool sectionContainsReflectionData(llvm::StringRef sectionName) override {
-    return sectionName.startswith("__swift5_") || sectionName == "__const";
+    return sectionName.starts_with("__swift5_") || sectionName == "__const";
   }
 };
 
@@ -79,7 +79,7 @@ class SwiftObjectFileFormatELF : public SwiftObjectFileFormat {
   }
 
   bool sectionContainsReflectionData(llvm::StringRef sectionName) override {
-    return sectionName.startswith("swift5_");
+    return sectionName.starts_with("swift5_");
   }
 };
 
@@ -98,7 +98,7 @@ class SwiftObjectFileFormatCOFF : public SwiftObjectFileFormat {
   }
 
   bool sectionContainsReflectionData(llvm::StringRef sectionName) override {
-    return sectionName.startswith(".sw5");
+    return sectionName.starts_with(".sw5");
   }
 };
 } // namespace swift

include/swift/APIDigester/ModuleAnalyzerNodes.h

@@ -382,7 +382,7 @@ class SDKNodeDecl: public SDKNode {
   swift::ReferenceOwnership getReferenceOwnership() const {
     return swift::ReferenceOwnership(ReferenceOwnership);
   }
-  bool isObjc() const { return Usr.startswith("c:"); }
+  bool isObjc() const { return Usr.starts_with("c:"); }
   static bool classof(const SDKNode *N);
   DeclKind getDeclKind() const { return DKind; }
   void printFullyQualifiedName(llvm::raw_ostream &OS) const;

include/swift/AST/ASTPrinter.h

@@ -232,7 +232,7 @@ class ASTPrinter {
   void printKeyword(StringRef name,
                     const PrintOptions &Opts,
                     StringRef Suffix = "") {
-    if (Opts.SkipUnderscoredKeywords && name.startswith("_"))
+    if (Opts.SkipUnderscoredKeywords && name.starts_with("_"))
       return;
     assert(!name.empty() && "Tried to print empty keyword");
     callPrintNamePre(PrintNameContext::Keyword);

include/swift/AST/Identifier.h

@@ -174,11 +174,11 @@ class Identifier {
   }
 
   bool hasDollarPrefix() const {
-    return str().startswith("$") && !(getLength() == 1);
+    return str().starts_with("$") && !(getLength() == 1);
   }
 
   bool hasUnderscoredNaming() const {
-    return str().startswith("_");
+    return str().starts_with("_");
   }
 
   const void *getAsOpaquePointer() const {

include/swift/AST/RawComment.h

@@ -57,7 +57,7 @@ struct SingleRawComment {
   }
 
   bool isGyb() const {
-    return RawText.startswith("// ###");
+    return RawText.starts_with("// ###");
   }
 };
 

include/swift/Basic/PathRemapper.h

@@ -53,7 +53,7 @@ class PathRemapper {
     // compatibility with Clang (especially because we propagate the flag to
     // ClangImporter as well).
     for (const auto &Mapping : PathMappings)
-      if (Path.startswith(Mapping.first))
+      if (Path.starts_with(Mapping.first))
         return (Twine(Mapping.second) +
                 Path.substr(Mapping.first.size())).str();
     return Path.str();

include/swift/Basic/PrimitiveParsing.h

@@ -30,7 +30,7 @@ static inline unsigned measureNewline(StringRef S) {
 }
 
 static inline bool startsWithNewline(StringRef S) {
-  return S.startswith("\n") || S.startswith("\r\n");
+  return S.starts_with("\n") || S.starts_with("\r\n");
 }
 
 /// Breaks a given string to lines and trims leading whitespace from them.

include/swift/Demangling/Demangler.h

@@ -415,7 +415,7 @@ class Demangler : public NodeFactory {
   std::function<SymbolicReferenceResolver_t> SymbolicReferenceResolver;
 
   bool nextIf(StringRef str) {
-    if (!Text.substr(Pos).startswith(str)) return false;
+    if (!Text.substr(Pos).starts_with(str)) return false;
     Pos += str.size();
     return true;
   }

include/swift/Parse/Parser.h

@@ -766,7 +766,7 @@ class Parser {
 
   /// Check whether the current token starts with a multi-line string delimiter.
   bool startsWithMultilineStringDelimiter(Token Tok) {
-    return Tok.getText().ltrim('#').startswith("\"\"\"");
+    return Tok.getText().ltrim('#').starts_with("\"\"\"");
   }
 
   /// Returns true if token is an identifier with the given value.

include/swift/Remote/MetadataReader.h

@@ -866,7 +866,7 @@ class MetadataReader {
         StringRef NameStr(Name);
 
         // If this is a Swift-defined protocol, demangle it.
-        if (NameStr.startswith("_TtP")) {
+        if (NameStr.starts_with("_TtP")) {
           auto Demangled = dem.demangleSymbol(NameStr);
           if (!Demangled)
             return resolver.failure();