[Parse] Fix a couple typos in PR #12964

Author: graydon

lib/Basic/LangOptions.cpp

@@ -263,7 +263,7 @@ std::pair<bool, bool> LangOptions::setTarget(llvm::Triple triple) {
     addPlatformConditionValue(PlatformConditionKind::Runtime, "_Native");
 
   // Set the "targetEnvironment" platform condition if targeting a simulator
-  // environmet. Otherwise _no_ value is present for targetEnvironment; it's
+  // environment. Otherwise _no_ value is present for targetEnvironment; it's
   // an optional disambiguating refinement of the triple.
   if (swift::tripleIsAnySimulator(Target))
     addPlatformConditionValue(PlatformConditionKind::TargetEnvironment,

lib/Parse/ParseIfConfig.cpp

@@ -550,7 +550,7 @@ static bool isVersionIfConfigCondition(Expr *Condition) {
 /// Get the identifier string from an \c Expr if it's an
 /// \c UnresolvedDeclRefExpr, otherwise the empty string.
 static StringRef getDeclRefStr(Expr *E) {
-  if (auto *UDRE = cast<UnresolvedDeclRefExpr>(E)) {
+  if (auto *UDRE = dyn_cast<UnresolvedDeclRefExpr>(E)) {
     return UDRE->getName().getBaseIdentifier().str();
   }
   return "";