Fix some random compiler warnings

Author: slavapestov

include/swift/AST/PrintOptions.h

@@ -573,12 +573,12 @@ struct PrintOptions {
       QualifyNestedDeclarations::Never;
 
   /// If true, we print a protocol's primary associated types using the
-  /// primary associated type syntax: protocol Foo<Type1, ...>.
+  /// primary associated type syntax: `protocol Foo<Type1, ...>`.
   ///
   /// If false, we print them as ordinary associated types.
   bool PrintPrimaryAssociatedTypes = true;
 
-  /// Whether or not to print \c @attached(extension) attributes on
+  /// Whether or not to print `@attached(extension)` attributes on
   /// macro declarations. This is used for feature suppression in
   /// Swift interface printing.
   bool PrintExtensionMacroAttributes = true;

lib/AST/Module.cpp

@@ -554,6 +554,7 @@ void SourceLookupCache::lookupVisibleDecls(ImportPath::Access AccessPath,
   SmallVector<MissingDecl *, 4> unexpandedDecls;
   for (auto &entry : TopLevelAuxiliaryDecls) {
     for (auto &decl : entry.second) {
+      (void) decl;
       unexpandedDecls.append(entry.second.begin(), entry.second.end());
     }
   }

lib/ConstExtract/ConstExtract.cpp

@@ -815,7 +815,6 @@ void writeParameterizedProtocolSameTypeRequirements(
     llvm::json::OStream &JSON,
     const ParameterizedProtocolType &ParameterizedProtoTy) {
   auto Protocol = ParameterizedProtoTy.getProtocol();
-  auto ProtocolTy = ParameterizedProtoTy.getBaseType();
   auto Requirements = Protocol->getProtocolRequirements();
   auto ParameterTypeNames = Protocol->getPrimaryAssociatedTypeNames();
   auto ProtocolArguments = ParameterizedProtoTy.getArgs();