[Parse] Check the SourceFile for warning suppression

Move the logic for warning suppression out of the
frontend and into `parseIntoSourceFile`.

Author: hamishknight

lib/Frontend/Frontend.cpp

@@ -970,16 +970,7 @@ void CompilerInstance::parseLibraryFile(
       SourceFileKind::Library, implicitImports.kind, BufferID);
   addAdditionalInitialImportsTo(NextInput, implicitImports);
 
-  auto IsPrimary = isWholeModuleCompilation() || isPrimaryInput(BufferID);
-
-  auto &Diags = NextInput->getASTContext().Diags;
-  auto DidSuppressWarnings = Diags.getSuppressWarnings();
-  Diags.setSuppressWarnings(DidSuppressWarnings || !IsPrimary);
-
   parseIntoSourceFile(*NextInput, BufferID);
-
-  Diags.setSuppressWarnings(DidSuppressWarnings);
-
   performNameBinding(*NextInput);
 }
 

lib/ParseSIL/ParseSIL.cpp

@@ -128,6 +128,15 @@ void swift::parseIntoSourceFile(SourceFile &SF, unsigned int BufferID) {
         SF.SyntaxParsingCache, SF.getASTContext().getSyntaxArena());
   }
 
+  // If we've been asked to silence warnings, do so now. This is needed for
+  // secondary files, which can be parsed multiple times.
+  auto &diags = ctx.Diags;
+  auto didSuppressWarnings = diags.getSuppressWarnings();
+  auto shouldSuppress = SF.getParsingOptions().contains(
+      SourceFile::ParsingFlags::SuppressWarnings);
+  diags.setSuppressWarnings(didSuppressWarnings || shouldSuppress);
+  SWIFT_DEFER { diags.setSuppressWarnings(didSuppressWarnings); };
+
   // If this buffer is for code completion, hook up the state needed by its
   // second pass.
   PersistentParserState *state = nullptr;