Don't emit an error for code completion

Now that we no longer perform whole-file type
checking for code completion, the ASTVerifier is
no longer expecting fully semantically valid AST.
As such, we no longer need to emit an error to
force it to be more lax with its checks.

Author: hamishknight

include/swift/AST/DiagnosticsFrontend.def

@@ -193,9 +193,6 @@ ERROR(repl_must_be_initialized,none,
       "variables currently must have an initial value when entered at the "
       "top level of the REPL", ())
 
-ERROR(error_doing_code_completion,none,
-      "compiler is in code completion mode (benign diagnostic)", ())
-
 ERROR(verify_encountered_fatal,none,
       "fatal error encountered while in -verify mode", ())
 

lib/Frontend/Frontend.cpp

@@ -822,13 +822,6 @@ void CompilerInstance::parseAndCheckTypesUpTo(
   FrontendStatsTracer tracer(getStatsReporter(), "parse-and-check-types");
 
   bool hadLoadError = parsePartialModulesAndInputFiles();
-  if (Invocation.isCodeCompletion()) {
-    // When we are doing code completion, make sure to emit at least one
-    // diagnostic, so that ASTContext is marked as erroneous.  In this case
-    // various parts of the compiler (for example, AST verifier) have less
-    // strict assumptions about the AST.
-    Diagnostics.diagnose(SourceLoc(), diag::error_doing_code_completion);
-  }
   if (hadLoadError)
     return;
 

tools/SourceKit/lib/SwiftLang/SwiftEditor.cpp

@@ -83,8 +83,7 @@ void EditorDiagConsumer::handleDiagnostic(SourceManager &SM,
   }
 
   // Filter out benign diagnostics for editing.
-  if (Info.ID == diag::lex_editor_placeholder.ID ||
-      Info.ID == diag::error_doing_code_completion.ID)
+  if (Info.ID == diag::lex_editor_placeholder.ID)
     return;
 
   bool IsNote = (Info.Kind == DiagnosticKind::Note);