handle diags that happen during repl code completion

Author: Marc Rasi

lib/IDE/REPLCodeCompletion.cpp

@@ -16,6 +16,7 @@
 
 #include "swift/IDE/REPLCodeCompletion.h"
 #include "swift/AST/ASTContext.h"
+#include "swift/AST/DiagnosticSuppression.h"
 #include "swift/AST/Module.h"
 #include "swift/Basic/LLVM.h"
 #include "swift/Basic/SourceManager.h"
@@ -193,7 +194,7 @@ doCodeCompletion(SourceFile &SF, StringRef EnteredCode, unsigned *BufferID,
                  CodeCompletionCallbacksFactory *CompletionCallbacksFactory) {
   // Temporarily disable printing the diagnostics.
   ASTContext &Ctx = SF.getASTContext();
-  DiagnosticTransaction DelayedDiags(Ctx.Diags);
+  DiagnosticSuppression SuppressedDiags(Ctx.Diags);
 
   std::string AugmentedCode = EnteredCode.str();
   AugmentedCode += '\0';
@@ -222,7 +223,10 @@ doCodeCompletion(SourceFile &SF, StringRef EnteredCode, unsigned *BufferID,
   // Now we are done with code completion.  Remove the declarations we
   // temporarily inserted.
   SF.Decls.resize(OriginalDeclCount);
-  DelayedDiags.abort();
+
+  // Reset the error state because it's only relevant to the code that we just
+  // processed, which now gets thrown away.
+  Ctx.Diags.resetHadAnyError();
 }
 
 void REPLCompletions::populate(SourceFile &SF, StringRef EnteredCode) {

test/IDE/repl_complete_with_error.swift

@@ -0,0 +1,8 @@
+// While running completion on this, the typechecker produces a diagnostic and
+// an AST with an error type. If the ASTVerifier ran on the AST with the error
+// type, then it would fail. This test verifies that the ASTVerifier does not
+// run on ASTs with error types produced by completion requests.
+
+// RUN: %target-swift-ide-test -repl-code-completion -source-filename=%s
+
+let bar: NotARealType = 0; ba