handle diags that happen during repl code completion (#24918)

Author: marcrasi

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) {

lib/Sema/TypeCheckREPL.cpp

@@ -286,10 +286,6 @@ void REPLChecker::generatePrintOfExpression(StringRef NameStr, Expr *E) {
 /// When we see an expression in a TopLevelCodeDecl in the REPL, process it,
 /// adding the proper decls back to the top level of the file.
 void REPLChecker::processREPLTopLevelExpr(Expr *E) {
-  // Don't try to print expressions without types.
-  if (!E->getType())
-    return;
-
   CanType T = E->getType()->getCanonicalType();
 
   // Don't try to print invalid expressions, module exprs, or void expressions.

lib/Sema/TypeCheckStmt.cpp

@@ -550,8 +550,7 @@ class StmtChecker : public StmtVisitor<StmtChecker, Stmt*> {
       Type contextType = yieldType;
       if (yieldResults[i].isInOut()) {
         contextTypePurpose = CTP_YieldByReference;
-        if (!contextType->hasError())
-          contextType = LValueType::get(contextType);
+        contextType = LValueType::get(contextType);
 
         // Check that the yielded expression is a &.
         if ((inout = dyn_cast<InOutExpr>(exprToCheck))) {

test/IDE/complete_tf_194.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