Fix crash with delayed typo correction

clang/docs/ReleaseNotes.rst

@@ -537,6 +537,9 @@ Improvements to Clang's diagnostics
   constant expression. Prior to this, the error inaccurately implied that assert
   could not be used at all in a constant expression (#GH130458)
 
+- No longer crashing during code generation due to delayed typo correction not
+  causing an unrecoverable error until the end of the translation unit. (#GH140461)
+
 - A new off-by-default warning ``-Wms-bitfield-padding`` has been added to alert to cases where bit-field
   packing may differ under the MS struct ABI (#GH117428).
 

clang/include/clang/Basic/Diagnostic.h

@@ -861,6 +861,18 @@ class DiagnosticsEngine : public RefCountedBase<DiagnosticsEngine> {
 
   bool hasErrorOccurred() const { return ErrorOccurred; }
 
+  /// Sometimes we know an error will be produced at the end of a translation
+  /// unit, such as a delayed typo correction. However, CodeGen is run on each
+  /// top-level decl in an incremental fashion. We don't want CodeGen to run on
+  /// a declaration if an unrecoverable error occurred, but in those cases, the
+  /// error has not yet been emitted. This helper function lets you specify
+  /// that an unrecoverable error will occur later, specifically to ensure that
+  /// CodeGen is not run on those declarations.
+  void setUnrecoverableErrorWillOccur() {
+    UnrecoverableErrorOccurred = true;
+    ErrorOccurred = true;
+  }
+
   /// Errors that actually prevent compilation, not those that are
   /// upgraded from a warning by -Werror.
   bool hasUncompilableErrorOccurred() const {

clang/lib/Sema/SemaLookup.cpp

@@ -5420,6 +5420,13 @@ TypoExpr *Sema::CorrectTypoDelayed(
     TypoDiagnosticGenerator TDG, TypoRecoveryCallback TRC, CorrectTypoKind Mode,
     DeclContext *MemberContext, bool EnteringContext,
     const ObjCObjectPointerType *OPT) {
+
+  // A typo is an unrecoverable diagnostic. However, we sometimes perform code
+  // gen incrementally rather than waiting until the end of the TU, which means
+  // we want to tell the diagnostics engine that an unrecoverable error will
+  // occur eventually.
+  getDiagnostics().setUnrecoverableErrorWillOccur();
+
   auto Consumer = makeTypoCorrectionConsumer(
       TypoName, LookupKind, S, SS, CCC, MemberContext, EnteringContext, OPT,
       Mode == CorrectTypoKind::ErrorRecovery);

clang/test/CodeGenCXX/typo-correction-delayed.cpp

@@ -0,0 +1,11 @@
+// RUN: %clang_cc1 -emit-llvm %s -verify -o /dev/null
+
+// Previously, delayed typo correction would cause a crash because codegen is
+// run on each top-level declaration as we finish with it unless an
+// unrecoverable error occured. However, with delayed typo correction, the
+// error is not emit until the end of the TU, so CodeGen would be run on
+// invalid declarations.
+namespace GH140461 {
+auto s{new auto(one)}; // expected-error {{use of undeclared identifier 'one'}}
+} // namespace GH140461
+