Remove delayed typo expressions (#143423)

This removes the delayed typo correction functionality from Clang
(regular typo correction still remains) due to fragility of the
solution.

An RFC was posted here:
https://discourse.llvm.org/t/rfc-removing-support-for-delayed-typo-correction/86631
and while that RFC was asking for folks to consider stepping up to be
maintainers, and we did have a few new contributors show some interest,
experiments show that it's likely worth it to remove this functionality
entirely and focus efforts on improving regular typo correction.

This removal fixes ~20 open issues (quite possibly more), improves
compile time performance by roughly .3-.4%
(https://llvm-compile-time-tracker.com/?config=Overview&stat=instructions%3Au&remote=AaronBallman&sortBy=date),
and does not appear to regress diagnostic behavior in a way we wouldn't
find acceptable.

Fixes #142457
Fixes #139913
Fixes #138850
Fixes #137867
Fixes #137860
Fixes #107840
Fixes #93308
Fixes #69470
Fixes #59391
Fixes #58172
Fixes #46215
Fixes #45915
Fixes #45891
Fixes #44490
Fixes #36703
Fixes #32903
Fixes #23312
Fixes #69874

Author: AaronBallman

clang-tools-extra/clangd/unittests/HoverTests.cpp

@@ -974,7 +974,7 @@ class Foo final {})cpp";
          HI.Name = "abc";
          HI.Kind = index::SymbolKind::Variable;
          HI.NamespaceScope = "";
-         HI.Definition = "int abc = <recovery - expr>()";
+         HI.Definition = "int abc";
          HI.Type = "int";
          HI.AccessSpecifier = "public";
        }},

clang/docs/ReleaseNotes.rst

@@ -622,6 +622,14 @@ Improvements to Clang's diagnostics
 
 - Improved the FixIts for unused lambda captures.
 
+- Delayed typo correction was removed from the compiler; immediate typo
+  correction behavior remains the same. Delayed typo correction facilities were
+  fragile and unmaintained, and the removal closed the following issues:
+  #GH142457, #GH139913, #GH138850, #GH137867, #GH137860, #GH107840, #GH93308,
+  #GH69470, #GH59391, #GH58172, #GH46215, #GH45915, #GH45891, #GH44490,
+  #GH36703, #GH32903, #GH23312, #GH69874.
+
+
 Improvements to Clang's time-trace
 ----------------------------------
 

clang/include/clang/AST/Expr.h

@@ -240,8 +240,7 @@ class Expr : public ValueStmt {
     return static_cast<bool>(getDependence() & ExprDependence::UnexpandedPack);
   }
 
-  /// Whether this expression contains subexpressions which had errors, e.g. a
-  /// TypoExpr.
+  /// Whether this expression contains subexpressions which had errors.
   bool containsErrors() const {
     return static_cast<bool>(getDependence() & ExprDependence::Error);
   }
@@ -6965,36 +6964,6 @@ class AtomicExpr : public Expr {
   }
 };
 
-/// TypoExpr - Internal placeholder for expressions where typo correction
-/// still needs to be performed and/or an error diagnostic emitted.
-class TypoExpr : public Expr {
-  // The location for the typo name.
-  SourceLocation TypoLoc;
-
-public:
-  TypoExpr(QualType T, SourceLocation TypoLoc)
-      : Expr(TypoExprClass, T, VK_LValue, OK_Ordinary), TypoLoc(TypoLoc) {
-    assert(T->isDependentType() && "TypoExpr given a non-dependent type");
-    setDependence(ExprDependence::TypeValueInstantiation |
-                  ExprDependence::Error);
-  }
-
-  child_range children() {
-    return child_range(child_iterator(), child_iterator());
-  }
-  const_child_range children() const {
-    return const_child_range(const_child_iterator(), const_child_iterator());
-  }
-
-  SourceLocation getBeginLoc() const LLVM_READONLY { return TypoLoc; }
-  SourceLocation getEndLoc() const LLVM_READONLY { return TypoLoc; }
-
-  static bool classof(const Stmt *T) {
-    return T->getStmtClass() == TypoExprClass;
-  }
-
-};
-
 /// This class represents BOTH the OpenMP Array Section and OpenACC 'subarray',
 /// with a boolean differentiator.
 /// OpenMP 5.0 [2.1.5, Array Sections].

clang/include/clang/AST/RecursiveASTVisitor.h

@@ -2956,7 +2956,6 @@ DEF_TRAVERSE_STMT(CXXRewrittenBinaryOperator, {
   }
 })
 DEF_TRAVERSE_STMT(OpaqueValueExpr, {})
-DEF_TRAVERSE_STMT(TypoExpr, {})
 DEF_TRAVERSE_STMT(RecoveryExpr, {})
 DEF_TRAVERSE_STMT(CUDAKernelCallExpr, {})
 

clang/include/clang/Basic/StmtNodes.td

@@ -202,7 +202,6 @@ def ShuffleVectorExpr : StmtNode<Expr>;
 def ConvertVectorExpr : StmtNode<Expr>;
 def BlockExpr : StmtNode<Expr>;
 def OpaqueValueExpr : StmtNode<Expr>;
-def TypoExpr : StmtNode<Expr>;
 def RecoveryExpr : StmtNode<Expr>;
 def BuiltinBitCastExpr : StmtNode<ExplicitCastExpr>;
 def EmbedExpr : StmtNode<Expr>;

clang/include/clang/Parse/Parser.h

@@ -4169,8 +4169,7 @@ class Parser : public CodeCompletionHandler {
   bool ParseExpressionList(SmallVectorImpl<Expr *> &Exprs,
                            llvm::function_ref<void()> ExpressionStarts =
                                llvm::function_ref<void()>(),
-                           bool FailImmediatelyOnInvalidExpr = false,
-                           bool EarlyTypoCorrection = false);
+                           bool FailImmediatelyOnInvalidExpr = false);
 
   /// ParseSimpleExpressionList - A simple comma-separated list of expressions,
   /// used for misc language extensions.

clang/include/clang/Sema/Sema.h

@@ -6713,10 +6713,6 @@ class Sema final : public SemaBase {
     /// this expression evaluation context.
     unsigned NumCleanupObjects;
 
-    /// The number of typos encountered during this expression evaluation
-    /// context (i.e. the number of TypoExprs created).
-    unsigned NumTypos;
-
     MaybeODRUseExprSet SavedMaybeODRUseExprs;
 
     /// The lambdas that are present within this context, if it
@@ -6813,7 +6809,7 @@ class Sema final : public SemaBase {
                                       Decl *ManglingContextDecl,
                                       ExpressionKind ExprContext)
         : Context(Context), ParentCleanup(ParentCleanup),
-          NumCleanupObjects(NumCleanupObjects), NumTypos(0),
+          NumCleanupObjects(NumCleanupObjects),
           ManglingContextDecl(ManglingContextDecl), ExprContext(ExprContext),
           InDiscardedStatement(false), InImmediateFunctionContext(false),
           InImmediateEscalatingFunctionContext(false) {}
@@ -7146,8 +7142,7 @@ class Sema final : public SemaBase {
                       CorrectionCandidateCallback &CCC,
                       TemplateArgumentListInfo *ExplicitTemplateArgs = nullptr,
                       ArrayRef<Expr *> Args = {},
-                      DeclContext *LookupCtx = nullptr,
-                      TypoExpr **Out = nullptr);
+                      DeclContext *LookupCtx = nullptr);
 
   /// If \p D cannot be odr-used in the current expression evaluation context,
   /// return a reason explaining why. Otherwise, return NOUR_None.
@@ -8748,40 +8743,6 @@ class Sema final : public SemaBase {
 
   ExprResult CheckUnevaluatedOperand(Expr *E);
 
-  /// Process any TypoExprs in the given Expr and its children,
-  /// generating diagnostics as appropriate and returning a new Expr if there
-  /// were typos that were all successfully corrected and ExprError if one or
-  /// more typos could not be corrected.
-  ///
-  /// \param E The Expr to check for TypoExprs.
-  ///
-  /// \param InitDecl A VarDecl to avoid because the Expr being corrected is its
-  /// initializer.
-  ///
-  /// \param RecoverUncorrectedTypos If true, when typo correction fails, it
-  /// will rebuild the given Expr with all TypoExprs degraded to RecoveryExprs.
-  ///
-  /// \param Filter A function applied to a newly rebuilt Expr to determine if
-  /// it is an acceptable/usable result from a single combination of typo
-  /// corrections. As long as the filter returns ExprError, different
-  /// combinations of corrections will be tried until all are exhausted.
-  ExprResult CorrectDelayedTyposInExpr(
-      Expr *E, VarDecl *InitDecl = nullptr,
-      bool RecoverUncorrectedTypos = false,
-      llvm::function_ref<ExprResult(Expr *)> Filter =
-          [](Expr *E) -> ExprResult { return E; });
-
-  ExprResult CorrectDelayedTyposInExpr(
-      ExprResult ER, VarDecl *InitDecl = nullptr,
-      bool RecoverUncorrectedTypos = false,
-      llvm::function_ref<ExprResult(Expr *)> Filter =
-          [](Expr *E) -> ExprResult { return E; }) {
-    return ER.isInvalid()
-               ? ER
-               : CorrectDelayedTyposInExpr(ER.get(), InitDecl,
-                                           RecoverUncorrectedTypos, Filter);
-  }
-
   IfExistsResult
   CheckMicrosoftIfExistsSymbol(Scope *S, CXXScopeSpec &SS,
                                const DeclarationNameInfo &TargetNameInfo);
@@ -9283,12 +9244,6 @@ class Sema final : public SemaBase {
   /// for C++ records.
   llvm::FoldingSet<SpecialMemberOverloadResultEntry> SpecialMemberCache;
 
-  /// Holds TypoExprs that are created from `createDelayedTypo`. This is used by
-  /// `TransformTypos` in order to keep track of any TypoExprs that are created
-  /// recursively during typo correction and wipe them away if the correction
-  /// fails.
-  llvm::SmallVector<TypoExpr *, 2> TypoExprs;
-
   enum class AcceptableKind { Visible, Reachable };
 
   // Members have to be NamespaceDecl* or TranslationUnitDecl*.
@@ -9376,10 +9331,6 @@ class Sema final : public SemaBase {
                       bool VolatileArg, bool RValueThis, bool ConstThis,
                       bool VolatileThis);
 
-  typedef std::function<void(const TypoCorrection &)> TypoDiagnosticGenerator;
-  typedef std::function<ExprResult(Sema &, TypoExpr *, TypoCorrection)>
-      TypoRecoveryCallback;
-
   RedeclarationKind forRedeclarationInCurContext() const;
 
   /// Look up a name, looking for a single declaration.  Return
@@ -9733,51 +9684,6 @@ class Sema final : public SemaBase {
                              const ObjCObjectPointerType *OPT = nullptr,
                              bool RecordFailure = true);
 
-  /// Try to "correct" a typo in the source code by finding
-  /// visible declarations whose names are similar to the name that was
-  /// present in the source code.
-  ///
-  /// \param TypoName the \c DeclarationNameInfo structure that contains
-  /// the name that was present in the source code along with its location.
-  ///
-  /// \param LookupKind the name-lookup criteria used to search for the name.
-  ///
-  /// \param S the scope in which name lookup occurs.
-  ///
-  /// \param SS the nested-name-specifier that precedes the name we're
-  /// looking for, if present.
-  ///
-  /// \param CCC A CorrectionCandidateCallback object that provides further
-  /// validation of typo correction candidates. It also provides flags for
-  /// determining the set of keywords permitted.
-  ///
-  /// \param TDG A TypoDiagnosticGenerator functor that will be used to print
-  /// diagnostics when the actual typo correction is attempted.
-  ///
-  /// \param TRC A TypoRecoveryCallback functor that will be used to build an
-  /// Expr from a typo correction candidate.
-  ///
-  /// \param MemberContext if non-NULL, the context in which to look for
-  /// a member access expression.
-  ///
-  /// \param EnteringContext whether we're entering the context described by
-  /// the nested-name-specifier SS.
-  ///
-  /// \param OPT when non-NULL, the search for visible declarations will
-  /// also walk the protocols in the qualified interfaces of \p OPT.
-  ///
-  /// \returns a new \c TypoExpr that will later be replaced in the AST with an
-  /// Expr representing the result of performing typo correction, or nullptr if
-  /// typo correction is not possible. If nullptr is returned, no diagnostics
-  /// will be emitted and it is the responsibility of the caller to emit any
-  /// that are needed.
-  TypoExpr *CorrectTypoDelayed(
-      const DeclarationNameInfo &Typo, Sema::LookupNameKind LookupKind,
-      Scope *S, CXXScopeSpec *SS, CorrectionCandidateCallback &CCC,
-      TypoDiagnosticGenerator TDG, TypoRecoveryCallback TRC,
-      CorrectTypoKind Mode, DeclContext *MemberContext = nullptr,
-      bool EnteringContext = false, const ObjCObjectPointerType *OPT = nullptr);
-
   /// Kinds of missing import. Note, the values of these enumerators correspond
   /// to %select values in diagnostics.
   enum class MissingImportKind {
@@ -9796,20 +9702,6 @@ class Sema final : public SemaBase {
                              SourceLocation DeclLoc, ArrayRef<Module *> Modules,
                              MissingImportKind MIK, bool Recover);
 
-  struct TypoExprState {
-    std::unique_ptr<TypoCorrectionConsumer> Consumer;
-    TypoDiagnosticGenerator DiagHandler;
-    TypoRecoveryCallback RecoveryHandler;
-    TypoExprState();
-    TypoExprState(TypoExprState &&other) noexcept;
-    TypoExprState &operator=(TypoExprState &&other) noexcept;
-  };
-
-  const TypoExprState &getTypoExprState(TypoExpr *TE) const;
-
-  /// Clears the state of the given TypoExpr.
-  void clearDelayedTypo(TypoExpr *TE);
-
   /// Called on #pragma clang __debug dump II
   void ActOnPragmaDump(Scope *S, SourceLocation Loc, IdentifierInfo *II);
 
@@ -9832,23 +9724,15 @@ class Sema final : public SemaBase {
   /// Determine if we could use all the declarations in the module.
   bool isUsableModule(const Module *M);
 
-  /// Helper for CorrectTypo and CorrectTypoDelayed used to create and
-  /// populate a new TypoCorrectionConsumer. Returns nullptr if typo correction
-  /// should be skipped entirely.
+  /// Helper for CorrectTypo used to create and populate a new
+  /// TypoCorrectionConsumer. Returns nullptr if typo correction should be
+  /// skipped entirely.
   std::unique_ptr<TypoCorrectionConsumer> makeTypoCorrectionConsumer(
       const DeclarationNameInfo &Typo, Sema::LookupNameKind LookupKind,
       Scope *S, CXXScopeSpec *SS, CorrectionCandidateCallback &CCC,
       DeclContext *MemberContext, bool EnteringContext,
       const ObjCObjectPointerType *OPT, bool ErrorRecovery);
 
-  /// The set of unhandled TypoExprs and their associated state.
-  llvm::MapVector<TypoExpr *, TypoExprState> DelayedTypos;
-
-  /// Creates a new TypoExpr AST node.
-  TypoExpr *createDelayedTypo(std::unique_ptr<TypoCorrectionConsumer> TCC,
-                              TypoDiagnosticGenerator TDG,
-                              TypoRecoveryCallback TRC, SourceLocation TypoLoc);
-
   /// Cache for module units which is usable for current module.
   llvm::DenseSet<const Module *> UsableModuleUnitsCache;
 

clang/include/clang/Sema/SemaInternal.h

@@ -314,20 +314,6 @@ class TypoCorrectionConsumer : public VisibleDeclConsumer {
   bool SearchNamespaces;
 };
 
-inline Sema::TypoExprState::TypoExprState() {}
-
-inline Sema::TypoExprState::TypoExprState(TypoExprState &&other) noexcept {
-  *this = std::move(other);
-}
-
-inline Sema::TypoExprState &Sema::TypoExprState::
-operator=(Sema::TypoExprState &&other) noexcept {
-  Consumer = std::move(other.Consumer);
-  DiagHandler = std::move(other.DiagHandler);
-  RecoveryHandler = std::move(other.RecoveryHandler);
-  return *this;
-}
-
 } // end namespace clang
 
 #endif

clang/lib/AST/Expr.cpp

@@ -3611,7 +3611,6 @@ bool Expr::HasSideEffects(const ASTContext &Ctx,
   case PackExpansionExprClass:
   case SubstNonTypeTemplateParmPackExprClass:
   case FunctionParmPackExprClass:
-  case TypoExprClass:
   case RecoveryExprClass:
   case CXXFoldExprClass:
     // Make a conservative assumption for dependent nodes.

clang/lib/AST/ExprClassification.cpp

@@ -129,7 +129,6 @@ static Cl::Kinds ClassifyInternal(ASTContext &Ctx, const Expr *E) {
     // FIXME: Is this wise? Should they get their own kind?
   case Expr::UnresolvedLookupExprClass:
   case Expr::UnresolvedMemberExprClass:
-  case Expr::TypoExprClass:
   case Expr::DependentCoawaitExprClass:
   case Expr::CXXDependentScopeMemberExprClass:
   case Expr::DependentScopeDeclRefExprClass: