[Diagnostics] Add asNote flag to FailureDiagnostic

The flag is used to indicate that caller is interested in
diagnostic to be a note instead of an error, it's useful
when trying to diagnose ambiguities.

Author: xedin

lib/Sema/CSDiagnostics.cpp

@@ -116,8 +116,8 @@ const DeclContext *RequirementFailure::getRequirementDC() const {
   return AffectedDecl->getAsGenericContext();
 }
 
-bool RequirementFailure::diagnose() {
-  if (!canDiagnoseFailure())
+bool RequirementFailure::diagnose(bool asNote) {
+  if (!canDiagnoseFailure() || asNote)
     return false;
 
   auto *anchor = getAnchor();
@@ -159,8 +159,8 @@ void RequirementFailure::emitRequirementNote(const Decl *anchor) const {
                  req.getFirstType(), getLHS(), req.getSecondType(), getRHS());
 }
 
-bool MissingConformanceFailure::diagnose() {
-  if (!canDiagnoseFailure())
+bool MissingConformanceFailure::diagnose(bool asNote) {
+  if (!canDiagnoseFailure() || asNote)
     return false;
 
   auto *anchor = getAnchor();
@@ -223,15 +223,19 @@ bool MissingConformanceFailure::diagnose() {
   return RequirementFailure::diagnose();
 }
 
-bool LabelingFailure::diagnose() {
+bool LabelingFailure::diagnose(bool asNote) {
   auto &cs = getConstraintSystem();
   auto *call = cast<CallExpr>(getAnchor());
   return diagnoseArgumentLabelError(cs.getASTContext(), call->getArg(),
                                     CorrectLabels,
                                     isa<SubscriptExpr>(call->getFn()));
 }
 
-bool NoEscapeFuncToTypeConversionFailure::diagnose() {
+bool NoEscapeFuncToTypeConversionFailure::diagnose(bool asNote) {
+  // Can't diagnose this problem as a note at the moment.
+  if (asNote)
+    return false;
+
   auto *anchor = getAnchor();
 
   if (ConvertTo) {
@@ -254,8 +258,9 @@ bool NoEscapeFuncToTypeConversionFailure::diagnose() {
   return true;
 }
 
-bool MissingForcedDowncastFailure::diagnose() {
-  if (hasComplexLocator())
+bool MissingForcedDowncastFailure::diagnose(bool asNote) {
+  // Can't diagnose this problem as a note at the moment.
+  if (hasComplexLocator() || asNote)
     return false;
 
   auto &TC = getTypeChecker();
@@ -295,8 +300,9 @@ bool MissingForcedDowncastFailure::diagnose() {
   }
 }
 
-bool MissingAddressOfFailure::diagnose() {
-  if (hasComplexLocator())
+bool MissingAddressOfFailure::diagnose(bool asNote) {
+  // Can't diagnose this problem as a note at the moment.
+  if (hasComplexLocator() || asNote)
     return false;
 
   auto *anchor = getAnchor();
@@ -306,8 +312,9 @@ bool MissingAddressOfFailure::diagnose() {
   return true;
 }
 
-bool MissingExplicitConversionFailure::diagnose() {
-  if (hasComplexLocator())
+bool MissingExplicitConversionFailure::diagnose(bool asNote) {
+  // Can't diagnose this problem as a note at the moment.
+  if (hasComplexLocator() || asNote)
     return false;
 
   auto *DC = getDC();
@@ -363,8 +370,9 @@ bool MissingExplicitConversionFailure::diagnose() {
   return true;
 }
 
-bool MemberAccessOnOptionalBaseFailure::diagnose() {
-  if (hasComplexLocator())
+bool MemberAccessOnOptionalBaseFailure::diagnose(bool asNote) {
+  // Can't diagnose this problem as a note at the moment.
+  if (hasComplexLocator() || asNote)
     return false;
 
   auto *anchor = getAnchor();
@@ -516,8 +524,9 @@ static bool diagnoseUnwrap(ConstraintSystem &CS, Expr *expr, Type type) {
   return true;
 }
 
-bool MissingOptionalUnwrapFailure::diagnose() {
-  if (hasComplexLocator())
+bool MissingOptionalUnwrapFailure::diagnose(bool asNote) {
+  // Can't diagnose this problem as a note at the moment.
+  if (hasComplexLocator() || asNote)
     return false;
 
   auto *anchor = getAnchor();
@@ -533,7 +542,11 @@ bool MissingOptionalUnwrapFailure::diagnose() {
   return true;
 }
 
-bool RValueTreatedAsLValueFailure::diagnose() {
+bool RValueTreatedAsLValueFailure::diagnose(bool asNote) {
+  // Can't diagnose this problem as a note at the moment.
+  if (asNote)
+    return false;
+
   Diag<StringRef> subElementDiagID;
   Diag<Type> rvalueDiagID;
   Expr *diagExpr = getLocator()->getAnchor();

lib/Sema/CSDiagnostics.h

@@ -54,9 +54,12 @@ class FailureDiagnostic {
   /// failure location, types and declarations deduced by
   /// constraint system, and other auxiliary information.
   ///
+  /// \param asNote In ambiguity cases it's beneficial to
+  /// produce diagnostic as a note instead of an error if possible.
+  ///
   /// \returns true If the problem has been successfully diagnosed
   /// and diagnostic message emitted, false otherwise.
-  virtual bool diagnose() = 0;
+  virtual bool diagnose(bool asNote = false) = 0;
 
   ConstraintSystem &getConstraintSystem() const {
     return CS;
@@ -170,7 +173,7 @@ class RequirementFailure : public FailureDiagnostic {
   virtual Type getLHS() const = 0;
   virtual Type getRHS() const = 0;
 
-  bool diagnose() override;
+  bool diagnose(bool asNote = false) override;
 
 protected:
   /// Retrieve declaration contextual where current
@@ -221,7 +224,7 @@ class MissingConformanceFailure final : public RequirementFailure {
       : RequirementFailure(expr, cs, locator),
         NonConformingType(conformance.first), Protocol(conformance.second) {}
 
-  bool diagnose() override;
+  bool diagnose(bool asNote = false) override;
 
 private:
   /// The type which was expected, by one of the generic requirements,
@@ -327,7 +330,7 @@ class LabelingFailure final : public FailureDiagnostic {
                   ArrayRef<Identifier> labels)
       : FailureDiagnostic(nullptr, cs, locator), CorrectLabels(labels) {}
 
-  bool diagnose() override;
+  bool diagnose(bool asNote = false) override;
 };
 
 /// Diagnose errors related to converting function type which
@@ -341,7 +344,7 @@ class NoEscapeFuncToTypeConversionFailure final : public FailureDiagnostic {
                                       Type toType = Type())
       : FailureDiagnostic(expr, cs, locator), ConvertTo(toType) {}
 
-  bool diagnose() override;
+  bool diagnose(bool asNote = false) override;
 };
 
 class MissingForcedDowncastFailure final : public FailureDiagnostic {
@@ -350,7 +353,7 @@ class MissingForcedDowncastFailure final : public FailureDiagnostic {
                                ConstraintLocator *locator)
       : FailureDiagnostic(expr, cs, locator) {}
 
-  bool diagnose() override;
+  bool diagnose(bool asNote = false) override;
 };
 
 /// Diagnose failures related to passing value of some type
@@ -361,7 +364,7 @@ class MissingAddressOfFailure final : public FailureDiagnostic {
                           ConstraintLocator *locator)
       : FailureDiagnostic(expr, cs, locator) {}
 
-  bool diagnose() override;
+  bool diagnose(bool asNote = false) override;
 };
 
 /// Diagnose failures related attempt to implicitly convert types which
@@ -375,7 +378,7 @@ class MissingExplicitConversionFailure final : public FailureDiagnostic {
                                    ConstraintLocator *locator, Type toType)
       : FailureDiagnostic(expr, cs, locator), ConvertingTo(toType) {}
 
-  bool diagnose() override;
+  bool diagnose(bool asNote = false) override;
 
 private:
   bool exprNeedsParensBeforeAddingAs(Expr *expr) {
@@ -416,7 +419,7 @@ class MemberAccessOnOptionalBaseFailure final : public FailureDiagnostic {
       : FailureDiagnostic(expr, cs, locator), Member(memberName),
         ResultTypeIsOptional(resultOptional) {}
 
-  bool diagnose() override;
+  bool diagnose(bool asNote = false) override;
 };
 
 /// Diagnose failures related to use of the unwrapped optional types,
@@ -427,7 +430,7 @@ class MissingOptionalUnwrapFailure final : public FailureDiagnostic {
                                ConstraintLocator *locator)
       : FailureDiagnostic(expr, cs, locator) {}
 
-  bool diagnose() override;
+  bool diagnose(bool asNote = false) override;
 };
 
 /// Diagnose errors associated with rvalues in positions
@@ -438,7 +441,7 @@ class RValueTreatedAsLValueFailure final : public FailureDiagnostic {
   RValueTreatedAsLValueFailure(ConstraintSystem &cs, ConstraintLocator *locator)
       : FailureDiagnostic(nullptr, cs, locator) {}
 
-  bool diagnose() override;
+  bool diagnose(bool asNote = false) override;
 };
 
 } // end namespace constraints