[Diagnostics] Allow failure diagnostic implementation to extend getAnchor

Some of the diagnostics have special rules about anchor location,
let's make `getAnchor` virtual and allow sub-class to override
default implementation.

Author: xedin

lib/Sema/CSDiagnostics.cpp

@@ -864,12 +864,17 @@ bool NoEscapeFuncToTypeConversionFailure::diagnoseParameterUse() const {
   return true;
 }
 
-bool MissingForcedDowncastFailure::diagnoseAsError() {
-  auto *expr = getAnchor();
+Expr *MissingForcedDowncastFailure::getAnchor() const {
+  auto *expr = FailureDiagnostic::getAnchor();
+
   if (auto *assignExpr = dyn_cast<AssignExpr>(expr))
-    expr = assignExpr->getSrc();
+    return assignExpr->getSrc();
 
-  auto *coerceExpr = cast<CoerceExpr>(expr);
+  return expr;
+}
+
+bool MissingForcedDowncastFailure::diagnoseAsError() {
+  auto *coerceExpr = cast<CoerceExpr>(getAnchor());
 
   auto fromType = getFromType();
   auto toType = getToType();
@@ -897,13 +902,21 @@ bool MissingAddressOfFailure::diagnoseAsError() {
   return true;
 }
 
+Expr *MissingExplicitConversionFailure::getAnchor() const {
+  auto *anchor = FailureDiagnostic::getAnchor();
+
+  if (auto *assign = dyn_cast<AssignExpr>(anchor))
+    return assign->getSrc();
+
+  if (auto *paren = dyn_cast<ParenExpr>(anchor))
+    return paren->getSubExpr();
+
+  return anchor;
+}
+
 bool MissingExplicitConversionFailure::diagnoseAsError() {
   auto *DC = getDC();
   auto *anchor = getAnchor();
-  if (auto *assign = dyn_cast<AssignExpr>(anchor))
-    anchor = assign->getSrc();
-  if (auto *paren = dyn_cast<ParenExpr>(anchor))
-    anchor = paren->getSubExpr();
 
   auto fromType = getFromType();
   auto toType = getToType();
@@ -915,9 +928,9 @@ bool MissingExplicitConversionFailure::diagnoseAsError() {
   if (!useAs && !TypeChecker::checkedCastMaySucceed(fromType, toType, DC))
     return false;
 
-  auto *expr = findParentExpr(getAnchor());
+  auto *expr = findParentExpr(anchor);
   if (!expr)
-    expr = getAnchor();
+    expr = anchor;
 
   // If we're performing pattern matching,
   // "as" means something completely different...
@@ -3027,13 +3040,17 @@ bool NonOptionalUnwrapFailure::diagnoseAsError() {
   return true;
 }
 
+Expr *MissingCallFailure::getAnchor() const {
+  auto *anchor = FailureDiagnostic::getAnchor();
+  if (auto *FVE = dyn_cast<ForceValueExpr>(anchor))
+    return FVE->getSubExpr();
+  return anchor;
+}
+
 bool MissingCallFailure::diagnoseAsError() {
   auto *baseExpr = getAnchor();
   SourceLoc insertLoc = baseExpr->getEndLoc();
 
-  if (auto *FVE = dyn_cast<ForceValueExpr>(baseExpr))
-    baseExpr = FVE->getSubExpr();
-
   // Calls are not yet supported by key path, but it
   // is useful to record this fix to diagnose chaining
   // where one of the key path components is a method
@@ -3811,6 +3828,13 @@ bool ImplicitInitOnNonConstMetatypeFailure::diagnoseAsError() {
   return true;
 }
 
+Expr *MissingArgumentsFailure::getAnchor() const {
+  auto *anchor = FailureDiagnostic::getAnchor();
+  if (auto *captureList = dyn_cast<CaptureListExpr>(anchor))
+    return captureList->getClosureBody();
+  return anchor;
+}
+
 bool MissingArgumentsFailure::diagnoseAsError() {
   auto *locator = getLocator();
 
@@ -3827,8 +3851,6 @@ bool MissingArgumentsFailure::diagnoseAsError() {
     return false;
 
   auto *anchor = getAnchor();
-  if (auto *captureList = dyn_cast<CaptureListExpr>(anchor))
-    anchor = captureList->getClosureBody();
 
   if (auto *closure = dyn_cast<ClosureExpr>(anchor))
     return diagnoseClosure(closure);

lib/Sema/CSDiagnostics.h

@@ -81,7 +81,7 @@ class FailureDiagnostic {
 
   Expr *getRawAnchor() const { return RawAnchor; }
 
-  Expr *getAnchor() const { return Anchor; }
+  virtual Expr *getAnchor() const { return Anchor; }
 
   ConstraintLocator *getLocator() const { return Locator; }
 
@@ -779,6 +779,8 @@ class MissingExplicitConversionFailure final : public ContextualFailure {
                                    Type toType, ConstraintLocator *locator)
       : ContextualFailure(solution, fromType, toType, locator) {}
 
+  Expr *getAnchor() const override;
+
   bool diagnoseAsError() override;
 
 private:
@@ -936,6 +938,8 @@ class MissingCallFailure final : public FailureDiagnostic {
   MissingCallFailure(const Solution &solution, ConstraintLocator *locator)
       : FailureDiagnostic(solution, locator) {}
 
+  Expr *getAnchor() const override;
+
   bool diagnoseAsError() override;
 };
 
@@ -1214,6 +1218,8 @@ class MissingArgumentsFailure final : public FailureDiagnostic {
     assert(!SynthesizedArgs.empty() && "No missing arguments?!");
   }
 
+  Expr *getAnchor() const override;
+
   bool diagnoseAsError() override;
 
   bool diagnoseAsNote() override;
@@ -1830,6 +1836,8 @@ class MissingForcedDowncastFailure final : public ContextualFailure {
                                Type toType, ConstraintLocator *locator)
       : ContextualFailure(solution, fromType, toType, locator) {}
 
+  Expr *getAnchor() const override;
+
   bool diagnoseAsError() override;
 };
 

test/Constraints/fixes.swift

@@ -111,7 +111,7 @@ class T {
       // <rdar://problem/17741575>
       let l = self.m2!.prop1
       // expected-error@-1 {{cannot force unwrap value of non-optional type '() -> U?'}} {{22-23=}}
-      // expected-error@-2 {{method 'm2' was used as a property; add () to call it}}  {{23-23=()}}
+      // expected-error@-2 {{method 'm2' was used as a property; add () to call it}}  {{22-22=()}}
     }
 
     func m2() -> U! {