[CS] Allow simplification of key path subscript arg locators (#27194)

[CS] Allow simplification of key path subscript arg locators

Author: hamishknight

lib/Sema/CSDiag.cpp

@@ -74,202 +74,6 @@ static bool isUnresolvedOrTypeVarType(Type ty) {
   return ty->isTypeVariableOrMember() || ty->is<UnresolvedType>();
 }
 
-/// Given a subpath of an old locator, compute its summary flags.
-static unsigned recomputeSummaryFlags(ConstraintLocator *oldLocator,
-                                      ArrayRef<LocatorPathElt> path) {
-  if (oldLocator->getSummaryFlags() != 0)
-    return ConstraintLocator::getSummaryFlagsForPath(path);
-  return 0;
-}
-
-ConstraintLocator *
-constraints::simplifyLocator(ConstraintSystem &cs, ConstraintLocator *locator,
-                             SourceRange &range) {
-  auto path = locator->getPath();
-  auto anchor = locator->getAnchor();
-  simplifyLocator(anchor, path, range);
-
-  // If we didn't simplify anything, just return the input.
-  if (anchor == locator->getAnchor() &&
-      path.size() == locator->getPath().size()) {
-    return locator;
-  }
-
-  // Recompute the summary flags if we had any to begin with.  This is
-  // necessary because we might remove e.g. tuple elements from the path.
-  unsigned summaryFlags = recomputeSummaryFlags(locator, path);
-  return cs.getConstraintLocator(anchor, path, summaryFlags);
-}
-
-void constraints::simplifyLocator(Expr *&anchor,
-                                  ArrayRef<LocatorPathElt> &path,
-                                  SourceRange &range) {
-  range = SourceRange();
-
-  while (!path.empty()) {
-    switch (path[0].getKind()) {
-    case ConstraintLocator::ApplyArgument: {
-      // Extract application argument.
-      if (auto applyExpr = dyn_cast<ApplyExpr>(anchor)) {
-        anchor = applyExpr->getArg();
-        path = path.slice(1);
-        continue;
-      }
-
-      if (auto subscriptExpr = dyn_cast<SubscriptExpr>(anchor)) {
-        anchor = subscriptExpr->getIndex();
-        path = path.slice(1);
-        continue;
-      }
-
-      if (auto objectLiteralExpr = dyn_cast<ObjectLiteralExpr>(anchor)) {
-        anchor = objectLiteralExpr->getArg();
-        path = path.slice(1);
-        continue;
-      }
-
-      if (auto *UME = dyn_cast<UnresolvedMemberExpr>(anchor)) {
-        anchor = UME->getArgument();
-        path = path.slice(1);
-        continue;
-      }
-      break;
-    }
-
-    case ConstraintLocator::ApplyFunction:
-      // Extract application function.
-      if (auto applyExpr = dyn_cast<ApplyExpr>(anchor)) {
-        anchor = applyExpr->getFn();
-        path = path.slice(1);
-        continue;
-      }
-
-      // The subscript itself is the function.
-      if (auto subscriptExpr = dyn_cast<SubscriptExpr>(anchor)) {
-        anchor = subscriptExpr;
-        path = path.slice(1);
-        continue;
-      }
-
-      // The unresolved member itself is the function.
-      if (auto unresolvedMember = dyn_cast<UnresolvedMemberExpr>(anchor)) {
-        if (unresolvedMember->getArgument()) {
-          anchor = unresolvedMember;
-          path = path.slice(1);
-          continue;
-        }
-      }
-
-      break;
-
-    case ConstraintLocator::AutoclosureResult:
-    case ConstraintLocator::LValueConversion:
-    case ConstraintLocator::RValueAdjustment:
-    case ConstraintLocator::UnresolvedMember:
-      // Arguments in autoclosure positions, lvalue and rvalue adjustments, and
-      // scalar-to-tuple conversions, and unresolved members are
-      // implicit.
-      path = path.slice(1);
-      continue;
-
-    case ConstraintLocator::NamedTupleElement:
-    case ConstraintLocator::TupleElement: {
-      // Extract tuple element.
-      auto elt = path[0].castTo<LocatorPathElt::AnyTupleElement>();
-      unsigned index = elt.getIndex();
-      if (auto tupleExpr = dyn_cast<TupleExpr>(anchor)) {
-        if (index < tupleExpr->getNumElements()) {
-          anchor = tupleExpr->getElement(index);
-          path = path.slice(1);
-          continue;
-        }
-      }
-
-      if (auto *CE = dyn_cast<CollectionExpr>(anchor)) {
-        if (index < CE->getNumElements()) {
-          anchor = CE->getElement(index);
-          path = path.slice(1);
-          continue;
-        }
-      }
-      break;
-    }
-
-    case ConstraintLocator::ApplyArgToParam: {
-      auto elt = path[0].castTo<LocatorPathElt::ApplyArgToParam>();
-      // Extract tuple element.
-      if (auto tupleExpr = dyn_cast<TupleExpr>(anchor)) {
-        unsigned index = elt.getArgIdx();
-        if (index < tupleExpr->getNumElements()) {
-          anchor = tupleExpr->getElement(index);
-          path = path.slice(1);
-          continue;
-        }
-      }
-
-      // Extract subexpression in parentheses.
-      if (auto parenExpr = dyn_cast<ParenExpr>(anchor)) {
-        assert(elt.getArgIdx() == 0);
-
-        anchor = parenExpr->getSubExpr();
-        path = path.slice(1);
-        continue;
-      }
-      break;
-    }
-    case ConstraintLocator::ConstructorMember:
-      if (auto typeExpr = dyn_cast<TypeExpr>(anchor)) {
-        // This is really an implicit 'init' MemberRef, so point at the base,
-        // i.e. the TypeExpr.
-        range = SourceRange();
-        anchor = typeExpr;
-        path = path.slice(1);
-        continue;
-      }
-      LLVM_FALLTHROUGH;
-
-    case ConstraintLocator::Member:
-    case ConstraintLocator::MemberRefBase:
-      if (auto UDE = dyn_cast<UnresolvedDotExpr>(anchor)) {
-        range = UDE->getNameLoc().getSourceRange();
-        anchor = UDE->getBase();
-        path = path.slice(1);
-        continue;
-      }
-      break;
-
-    case ConstraintLocator::SubscriptMember:
-      if (isa<SubscriptExpr>(anchor)) {
-        path = path.slice(1);
-        continue;
-      }
-      break;
-
-    case ConstraintLocator::ClosureResult:
-      if (auto CE = dyn_cast<ClosureExpr>(anchor)) {
-        if (CE->hasSingleExpressionBody()) {
-          anchor = CE->getSingleExpressionBody();
-          path = path.slice(1);
-          continue;
-        }
-      }
-      break;
-
-    case ConstraintLocator::ContextualType:
-      // This was just for identifying purposes, strip it off.
-      path = path.slice(1);
-      continue;
-
-    default:
-      // FIXME: Lots of other cases to handle.
-      break;
-    }
-
-    // If we get here, we couldn't simplify the path further.
-    break;
-  }
-}
-
 /// Flags that can be used to control name lookup.
 enum TCCFlags {
   /// Allow the result of the subexpression to be an lvalue.  If this is not

lib/Sema/CSDiagnostics.cpp

@@ -2018,8 +2018,10 @@ bool ContextualFailure::diagnoseConversionToNil() const {
       }
 
       // `nil` is passed as an argument to a parameter which doesn't
-      // expect it e.g. `foo(a: nil)` or `s[x: nil]`.
-      if (isa<ApplyExpr>(enclosingExpr) || isa<SubscriptExpr>(enclosingExpr))
+      // expect it e.g. `foo(a: nil)`, `s[x: nil]` or `\S.[x: nil]`.
+      // FIXME: Find a more robust way of checking this.
+      if (isa<ApplyExpr>(enclosingExpr) || isa<SubscriptExpr>(enclosingExpr) ||
+          isa<KeyPathExpr>(enclosingExpr))
         CTP = CTP_CallArgument;
     } else if (auto *CE = dyn_cast<CoerceExpr>(parentExpr)) {
       // `nil` is passed as a left-hand side of the coercion