[3.1] Improve compile-time performance of string interpolation

lib/Sema/CSApply.cpp

@@ -2099,45 +2099,32 @@ namespace {
       // Create a tuple containing all of the segments.
       SmallVector<Expr *, 4> segments;
       SmallVector<Identifier, 4> names;
-      unsigned index = 0;
       ConstraintLocatorBuilder locatorBuilder(cs.getConstraintLocator(expr));
       for (auto segment : expr->getSegments()) {
-        auto locator = cs.getConstraintLocator(
-                      locatorBuilder.withPathElement(
-                          LocatorPathElt::getInterpolationArgument(index++)));
-
-        // Find the initializer we chose.
-        auto choice = getOverloadChoice(locator);
-
-        auto memberRef = buildMemberRef(
-                           typeRef, choice.openedFullType,
-                           segment->getStartLoc(), choice.choice.getDecl(),
-                           DeclNameLoc(segment->getStartLoc()),
-                           choice.openedType,
-                           locator, locator, /*Implicit=*/true,
-                           choice.choice.getFunctionRefKind(),
-                           AccessSemantics::Ordinary,
-                           /*isDynamic=*/false);
         ApplyExpr *apply =
           CallExpr::createImplicit(
-            tc.Context, memberRef,
+            tc.Context, typeRef,
             { segment },
             { tc.Context.Id_stringInterpolationSegment });
         cs.cacheType(apply->getArg());
 
-        auto converted = finishApply(apply, openedType, locatorBuilder);
-        if (!converted)
-          return nullptr;
+        Expr *convertedSegment = apply;
+        if (tc.typeCheckExpressionShallow(convertedSegment, cs.DC))
+          continue;
 
-        segments.push_back(converted);
+        segments.push_back(convertedSegment);
 
-        if (index == 1) {
+        if (names.empty()) {
           names.push_back(tc.Context.Id_stringInterpolation);
         } else {
           names.push_back(Identifier());
         }
       }
 
+      // If all of the segments had errors, bail out.
+      if (segments.empty())
+        return nullptr;
+
       // Call the init(stringInterpolation:) initializer with the arguments.
       ApplyExpr *apply = CallExpr::createImplicit(tc.Context, memberRef,
                                                   segments, names);
@@ -4115,22 +4102,7 @@ findCalleeDeclRef(ConstraintSystem &cs, const Solution &solution,
 
     unsigned newFlags = locator->getSummaryFlags();
 
-    // If we have an interpolation argument, dig out the constructor if we
-    // can.
-    // FIXME: This representation is actually quite awful
-    if (newPath.size() == 1 &&
-        newPath[0].getKind() == ConstraintLocator::InterpolationArgument) {
-      newPath.push_back(ConstraintLocator::ConstructorMember);
-
-      locator = cs.getConstraintLocator(locator->getAnchor(), newPath, newFlags);
-      auto known = solution.overloadChoices.find(locator);
-      if (known != solution.overloadChoices.end()) {
-        auto &choice = known->second.choice;
-        if (choice.getKind() == OverloadChoiceKind::Decl)
-          return cast<AbstractFunctionDecl>(choice.getDecl());
-      }
-      return nullptr;
-    } else if (isSubscript) {
+    if (isSubscript) {
       newPath.push_back(ConstraintLocator::SubscriptMember);
     } else {
       newPath.push_back(ConstraintLocator::ApplyFunction);

lib/Sema/CSDiag.cpp

@@ -222,22 +222,6 @@ void constraints::simplifyLocator(Expr *&anchor,
       }
       break;
 
-    case ConstraintLocator::InterpolationArgument:
-      if (auto interp = dyn_cast<InterpolatedStringLiteralExpr>(anchor)) {
-        unsigned index = path[0].getValue();
-        if (index < interp->getSegments().size()) {
-          // No additional target locator information.
-          // FIXME: Dig out the constructor we're trying to call?
-          targetAnchor = nullptr;
-          targetPath.clear();
-
-          anchor = interp->getSegments()[index];
-          path = path.slice(1);
-          continue;
-        }
-      }
-      break;
-
     case ConstraintLocator::SubscriptIndex:
       if (auto subscript = dyn_cast<SubscriptExpr>(anchor)) {
         targetAnchor = subscript->getBase();

lib/Sema/CSGen.cpp

@@ -1022,6 +1022,16 @@ namespace {
     DeclContext *CurDC;
     SmallVector<DeclContext*, 4> DCStack;
 
+    static const unsigned numEditorPlaceholderVariables = 2;
+
+    /// A buffer of type variables used for editor placeholders. We only
+    /// use a small number of these (rotating through), to prevent expressions
+    /// with a large number of editor placeholders from flooding the constraint
+    /// system with type variables.
+    TypeVariableType *editorPlaceholderVariables[numEditorPlaceholderVariables]
+      = { nullptr, nullptr };
+    unsigned currentEditorPlaceholderVariable = 0;
+
     /// \brief Add constraints for a reference to a named member of the given
     /// base type, and return the type of such a reference.
     Type addMemberRefConstraints(Expr *expr, Expr *base, DeclName name,
@@ -1224,7 +1234,6 @@ namespace {
     visitInterpolatedStringLiteralExpr(InterpolatedStringLiteralExpr *expr) {
       // Dig out the ExpressibleByStringInterpolation protocol.
       auto &tc = CS.getTypeChecker();
-      auto &C = CS.getASTContext();
       auto interpolationProto
         = tc.getProtocol(expr->getLoc(),
                          KnownProtocolKind::ExpressibleByStringInterpolation);
@@ -1241,26 +1250,6 @@ namespace {
                        interpolationProto->getDeclaredType(),
                        locator);
 
-      // Each of the segments is passed as an argument to
-      // init(stringInterpolationSegment:).
-      unsigned index = 0;
-      auto tvMeta = MetatypeType::get(tv);
-      for (auto segment : expr->getSegments()) {
-        auto locator = CS.getConstraintLocator(
-                         expr,
-                         LocatorPathElt::getInterpolationArgument(index++));
-        auto segmentTyV = CS.createTypeVariable(locator, /*options=*/0);
-        auto returnTyV = CS.createTypeVariable(locator, /*options=*/0);
-        auto methodTy = FunctionType::get(segmentTyV, returnTyV);
-
-        CS.addConstraint(ConstraintKind::Conversion, CS.getType(segment),
-                         segmentTyV, locator);
-
-        DeclName segmentName(C, C.Id_init, { C.Id_stringInterpolationSegment });
-        CS.addValueMemberConstraint(tvMeta, segmentName, methodTy, CurDC,
-                                    FunctionRefKind::DoubleApply, locator);
-      }
-
       return tv;
     }
 
@@ -2760,14 +2749,28 @@ namespace {
     Type visitEditorPlaceholderExpr(EditorPlaceholderExpr *E) {
       if (E->getTypeLoc().isNull()) {
         auto locator = CS.getConstraintLocator(E);
-        auto placeholderTy = CS.createTypeVariable(locator, /*options*/0);
+
         // A placeholder may have any type, but default to Void type if
         // otherwise unconstrained.
-        CS.addConstraint(ConstraintKind::Defaultable,
-                         placeholderTy, TupleType::getEmpty(CS.getASTContext()),
-                         locator);
+        auto &placeholderTy
+          = editorPlaceholderVariables[currentEditorPlaceholderVariable];
+        if (!placeholderTy) {
+          placeholderTy = CS.createTypeVariable(locator, /*options*/0);
+
+          CS.addConstraint(ConstraintKind::Defaultable,
+                           placeholderTy,
+                           TupleType::getEmpty(CS.getASTContext()),
+                           locator);
+        }
+
+        // Move to the next placeholder variable.
+        currentEditorPlaceholderVariable
+          = (currentEditorPlaceholderVariable + 1) %
+              numEditorPlaceholderVariables;
+
         return placeholderTy;
       }
+
       // NOTE: The type loc may be there but have failed to validate, in which
       // case we return the null type.
       return E->getType();

lib/Sema/CSSolver.cpp

@@ -2465,17 +2465,6 @@ bool ConstraintSystem::solveSimplified(
         if (*restriction == ConversionRestrictionKind::TupleToTuple)
           break;
       }
-
-      // Or, if we see a conversion successfully applied to a string
-      // interpolation argument, we're done.
-      // FIXME: Probably should be more general, as mentioned above.
-      if (auto locator = disjunction->getLocator()) {
-        if (!locator->getPath().empty() &&
-            locator->getPath().back().getKind()
-              == ConstraintLocator::InterpolationArgument &&
-            constraint->getKind() == ConstraintKind::Conversion)
-          break;
-      }
     }
 
     if (TC.getLangOpts().DebugConstraintSolver) {

lib/Sema/ConstraintLocator.cpp

@@ -70,7 +70,6 @@ void ConstraintLocator::Profile(llvm::FoldingSetNodeID &id, Expr *anchor,
     case ScalarToTuple:
     case Load:
     case GenericArgument:
-    case InterpolationArgument:
     case NamedTupleElement:
     case TupleElement:
     case ApplyArgToParam:
@@ -164,10 +163,6 @@ void ConstraintLocator::dump(SourceManager *sm, raw_ostream &out) {
       out << "instance type";
       break;
 
-    case InterpolationArgument:
-      out << "interpolation argument #" << llvm::utostr(elt.getValue());
-      break;
-
     case Load:
       out << "load";
       break;

lib/Sema/ConstraintLocator.h

@@ -91,8 +91,6 @@ class ConstraintLocator : public llvm::FoldingSetNode {
     SubscriptIndex,
     /// \brief The result of a subscript expression.
     SubscriptResult,
-    /// \brief An argument to string interpolation.
-    InterpolationArgument,
     /// \brief The lookup for a constructor member.
     ConstructorMember,
     /// \brief Rvalue adjustment.
@@ -155,7 +153,6 @@ class ConstraintLocator : public llvm::FoldingSetNode {
       return 0;
 
     case GenericArgument:
-    case InterpolationArgument:
     case NamedTupleElement:
     case TupleElement:
       return 1;
@@ -204,7 +201,6 @@ class ConstraintLocator : public llvm::FoldingSetNode {
     case Archetype:
     case AssociatedType:
     case GenericArgument:
-    case InterpolationArgument:
     case NamedTupleElement:
     case TupleElement:
     case Requirement:
@@ -335,12 +331,6 @@ class ConstraintLocator : public llvm::FoldingSetNode {
       return PathElement(GenericArgument, position);
     }
 
-    /// \brief Retrieve a path element for an argument to string
-    /// interpolation.
-    static PathElement getInterpolationArgument(unsigned position) {
-      return PathElement(InterpolationArgument, position);
-    }
-
     /// \brief Retrieve the kind of path element.
     PathElementKind getKind() const {
       switch (static_cast<StoredKind>(storedKind)) {

stdlib/public/core/StringInterpolation.swift.gyb

@@ -68,29 +68,35 @@ extension String : _ExpressibleByStringInterpolation {
     self = String(describing: expr)
   }
 
-% for Type in StreamableTypes:
   /// Creates a string containing the given value's textual representation.
   ///
   /// Do not call this initializer directly. It is used by the compiler when
   /// interpreting string interpolations.
   ///
   /// - SeeAlso: `ExpressibleByStringInterpolation`
-  public init(stringInterpolationSegment expr: ${Type}) {
+  public init<T: TextOutputStreamable> (stringInterpolationSegment expr: T) {
     self = _toStringReadOnlyStreamable(expr)
   }
-% end
 
-% for Type in PrintableTypes:
   /// Creates a string containing the given value's textual representation.
   ///
   /// Do not call this initializer directly. It is used by the compiler when
   /// interpreting string interpolations.
   ///
   /// - SeeAlso: `ExpressibleByStringInterpolation`
-  public init(stringInterpolationSegment expr: ${Type}) {
+  public init<T: CustomStringConvertible> (stringInterpolationSegment expr: T) {
     self = _toStringReadOnlyPrintable(expr)
   }
-% end
+
+  /// Creates a string containing the given value's textual representation.
+  ///
+  /// Do not call this initializer directly. It is used by the compiler when
+  /// interpreting string interpolations.
+  ///
+  /// - SeeAlso: `ExpressibleByStringInterpolation`
+  public init<T: TextOutputStreamable & CustomStringConvertible> (stringInterpolationSegment expr: T) {
+    self = _toStringReadOnlyStreamable(expr)
+  }
 }
 
 // ${'Local Variables'}:

test/Constraints/interpolation_segments.swift

@@ -0,0 +1,45 @@
+// RUN: %target-typecheck-verify-swift -typecheck -debug-constraints %s > %t.dump 2>&1 
+// RUN: %FileCheck %s < %t.dump
+
+// Make sure that the interpolation segments get placed into separate connected
+// components.
+// CHECK: ---Connected components---
+// CHECK-NEXT:  0: 
+// CHECK-NEXT:  1: 
+// CHECK-NEXT:  2: 
+// CHECK-NEXT:  3: 
+// CHECK-NEXT:  4: 
+// CHECK-NEXT:  5: 
+// CHECK-NEXT:  6: 
+// CHECK-NEXT:  7: 
+// CHECK-NEXT:  8: 
+// CHECK-NEXT:  9:
+
+// CHECK: (solving component #
+// CHECK: literal=3 bindings=(subtypes of) (default from ExpressibleByStringLiteral) String)
+
+// CHECK: (solving component #
+// CHECK: literal=3 bindings=(subtypes of) (default from ExpressibleByIntegerLiteral) Int)
+
+// CHECK: (solving component #
+// CHECK: literal=3 bindings=(subtypes of) (default from ExpressibleByStringLiteral) String)
+
+// CHECK: (solving component #
+// CHECK: literal=3 bindings=(subtypes of) (default from ExpressibleByIntegerLiteral) Int)
+
+// CHECK: (solving component #
+// CHECK: literal=3 bindings=(subtypes of) (default from ExpressibleByStringLiteral) String)
+
+// CHECK: (solving component #
+// CHECK: literal=3 bindings=(subtypes of) (default from ExpressibleByIntegerLiteral) Int)
+
+// CHECK: (solving component #
+// CHECK: literal=3 bindings=(subtypes of) (default from ExpressibleByStringLiteral) String)
+
+// CHECK: (solving component #
+// CHECK: literal=3 bindings=(subtypes of) (default from ExpressibleByIntegerLiteral) Int)
+
+// CHECK: (solving component #
+// CHECK: literal=3 bindings=(subtypes of) (default from ExpressibleByStringLiteral) String)
+
+_ = "\(1), \(2), \(3), \(4)"

test/api-digester/source-stability.swift.expected

@@ -12,6 +12,7 @@ Protocol IndexableBase has been removed (deprecated)
 Protocol MutableIndexable has been removed (deprecated)
 Protocol RandomAccessIndexable has been removed (deprecated)
 Protocol RangeReplaceableIndexable has been removed (deprecated)
+Constructor String.init(stringInterpolationSegment:) has been removed
 Func Array.append(contentsOf:) has been removed
 Func ArraySlice.append(contentsOf:) has been removed
 Func ContiguousArray.append(contentsOf:) has been removed
@@ -34,6 +35,7 @@ Constructor RangeReplaceableBidirectionalSlice.init(base:bounds:) has 2nd parame
 Constructor RangeReplaceableRandomAccessSlice.init(base:bounds:) has 2nd parameter type change from Range<Base.Index> to Range<RangeReplaceableRandomAccessSlice.Index>
 Constructor RangeReplaceableSlice.init(base:bounds:) has 2nd parameter type change from Range<Base.Index> to Range<RangeReplaceableSlice.Index>
 Constructor Slice.init(base:bounds:) has 2nd parameter type change from Range<Base.Index> to Range<Slice.Index>
+Constructor String.init(stringInterpolationSegment:) has 1st parameter type change from String to T
 Func AnyBidirectionalCollection.makeIterator() has return type change from AnyIterator<Element> to AnyBidirectionalCollection.Iterator
 Func AnyCollection.makeIterator() has return type change from AnyIterator<Element> to AnyCollection.Iterator
 Func AnyRandomAccessCollection.makeIterator() has return type change from AnyIterator<Element> to AnyRandomAccessCollection.Iterator

validation-test/Sema/interpolation_placeholders.swift

@@ -0,0 +1,4 @@
+// RUN: not %target-swift-frontend -typecheck %s
+
+let query = "<#...#>=\(<#...#>)&<#...#>=\(<#...#>)&<#...#>=\(<#...#>)&<#...#>=\(<#...#>)&<#...#>=\(<#...#>)&<#...#>=\(<#...#>)&<#...#>=\(<#...#>)&<#...#>=\(<#...#>)&<#...#>=\(<#...#>)&<#...#>=\(<#...#>)&<#...#>=\(<#...#>)&<#...#>=\(<#...#>)&<#...#>=\(<#...#>)&<#...#>=\(<#...#>)&<#...#>=\(<#...#>)&<#...#>=\(<#...#>)"
+