[CS] Remove external type logic from getTypeForPattern

This shouldn't be necessary, we should be able to
solve with type variables instead. This makes sure
we don't end up with weird special cases that only
occur when an external type is present.

Author: hamishknight

lib/Sema/CSDiagnostics.cpp

@@ -8756,7 +8756,7 @@ bool InvalidWeakAttributeUse::diagnoseAsError() {
     return false;
 
   auto *var = pattern->getDecl();
-  auto varType = OptionalType::get(getType(var));
+  auto varType = getType(var);
 
   auto diagnostic =
       emitDiagnosticAt(var, diag::invalid_ownership_not_optional,

lib/Sema/CSGen.cpp

@@ -2438,17 +2438,12 @@ namespace {
     /// \param locator The locator to use for generated constraints and
     /// type variables.
     ///
-    /// \param externalPatternType The type imposed by the enclosing pattern,
-    /// if any. This will be non-null in cases where there is, e.g., a
-    /// pattern such as "is SubClass".
-    ///
     /// \param bindPatternVarsOneWay When true, generate fresh type variables
     /// for the types of each variable declared within the pattern, along
     /// with a one-way constraint binding that to the type to which the
     /// variable will be ascribed or inferred.
     Type getTypeForPattern(
        Pattern *pattern, ConstraintLocatorBuilder locator,
-       Type externalPatternType,
        bool bindPatternVarsOneWay,
        PatternBindingDecl *patternBinding = nullptr,
        unsigned patternBindingIndex = 0) {
@@ -2476,19 +2471,11 @@ namespace {
       case PatternKind::Paren: {
         auto *paren = cast<ParenPattern>(pattern);
 
-        // Parentheses don't affect the canonical type, but record them as
-        // type sugar.
-        if (externalPatternType &&
-            isa<ParenType>(externalPatternType.getPointer())) {
-          externalPatternType = cast<ParenType>(externalPatternType.getPointer())
-              ->getUnderlyingType();
-        }
-
         auto *subPattern = paren->getSubPattern();
         auto underlyingType = getTypeForPattern(
             subPattern,
             locator.withPathElement(LocatorPathElt::PatternMatch(subPattern)),
-            externalPatternType, bindPatternVarsOneWay);
+            bindPatternVarsOneWay);
 
         if (!underlyingType)
           return Type();
@@ -2497,7 +2484,7 @@ namespace {
       }
       case PatternKind::Binding: {
         auto *subPattern = cast<BindingPattern>(pattern)->getSubPattern();
-        auto type = getTypeForPattern(subPattern, locator, externalPatternType,
+        auto type = getTypeForPattern(subPattern, locator,
                                       bindPatternVarsOneWay);
 
         if (!type)
@@ -2526,9 +2513,7 @@ namespace {
             locator.withPathElement(LocatorPathElt::PatternMatch(pattern));
 
         // Always prefer a contextual type when it's available.
-        if (externalPatternType) {
-          type = externalPatternType;
-        } else if (auto *initializer = getInitializerExpr()) {
+        if (auto *initializer = getInitializerExpr()) {
           // For initialization always assume a type of initializer.
           type = CS.getType(initializer)->getRValueType();
         } else {
@@ -2608,18 +2593,13 @@ namespace {
           // diagnostic in the middle of the solver path.
 
           CS.addConstraint(ConstraintKind::OneWayEqual, oneWayVarType,
-                           externalPatternType ? externalPatternType : varType,
-                           locator);
+                           varType, locator);
         }
 
         // Ascribe a type to the declaration so it's always available to
         // constraint system.
         if (oneWayVarType) {
           CS.setType(var, oneWayVarType);
-        } else if (externalPatternType) {
-          // If there is an externally imposed type, that's what the
-          // declaration is going to be bound to.
-          CS.setType(var, externalPatternType);
         } else {
           // Otherwise, let's use the type of the pattern. The type
           // of the declaration has to be r-value, so let's add an
@@ -2708,7 +2688,7 @@ namespace {
         Type subPatternType = getTypeForPattern(
             subPattern,
             locator.withPathElement(LocatorPathElt::PatternMatch(subPattern)),
-            openedType, bindPatternVarsOneWay);
+            bindPatternVarsOneWay);
 
         if (!subPatternType)
           return Type();
@@ -2731,38 +2711,16 @@ namespace {
       case PatternKind::Tuple: {
         auto tuplePat = cast<TuplePattern>(pattern);
 
-        // If there's an externally-imposed type, decompose it into element
-        // types so long as we have the right number of such types.
-        SmallVector<AnyFunctionType::Param, 4> externalEltTypes;
-        if (externalPatternType) {
-          decomposeTuple(externalPatternType, externalEltTypes);
-
-          // If we have the wrong number of elements, we may not be able to
-          // provide more specific types.
-          if (tuplePat->getNumElements() != externalEltTypes.size()) {
-            externalEltTypes.clear();
-
-            // Implicit tupling.
-            if (tuplePat->getNumElements() == 1) {
-              externalEltTypes.push_back(
-                  AnyFunctionType::Param(externalPatternType));
-            }
-          }
-        }
-
         SmallVector<TupleTypeElt, 4> tupleTypeElts;
         tupleTypeElts.reserve(tuplePat->getNumElements());
         for (unsigned i = 0, e = tuplePat->getNumElements(); i != e; ++i) {
           auto &tupleElt = tuplePat->getElement(i);
-          Type externalEltType;
-          if (!externalEltTypes.empty())
-            externalEltType = externalEltTypes[i].getPlainType();
 
           auto *eltPattern = tupleElt.getPattern();
           Type eltTy = getTypeForPattern(
               eltPattern,
               locator.withPathElement(LocatorPathElt::PatternMatch(eltPattern)),
-              externalEltType, bindPatternVarsOneWay);
+              bindPatternVarsOneWay);
 
           if (!eltTy)
             return Type();
@@ -2774,25 +2732,12 @@ namespace {
       }
 
       case PatternKind::OptionalSome: {
-        // Remove an optional from the object type.
-        if (externalPatternType) {
-          Type objVar = CS.createTypeVariable(
-              CS.getConstraintLocator(
-                  locator.withPathElement(ConstraintLocator::OptionalPayload)),
-              TVO_CanBindToNoEscape);
-          CS.addConstraint(
-              ConstraintKind::OptionalObject, externalPatternType, objVar,
-              locator.withPathElement(LocatorPathElt::PatternMatch(pattern)));
-
-          externalPatternType = objVar;
-        }
-
         auto *subPattern = cast<OptionalSomePattern>(pattern)->getSubPattern();
         // The subpattern must have optional type.
         Type subPatternType = getTypeForPattern(
             subPattern,
             locator.withPathElement(LocatorPathElt::PatternMatch(subPattern)),
-            externalPatternType, bindPatternVarsOneWay);
+            bindPatternVarsOneWay);
 
         if (!subPatternType)
           return Type();
@@ -2827,7 +2772,7 @@ namespace {
           auto subPatternType = getTypeForPattern(
               subPattern,
               locator.withPathElement(LocatorPathElt::PatternMatch(subPattern)),
-              castType, bindPatternVarsOneWay);
+              bindPatternVarsOneWay);
 
           // NOTE: The order here is important! Pattern matching equality is
           // not symmetric (we need to fix that either by using a different
@@ -2912,18 +2857,6 @@ namespace {
               locator.withPathElement(LocatorPathElt::PatternMatch(pattern)));
 
           baseType = parentType;
-          // Perform member lookup into the external pattern metatype. e.g.
-          // `case let .test(tuple) as Test`.
-        } else if (externalPatternType) {
-          Type externalMetaType = MetatypeType::get(externalPatternType);
-
-          CS.addValueMemberConstraint(
-              externalMetaType, enumPattern->getName(), memberType, CurDC,
-              functionRefKind, {},
-              CS.getConstraintLocator(locator,
-                                      LocatorPathElt::PatternMatch(pattern)));
-
-          baseType = externalPatternType;
         } else {
           // Use the pattern type for member lookup.
           CS.addUnresolvedValueMemberConstraint(
@@ -2941,7 +2874,7 @@ namespace {
           Type subPatternType = getTypeForPattern(
               subPattern,
               locator.withPathElement(LocatorPathElt::PatternMatch(subPattern)),
-              Type(), bindPatternVarsOneWay);
+              bindPatternVarsOneWay);
 
           if (!subPatternType)
             return Type();
@@ -4846,7 +4779,7 @@ Type ConstraintSystem::generateConstraints(
     bool bindPatternVarsOneWay, PatternBindingDecl *patternBinding,
     unsigned patternIndex) {
   ConstraintGenerator cg(*this, nullptr);
-  return cg.getTypeForPattern(pattern, locator, Type(), bindPatternVarsOneWay,
+  return cg.getTypeForPattern(pattern, locator, bindPatternVarsOneWay,
                               patternBinding, patternIndex);
 }
 

test/Constraints/patterns.swift

@@ -564,3 +564,7 @@ struct TestIUOMatchOp {
     if case self = self {}
   }
 }
+
+struct TestRecursiveVarRef<T> {
+  lazy var e: () -> Int = {e}()
+}