[ConstraintSystem] Generalize solution target to support un-initialized variables

Rename `uninitializedWrappedVar` kind to `uninitializedVar` and
allow storage of patterns and indices into pattern binding entry.

Author: xedin

include/swift/Sema/ConstraintSystem.h

@@ -1559,7 +1559,7 @@ class SolutionApplicationTarget {
     stmtCondition,
     caseLabelItem,
     patternBinding,
-    uninitializedWrappedVar,
+    uninitializedVar,
   } kind;
 
 private:
@@ -1631,9 +1631,15 @@ class SolutionApplicationTarget {
       DeclContext *dc;
     } caseLabelItem;
 
-    PatternBindingDecl *patternBinding;
+    struct {
+      /// Index into pattern binding declaration (if any).
+      unsigned index;
+      PointerUnion<VarDecl *, Pattern *> declaration;
+      /// Type associated with the declaration.
+      Type type;
+    } uninitializedVar;
 
-    VarDecl *uninitializedWrappedVar;
+    PatternBindingDecl *patternBinding;
   };
 
   // If the pattern contains a single variable that has an attached
@@ -1679,9 +1685,18 @@ class SolutionApplicationTarget {
     this->patternBinding = patternBinding;
   }
 
-  SolutionApplicationTarget(VarDecl *wrappedVar) {
-    kind = Kind::uninitializedWrappedVar;
-    this->uninitializedWrappedVar= wrappedVar;
+  SolutionApplicationTarget(VarDecl *uninitializedWrappedVar)
+      : kind(Kind::uninitializedVar) {
+    if (auto *PDB = uninitializedWrappedVar->getParentPatternBinding()) {
+      patternBinding = PDB;
+      uninitializedVar.index =
+          PDB->getPatternEntryIndexForVarDecl(uninitializedWrappedVar);
+    } else {
+      uninitializedVar.index = 0;
+    }
+
+    uninitializedVar.declaration = uninitializedWrappedVar;
+    uninitializedVar.type = Type();
   }
 
   /// Form a target for the initialization of a pattern from an expression.
@@ -1703,8 +1718,10 @@ class SolutionApplicationTarget {
 
   /// Form a target for a property with an attached property wrapper that is
   /// initialized out-of-line.
-  static SolutionApplicationTarget forUninitializedWrappedVar(
-      VarDecl *wrappedVar);
+  static SolutionApplicationTarget
+  forUninitializedWrappedVar(VarDecl *wrappedVar) {
+    return {wrappedVar};
+  }
 
   /// Form a target for a synthesized property wrapper initializer.
   static SolutionApplicationTarget forPropertyWrapperInitializer(
@@ -1719,7 +1736,7 @@ class SolutionApplicationTarget {
     case Kind::stmtCondition:
     case Kind::caseLabelItem:
     case Kind::patternBinding:
-    case Kind::uninitializedWrappedVar:
+    case Kind::uninitializedVar:
       return nullptr;
     }
     llvm_unreachable("invalid expression type");
@@ -1742,8 +1759,13 @@ class SolutionApplicationTarget {
     case Kind::patternBinding:
       return patternBinding->getDeclContext();
 
-    case Kind::uninitializedWrappedVar:
-      return uninitializedWrappedVar->getDeclContext();
+    case Kind::uninitializedVar: {
+      if (auto *wrappedVar =
+              uninitializedVar.declaration.dyn_cast<VarDecl *>())
+        return wrappedVar->getDeclContext();
+
+      return patternBinding->getInitContext(uninitializedVar.index);
+    }
     }
     llvm_unreachable("invalid decl context type");
   }
@@ -1915,7 +1937,7 @@ class SolutionApplicationTarget {
     case Kind::stmtCondition:
     case Kind::caseLabelItem:
     case Kind::patternBinding:
-    case Kind::uninitializedWrappedVar:
+    case Kind::uninitializedVar:
       return None;
 
     case Kind::function:
@@ -1930,7 +1952,7 @@ class SolutionApplicationTarget {
     case Kind::function:
     case Kind::caseLabelItem:
     case Kind::patternBinding:
-    case Kind::uninitializedWrappedVar:
+    case Kind::uninitializedVar:
       return None;
 
     case Kind::stmtCondition:
@@ -1945,7 +1967,7 @@ class SolutionApplicationTarget {
     case Kind::function:
     case Kind::stmtCondition:
     case Kind::patternBinding:
-    case Kind::uninitializedWrappedVar:
+    case Kind::uninitializedVar:
       return None;
 
     case Kind::caseLabelItem:
@@ -1960,7 +1982,7 @@ class SolutionApplicationTarget {
     case Kind::function:
     case Kind::stmtCondition:
     case Kind::caseLabelItem:
-    case Kind::uninitializedWrappedVar:
+    case Kind::uninitializedVar:
       return nullptr;
 
     case Kind::patternBinding:
@@ -1978,8 +2000,8 @@ class SolutionApplicationTarget {
     case Kind::patternBinding:
       return nullptr;
 
-    case Kind::uninitializedWrappedVar:
-      return uninitializedWrappedVar;
+    case Kind::uninitializedVar:
+      return uninitializedVar.declaration.dyn_cast<VarDecl *>();
     }
     llvm_unreachable("invalid case label type");
   }
@@ -2013,8 +2035,13 @@ class SolutionApplicationTarget {
     case Kind::patternBinding:
       return patternBinding->getSourceRange();
 
-    case Kind::uninitializedWrappedVar:
-      return uninitializedWrappedVar->getSourceRange();
+    case Kind::uninitializedVar: {
+      if (auto *wrappedVar =
+              uninitializedVar.declaration.dyn_cast<VarDecl *>()) {
+        return wrappedVar->getSourceRange();
+      }
+      return uninitializedVar.declaration.get<Pattern *>()->getSourceRange();
+    }
     }
     llvm_unreachable("invalid target type");
   }
@@ -2037,8 +2064,13 @@ class SolutionApplicationTarget {
     case Kind::patternBinding:
       return patternBinding->getLoc();
 
-    case Kind::uninitializedWrappedVar:
-      return uninitializedWrappedVar->getLoc();
+    case Kind::uninitializedVar: {
+      if (auto *wrappedVar =
+          uninitializedVar.declaration.dyn_cast<VarDecl *>()) {
+        return wrappedVar->getLoc();
+      }
+      return uninitializedVar.declaration.get<Pattern *>()->getLoc();
+    }
     }
     llvm_unreachable("invalid target type");
   }

lib/Sema/CSApply.cpp

@@ -9086,7 +9086,7 @@ SolutionApplicationTarget SolutionApplicationTarget::walk(ASTWalker &walker) {
   case Kind::patternBinding:
     return *this;
 
-  case Kind::uninitializedWrappedVar:
+  case Kind::uninitializedVar:
     return *this;
   }
 

lib/Sema/CSGen.cpp

@@ -3955,14 +3955,17 @@ bool ConstraintSystem::generateConstraints(
     return hadError;
   }
 
-  case SolutionApplicationTarget::Kind::uninitializedWrappedVar: {
-    auto *wrappedVar = target.getAsUninitializedWrappedVar();
-    auto propertyType = getVarType(wrappedVar);
-    if (propertyType->hasError())
-      return true;
+  case SolutionApplicationTarget::Kind::uninitializedVar: {
+    if (auto *wrappedVar = target.getAsUninitializedWrappedVar()) {
+      auto propertyType = getVarType(wrappedVar);
+      if (propertyType->hasError())
+        return true;
 
-    return generateWrappedPropertyTypeConstraints(
+      return generateWrappedPropertyTypeConstraints(
         *this, /*initializerType=*/Type(), wrappedVar, propertyType);
+    }
+
+    llvm_unreachable("Unsupported un-initialized variable");
   }
   }
 }

lib/Sema/ConstraintSystem.cpp

@@ -5419,11 +5419,6 @@ SolutionApplicationTarget SolutionApplicationTarget::forForEachStmt(
   return target;
 }
 
-SolutionApplicationTarget
-SolutionApplicationTarget::forUninitializedWrappedVar(VarDecl *wrappedVar) {
-  return SolutionApplicationTarget(wrappedVar);
-}
-
 SolutionApplicationTarget
 SolutionApplicationTarget::forPropertyWrapperInitializer(
     VarDecl *wrappedVar, DeclContext *dc, Expr *initializer) {

lib/Sema/TypeCheckConstraints.cpp

@@ -295,7 +295,7 @@ void constraints::performSyntacticDiagnosticsForTarget(
   case SolutionApplicationTarget::Kind::stmtCondition:
   case SolutionApplicationTarget::Kind::caseLabelItem:
   case SolutionApplicationTarget::Kind::patternBinding:
-  case SolutionApplicationTarget::Kind::uninitializedWrappedVar:
+  case SolutionApplicationTarget::Kind::uninitializedVar:
     // Nothing to do for these.
     return;
   }