[ConstraintSystem] Solution application target for uninitialized pattern binding

Author: xedin

include/swift/Sema/ConstraintSystem.h

@@ -1699,6 +1699,17 @@ class SolutionApplicationTarget {
     uninitializedVar.type = Type();
   }
 
+  SolutionApplicationTarget(PatternBindingDecl *binding, unsigned index,
+                            Pattern *var, Type patternTy)
+      : kind(Kind::uninitializedVar) {
+    assert(patternBinding);
+
+    patternBinding = binding;
+    uninitializedVar.index = index;
+    uninitializedVar.declaration = var;
+    uninitializedVar.type = patternTy;
+  }
+
   /// Form a target for the initialization of a pattern from an expression.
   static SolutionApplicationTarget forInitialization(
       Expr *initializer, DeclContext *dc, Type patternType, Pattern *pattern,
@@ -1723,6 +1734,12 @@ class SolutionApplicationTarget {
     return {wrappedVar};
   }
 
+  static SolutionApplicationTarget
+  forUninitializedVar(PatternBindingDecl *binding, unsigned index, Pattern *var,
+                      Type patternTy) {
+    return {binding, index, var, patternTy};
+  }
+
   /// Form a target for a synthesized property wrapper initializer.
   static SolutionApplicationTarget forPropertyWrapperInitializer(
       VarDecl *wrappedVar, DeclContext *dc, Expr *initializer);
@@ -1821,6 +1838,9 @@ class SolutionApplicationTarget {
 
   /// For a pattern initialization target, retrieve the pattern.
   Pattern *getInitializationPattern() const {
+    if (kind == Kind::uninitializedVar)
+      return uninitializedVar.declaration.get<Pattern *>();
+
     assert(kind == Kind::expression);
     assert(expression.contextualPurpose == CTP_Initialization);
     return expression.pattern;
@@ -1925,6 +1945,12 @@ class SolutionApplicationTarget {
   }
 
   void setPattern(Pattern *pattern) {
+    if (kind == Kind::uninitializedVar) {
+      assert(uninitializedVar.declaration.is<Pattern *>());
+      uninitializedVar.declaration = pattern;
+      return;
+    }
+
     assert(kind == Kind::expression);
     assert(expression.contextualPurpose == CTP_Initialization ||
            expression.contextualPurpose == CTP_ForEachStmt);
@@ -2006,6 +2032,66 @@ class SolutionApplicationTarget {
     llvm_unreachable("invalid case label type");
   }
 
+  Pattern *getAsUninitializedVar() const {
+    switch (kind) {
+    case Kind::expression:
+    case Kind::function:
+    case Kind::stmtCondition:
+    case Kind::caseLabelItem:
+    case Kind::patternBinding:
+      return nullptr;
+
+    case Kind::uninitializedVar:
+      return uninitializedVar.declaration.dyn_cast<Pattern *>();
+    }
+    llvm_unreachable("invalid case label type");
+  }
+
+  Type getTypeOfUninitializedVar() const {
+    switch (kind) {
+    case Kind::expression:
+    case Kind::function:
+    case Kind::stmtCondition:
+    case Kind::caseLabelItem:
+    case Kind::patternBinding:
+      return nullptr;
+
+    case Kind::uninitializedVar:
+      return uninitializedVar.type;
+    }
+    llvm_unreachable("invalid case label type");
+  }
+
+  PatternBindingDecl *getPatternBindingOfUninitializedVar() const {
+    switch (kind) {
+    case Kind::expression:
+    case Kind::function:
+    case Kind::stmtCondition:
+    case Kind::caseLabelItem:
+    case Kind::patternBinding:
+      return nullptr;
+
+    case Kind::uninitializedVar:
+      return patternBinding;
+    }
+    llvm_unreachable("invalid case label type");
+  }
+
+  unsigned getIndexOfUninitializedVar() const {
+    switch (kind) {
+    case Kind::expression:
+    case Kind::function:
+    case Kind::stmtCondition:
+    case Kind::caseLabelItem:
+    case Kind::patternBinding:
+      return 0;
+
+    case Kind::uninitializedVar:
+      return uninitializedVar.index;
+    }
+    llvm_unreachable("invalid case label type");
+  }
+
   BraceStmt *getFunctionBody() const {
     assert(kind == Kind::function);
     return function.body;