[5.1] TypeChecker: Fix dynamic replacement of protocol default implementation

lib/Sema/TypeCheckAttr.cpp

@@ -2166,6 +2166,9 @@ static FuncDecl *findReplacedAccessor(DeclName replacedVarName,
     Type replacementStorageType = getDynamicComparisonType(replacementStorage);
     results.erase(std::remove_if(results.begin(), results.end(),
         [&](ValueDecl *result) {
+          // Protocol requirements are not replaceable.
+          if (isa<ProtocolDecl>(result->getDeclContext()))
+            return true;
           // Check for static/instance mismatch.
           if (result->isStatic() != replacementStorage->isStatic())
             return true;
@@ -2247,9 +2250,13 @@ findReplacedFunction(DeclName replacedFunctionName,
   lookupReplacedDecl(replacedFunctionName, attr, replacement, results);
 
   for (auto *result : results) {
+    // Protocol requirements are not replaceable.
+    if (isa<ProtocolDecl>(result->getDeclContext()))
+      continue;
     // Check for static/instance mismatch.
     if (result->isStatic() != replacement->isStatic())
       continue;
+
     if (TC)
       TC->validateDecl(result);
     TypeMatchOptions matchMode = TypeMatchFlags::AllowABICompatible;

test/attr/Inputs/dynamicReplacementC.swift

@@ -13,3 +13,23 @@ public class K {
   public convenience init(c : Int) { self.init(i : c) }
   public final func finalFunction() {}
 }
+
+
+public protocol P {
+  var v: Int { get }
+  subscript(i: Int) -> Int { get }
+  func f()
+}
+
+extension P {
+  public var v: Int { return 0 }
+
+  public subscript(i: Int) -> Int {
+    get {
+      return 0
+    }
+  }
+
+  public func f() {
+  }
+}

test/attr/dynamicReplacement.swift

@@ -57,3 +57,21 @@ extension undeclared { // expected-error{{use of undeclared type 'undeclared'}}
   @_dynamicReplacement(for: func) // expected-error{{replaced function 'func' could not be found}}
   func func2() -> Int { return 2 }
 }
+
+extension P {
+  @_dynamicReplacement(for: v)
+  var replacement_v : Int {
+    return 1
+  }
+
+  @_dynamicReplacement(for: subscript(_:))
+  subscript(y y: Int) -> Int {
+    get {
+      return 1
+    }
+  }
+
+  @_dynamicReplacement(for: f())
+  func replacement_f() {
+  }
+}