[Parse] InitAccessors: Parse initializer exprs associated with computed properties that have init accessor

Initialization expressions are not allowed on computed properties
but if a property has `init` accessor it should be allowed because
it could be used by a memberwise initializer.

Author: xedin

lib/Parse/ParseExpr.cpp

@@ -1059,14 +1059,14 @@ bool Parser::isStartOfGetSetAccessor() {
   // The only case this can happen is if the accessor label is immediately after
   // a brace (possibly preceded by attributes).  "get" is implicit, so it can't
   // be checked for.  Conveniently however, get/set properties are not allowed
-  // to have initializers, so we don't have an ambiguity, we just have to check
-  // for observing accessors.
+  // to have initializers unless they have `init` accessor, so we don't have an
+  // ambiguity, we just have to check for observing accessors and init accessor.
   //
   // If we have a 'didSet' or a 'willSet' label, disambiguate immediately as
   // an accessor block.
   Token NextToken = peekToken();
   if (NextToken.isContextualKeyword("didSet") ||
-      NextToken.isContextualKeyword("willSet"))
+      NextToken.isContextualKeyword("willSet") || NextToken.is(tok::kw_init))
     return true;
 
   // If we don't have attributes, then it cannot be an accessor block.
@@ -1087,9 +1087,9 @@ bool Parser::isStartOfGetSetAccessor() {
       skipSingle();
   }
 
-  // Check if we have 'didSet'/'willSet' after attributes.
+  // Check if we have 'didSet'/'willSet' or 'init' after attributes.
   return Tok.isContextualKeyword("didSet") ||
-         Tok.isContextualKeyword("willSet");
+         Tok.isContextualKeyword("willSet") || Tok.is(tok::kw_init);
 }
 
 /// Recover invalid uses of trailing closures in a situation

test/decl/var/init_accessors.swift

@@ -444,3 +444,24 @@ func test_memberwise_ordering() {
 
   _ = Test5(_a: 0, _b: 1, c: 2) // Ok
 }
+
+func test_default_arguments_are_analyzed() {
+  struct Test {
+    var pair: (Int, Int) = (0, 1) { // Ok
+      init {}
+    }
+
+    var other: (Int, String) = ("", 42) {
+      // expected-error@-1 {{cannot convert value of type '(String, Int)' to specified type '(Int, String)'}}
+      init(initialValue) {}
+    }
+
+    var otherPair = (0, 1) {
+      // expected-error@-1 {{computed property must have an explicit type}}
+      init(initalValue) {}
+
+      get { 42 }
+      // expected-error@-1 {{cannot convert return expression of type 'Int' to return type '(Int, Int)'}}
+    }
+  }
+}