[CSDiagnostics] InitAccessors: Implement invalid member reference diagnostics within init accessors

Author: xedin

include/swift/AST/DiagnosticsSema.def

@@ -7346,7 +7346,11 @@ ERROR(invalid_use_of_self_in_init_accessor,none,
       "'self' within init accessors can only be used to reference "
       "properties listed in 'initializes' and 'accesses'; "
       "init accessors are run before 'self' is fully available", ())
-
+ERROR(init_accessor_invalid_member_ref,none,
+      "cannot reference instance member %0; init accessors can only "
+      "refer to instance properties listed in 'initializes' and "
+      "'accesses' attributes",
+      (DeclNameRef))
 
 #define UNDEFINE_DIAGNOSTIC_MACROS
 #include "DefineDiagnosticMacros.h"

lib/Sema/CSDiagnostics.cpp

@@ -9058,3 +9058,8 @@ bool MissingEachForValuePackReference::diagnoseAsError() {
 
   return true;
 }
+
+bool InvalidMemberReferenceWithinInitAccessor::diagnoseAsError() {
+  emitDiagnostic(diag::init_accessor_invalid_member_ref, MemberName);
+  return true;
+}

lib/Sema/CSDiagnostics.h

@@ -3015,6 +3015,19 @@ class MissingEachForValuePackReference final : public FailureDiagnostic {
   bool diagnoseAsError() override;
 };
 
+class InvalidMemberReferenceWithinInitAccessor final
+    : public FailureDiagnostic {
+  DeclNameRef MemberName;
+
+public:
+  InvalidMemberReferenceWithinInitAccessor(const Solution &solution,
+                                           DeclNameRef memberName,
+                                           ConstraintLocator *locator)
+      : FailureDiagnostic(solution, locator), MemberName(memberName) {}
+
+  bool diagnoseAsError() override;
+};
+
 } // end namespace constraints
 } // end namespace swift
 

lib/Sema/CSFix.cpp

@@ -2799,7 +2799,9 @@ IgnoreMissingEachKeyword::create(ConstraintSystem &cs, Type valuePackTy,
 
 bool AllowInvalidMemberReferenceInInitAccessor::diagnose(
     const Solution &solution, bool asNote) const {
-  return false;
+  InvalidMemberReferenceWithinInitAccessor failure(solution, MemberName,
+                                                   getLocator());
+  return failure.diagnose(asNote);
 }
 
 AllowInvalidMemberReferenceInInitAccessor *

test/decl/var/init_accessors.swift

@@ -173,3 +173,51 @@ func test_invalid_self_uses() {
     static func test<T>(_: T) {}
   }
 }
+
+func test_invalid_references() {
+  struct Test {
+    var _a: Int
+    var _b: Int
+
+    var c: String
+    static var c: String = ""
+
+    var _d: String
+
+    var data: Int {
+      init(initialValue) initializes(_a) accesses(_d) {
+        _a = initialValue // Ok
+
+        print(_d) // Ok
+        self._d = "" // Ok
+
+        if self._b > 0 { // expected-error {{cannot reference instance member '_b'; init accessors can only refer to instance properties listed in 'initializes' and 'accesses' attributes}}
+        }
+
+        let x = c.lowercased()
+        // expected-error@-1 {{static member 'c' cannot be used on instance of type 'Test'}}
+
+        print(Test.c.lowercased()) // Ok
+
+        guard let v = test() else {
+          // expected-error@-1 {{cannot reference instance member 'test'; init accessors can only refer to instance properties listed in 'initializes' and 'accesses' attributes}}
+          return
+        }
+
+        _ = {
+          if true {
+            print(_b)
+            // expected-error@-1 {{cannot reference instance member '_b'; init accessors can only refer to instance properties listed in 'initializes' and 'accesses' attributes}}
+            print(self._b)
+            // expected-error@-1 {{cannot reference instance member '_b'; init accessors can only refer to instance properties listed in 'initializes' and 'accesses' attributes}}
+          }
+        }
+      }
+
+      get { _a }
+      set { }
+    }
+
+    func test() -> Int? { 42 }
+  }
+}