Merge pull request #4459 from DougGregor/fix-crashes-rdar27940842

[Type checker] Improve recovery from erroneous operators in types.

Author: DougGregor

lib/Sema/TypeCheckDecl.cpp

@@ -4335,6 +4335,8 @@ class DeclChecker : public DeclVisitor<DeclChecker> {
                         dc->getDeclaredInterfaceType())
               .fixItInsert(FD->getAttributeInsertionLoc(/*forModifier=*/true),
                            "static ");
+
+            FD->setStatic();
           } else {
             TC.diagnose(FD->getLoc(), diag::nonfinal_operator_in_class,
                         operatorName, dc->getDeclaredInterfaceType())
@@ -4350,6 +4352,7 @@ class DeclChecker : public DeclVisitor<DeclChecker> {
                     dc->getDeclaredInterfaceType())
           .fixItInsert(FD->getAttributeInsertionLoc(/*forModifier=*/true),
                        "static ");
+        FD->setStatic();
       }
     } else if (!dc->isModuleScopeContext()) {
       TC.diagnose(FD, diag::operator_in_local_scope);

lib/Sema/TypeCheckError.cpp

@@ -406,6 +406,12 @@ class ApplyClassifier {
     SmallVector<Expr*, 4> args;
     auto fnRef = AbstractFunction::decomposeApply(E, args);
 
+    // If any of the arguments didn't type check, fail.
+    for (auto arg : args) {
+      if (!arg->getType() || arg->getType()->is<ErrorType>())
+        return Classification::forInvalidCode();
+    }
+
     // If we're applying more arguments than the natural argument
     // count, then this is a call to the opaque value returned from
     // the function.

test/decl/func/operator.swift

@@ -336,3 +336,20 @@ extension P3 {
   // Okay: refers to P3
   static func %%%%(lhs: P3, rhs: Unrelated) -> Unrelated { }
 }
+
+// rdar://problem/27940842 - recovery with a non-static '=='.
+class C5 {
+  func == (lhs: C5, rhs: C5) -> Bool { return false } // expected-error{{operator '==' declared in type 'C5' must be 'static'}}
+
+  func test1(x: C5) {
+    _ = x == x
+  }
+}
+
+class C6 {
+  static func == (lhs: C6, rhs: C6) -> Bool { return false }
+
+  func test1(x: C6) {
+    if x == x && x = x { } // expected-error{{cannot assign to value: '&&' returns immutable value}}
+  }
+}