[diag] fix incorrect diagnostic when unwrapping double optional

Author: Suyash Srijan

lib/Sema/CSDiagnostics.cpp

@@ -580,8 +580,21 @@ bool MissingOptionalUnwrapFailure::diagnoseAsError() {
     anchor = assignExpr->getSrc();
 
   auto *unwrapped = anchor->getValueProvidingExpr();
-  auto type = getType(anchor)->getRValueType();
-
+  Type type = [&] {
+    // The anchor could be pointing to an OptionalEvaluationExpr, with the sub
+    // expression being a CallExpr, UnresolvedDotExpr, etc which could produce
+    // an >= 1 optional, so let's return the type of the sub expression.
+    if (auto OEE = dyn_cast<OptionalEvaluationExpr>(anchor)) {
+      if (auto subTy = getType(OEE->getSubExpr())) {
+        if (!subTy->hasLValueType() && subTy->getOptionalObjectType()) {
+          return subTy->getRValueType();
+        }
+      }
+    }
+    // Just return the type of the anchor
+    return getType(anchor)->getRValueType();
+  }();
+  
   auto *tryExpr = dyn_cast<OptionalTryExpr>(unwrapped);
   if (!tryExpr)
     return diagnoseUnwrap(getConstraintSystem(), unwrapped, type);

test/Constraints/fixes.swift

@@ -243,3 +243,47 @@ func moreComplexUnwrapFixes() {
 
   }
 }
+
+struct FooStruct {
+  func a() -> Int?? { return 10 }
+
+  var b: Int?? {
+    return 15
+  }
+
+  func c() -> Int??? { return 20 }
+
+  var d: Int??? {
+    return 25
+  }
+
+  let e: BarStruct? = BarStruct()
+}
+
+struct BarStruct {
+  func a() -> Int? { return 30 }
+  var b: Int?? {
+    return 35
+  }
+}
+
+let thing: FooStruct? = FooStruct()
+
+let _: Int? = thing?.a() // expected-error {{value of optional type 'Int??' must be unwrapped to a value of type 'Int?'}}
+// expected-note@-1{{coalesce}}
+// expected-note@-2{{force-unwrap}}
+let _: Int? = thing?.b // expected-error {{value of optional type 'Int??' must be unwrapped to a value of type 'Int?'}}
+// expected-note@-1{{coalesce}}
+// expected-note@-2{{force-unwrap}}
+let _: Int?? = thing?.c() // expected-error {{value of optional type 'Int???' must be unwrapped to a value of type 'Int??'}}
+// expected-note@-1{{coalesce}}
+// expected-note@-2{{force-unwrap}}
+let _: Int?? = thing?.d // expected-error {{value of optional type 'Int???' must be unwrapped to a value of type 'Int??'}}
+// expected-note@-1{{coalesce}}
+// expected-note@-2{{force-unwrap}}
+let _: Int = thing?.e?.a() // expected-error {{value of optional type 'Int?' must be unwrapped to a value of type 'Int'}}
+// expected-note@-1{{coalesce}}
+// expected-note@-2{{force-unwrap}}
+let _: Int? = thing?.e?.b // expected-error {{value of optional type 'Int??' must be unwrapped to a value of type 'Int?'}}
+// expected-note@-1{{coalesce}}
+// expected-note@-2{{force-unwrap}}