Check 'unsafe' within keypaths

Author: DougGregor

lib/Sema/TypeCheckEffects.cpp

@@ -613,6 +613,31 @@ class EffectsHandlingWalker : public ASTWalker {
       if (!TE->isImplicit()) {
         recurse = asImpl().checkType(TE, TE->getTypeRepr(), TE->getInstanceType());
       }
+    } else if (auto KPE = dyn_cast<KeyPathExpr>(E)) {
+      for (auto &component : KPE->getComponents()) {
+        switch (component.getKind()) {
+        case KeyPathExpr::Component::Kind::Property:
+        case KeyPathExpr::Component::Kind::Subscript: {
+          (void)asImpl().checkDeclRef(KPE, component.getDeclRef(),
+                                      component.getLoc(),
+                                      /*isImplicitlyAsync=*/false,
+                                      /*isImplicitlyThrows=*/false);
+          break;
+        }
+
+        case KeyPathExpr::Component::Kind::TupleElement:
+        case KeyPathExpr::Component::Kind::Invalid:
+        case KeyPathExpr::Component::Kind::UnresolvedProperty:
+        case KeyPathExpr::Component::Kind::UnresolvedSubscript:
+        case KeyPathExpr::Component::Kind::OptionalChain:
+        case KeyPathExpr::Component::Kind::OptionalWrap:
+        case KeyPathExpr::Component::Kind::OptionalForce:
+        case KeyPathExpr::Component::Kind::Identity:
+        case KeyPathExpr::Component::Kind::DictionaryKey:
+        case KeyPathExpr::Component::Kind::CodeCompletion:
+          break;
+        }
+      }
     }
     // Error handling validation (via checkTopLevelEffects) happens after
     // type checking. If an unchecked expression is still around, the code was

test/Unsafe/safe.swift

@@ -124,6 +124,13 @@ func metatypes() {
   let _: Any.Type = unsafe UnsafeType.self
 }
 
+func testKeyPath() {
+  // expected-warning@+1{{expression uses unsafe constructs but is not marked with 'unsafe'}}
+  _ = \HasProperties.computedUnsafe // expected-note{{reference to unsafe property 'computedUnsafe'}}
+
+  _ = unsafe \HasProperties.computedUnsafe
+}
+
 // Parsing of `unsafe` expressions.
 func testUnsafePositionError() -> Int {
   return 3 + unsafe unsafeInt() // expected-error{{'unsafe' cannot appear to the right of a non-assignment operator}}