Add additional lifetime dependence diagnostics

Author: meg-gupta

include/swift/AST/DiagnosticsSema.def

@@ -7786,6 +7786,11 @@ ERROR(pack_iteration_where_clause_not_supported, none,
        "lifetime dependence specifiers may only be used on result of "
        "functions, methods, initializers",
        ())
-
+ ERROR(lifetime_dependence_invalid_return_type, none,
+       "lifetime dependence specifiers can only be specifier on ~Escapable "
+       "results", ())
+ ERROR(lifetime_dependence_missing_ownership_modifier, none,
+       "lifetime dependence can only be specified on parameters with ownership "
+       "modifiers (borrowing, consuming, inout)", ())
 #define UNDEFINE_DIAGNOSTIC_MACROS
 #include "DefineDiagnosticMacros.h"

lib/Sema/TypeCheckDecl.cpp

@@ -2577,8 +2577,8 @@ static Type validateParameterType(ParamDecl *decl) {
 }
 
 llvm::Optional<LifetimeDependenceInfo> validateLifetimeDependenceInfo(
-    LifetimeDependentReturnTypeRepr *lifetimeDependentRepr, Decl *decl,
-    bool allowIndex) {
+    LifetimeDependentReturnTypeRepr *lifetimeDependentRepr, Type resultTy,
+    Decl *decl, bool allowIndex) {
   auto *afd = cast<AbstractFunctionDecl>(decl);
   auto *dc = decl->getDeclContext();
   auto &ctx = dc->getASTContext();
@@ -2592,26 +2592,35 @@ llvm::Optional<LifetimeDependenceInfo> validateLifetimeDependenceInfo(
     auto loc = specifier.getLoc();
     auto kind = specifier.getLifetimeDependenceKind();
 
-    // Sema cannot diagnose illegal lifetime dependence kinds when no
-    // ownership parameter modifiers are specified. They can be diagnosed
-    // later in SIL.
-    if (ownership != ValueOwnership::Default) {
-      if (kind == LifetimeDependenceKind::Borrow &&
-          ownership != ValueOwnership::Shared) {
-        diags.diagnose(loc, diag::lifetime_dependence_cannot_use_kind, "borrow",
-                       getOwnershipSpelling(ownership));
-        return true;
-      } else if (kind == LifetimeDependenceKind::Mutate &&
-                 ownership != ValueOwnership::InOut) {
-        diags.diagnose(loc, diag::lifetime_dependence_cannot_use_kind, "mutate",
-                       getOwnershipSpelling(ownership));
-        return true;
-      } else if (kind == LifetimeDependenceKind::Consume &&
-                 ownership != ValueOwnership::Owned) {
-        diags.diagnose(loc, diag::lifetime_dependence_cannot_use_kind,
-                       "consume", getOwnershipSpelling(ownership));
-        return true;
-      }
+    /* TODO: Enable this
+    if (TypeChecker::conformsToKnownProtocol(resultTy,
+                                             InvertibleProtocolKind::Escapable,
+                                             dc->getParentModule())) {
+      diags.diagnose(loc, diag::lifetime_dependence_invalid_return_type);
+      return true;
+    }
+    */
+    if (ownership == ValueOwnership::Default) {
+      diags.diagnose(loc, diag::lifetime_dependence_missing_ownership_modifier);
+      return true;
+    }
+    if (kind == LifetimeDependenceKind::Borrow &&
+        ownership != ValueOwnership::Shared) {
+      diags.diagnose(loc, diag::lifetime_dependence_cannot_use_kind, "borrow",
+                     getOwnershipSpelling(ownership));
+      return true;
+    }
+    if (kind == LifetimeDependenceKind::Mutate &&
+        ownership != ValueOwnership::InOut) {
+      diags.diagnose(loc, diag::lifetime_dependence_cannot_use_kind, "mutate",
+                     getOwnershipSpelling(ownership));
+      return true;
+    }
+    if (kind == LifetimeDependenceKind::Consume &&
+        ownership != ValueOwnership::Owned) {
+      diags.diagnose(loc, diag::lifetime_dependence_cannot_use_kind, "consume",
+                     getOwnershipSpelling(ownership));
+      return true;
     }
     if (copyLifetimeParamIndices.test(paramIndexToSet) ||
         borrowLifetimeParamIndices.test(paramIndexToSet)) {
@@ -2846,16 +2855,6 @@ InterfaceTypeRequest::evaluate(Evaluator &eval, ValueDecl *D) const {
       }
     }
 
-    auto *returnTypeRepr = AFD->getResultTypeRepr();
-    llvm::Optional<LifetimeDependenceInfo> lifetimeDependenceInfo;
-    if (returnTypeRepr) {
-      if (auto *lifetimeDependentRepr =
-              dyn_cast<LifetimeDependentReturnTypeRepr>(returnTypeRepr)) {
-        lifetimeDependenceInfo = validateLifetimeDependenceInfo(
-            lifetimeDependentRepr, D, /*allowIndex*/ false);
-      }
-    }
-
     // Result
     Type resultTy;
     if (auto fn = dyn_cast<FuncDecl>(D)) {
@@ -2867,6 +2866,16 @@ InterfaceTypeRequest::evaluate(Evaluator &eval, ValueDecl *D) const {
       resultTy = TupleType::getEmpty(AFD->getASTContext());
     }
 
+    auto *returnTypeRepr = AFD->getResultTypeRepr();
+    llvm::Optional<LifetimeDependenceInfo> lifetimeDependenceInfo;
+    if (returnTypeRepr) {
+      if (auto *lifetimeDependentRepr =
+              dyn_cast<LifetimeDependentReturnTypeRepr>(returnTypeRepr)) {
+        lifetimeDependenceInfo = validateLifetimeDependenceInfo(
+            lifetimeDependentRepr, resultTy, D, /*allowIndex*/ false);
+      }
+    }
+
     // (Args...) -> Result
     Type funcTy;
 

lib/Sema/TypeCheckType.cpp

@@ -4608,7 +4608,6 @@ TypeResolver::resolveResultDependsOnTypeRepr(ResultDependsOnTypeRepr *repr,
 
 NeverNullType TypeResolver::resolveLifetimeDependentReturnTypeRepr(
     LifetimeDependentReturnTypeRepr *repr, TypeResolutionOptions options) {
-
   if (!options.is(TypeResolverContext::FunctionResult)) {
     diagnoseInvalid(
         repr, repr->getSpecifierLoc(),

test/Sema/explicit_lifetime_dependence_specifiers.swift

@@ -16,6 +16,16 @@ struct MutableBufferView : ~Escapable, ~Copyable {
   }
 }
 
+class Klass {}
+
+struct WrapperStruct {
+  let k: Klass
+}
+
+func invalidLifetimeDependenceOnEscapable(_ w: borrowing WrapperStruct) -> Klass {
+  return w.k
+}
+
 func incorrectSelfInvalidLifetimeDependence(_ x: borrowing BufferView) -> _borrow(self) BufferView { // expected-error{{invalid lifetime dependence specifier, self is valid in non-static methods only}}
   return BufferView(x.ptr)
 }
@@ -52,13 +62,11 @@ func borrowingParamInvalidLifetimeDependence2(_ x: borrowing BufferView) -> _mut
   return BufferView(x.ptr)
 }
 
-// Sema cannot diagnose this
-func implicitBorrowingParamInvalidLifetimeDependence1(_ x: BufferView) -> _consume(x) BufferView {
+func implicitBorrowingParamInvalidLifetimeDependence1(_ x: BufferView) -> _consume(x) BufferView { // expected-error{{lifetime dependence can only be specified on parameters with ownership modifiers (borrowing, consuming, inout)}}
   return BufferView(x.ptr)
 }
 
-// Sema cannot diagnose this
-func implicitBorrowingParamInvalidLifetimeDependence2(_ x: BufferView) -> _mutate(x) BufferView {
+func implicitBorrowingParamInvalidLifetimeDependence2(_ x: BufferView) -> _mutate(x) BufferView {// expected-error{{lifetime dependence can only be specified on parameters with ownership modifiers (borrowing, consuming, inout)}}
   return BufferView(x.ptr)
 }