[Sema] Forbid stored property marked SPI in frozen structs

Author: xymus

include/swift/AST/DiagnosticsSema.def

@@ -1709,6 +1709,9 @@ ERROR(spi_attribute_on_protocol_requirement,none,
       "protocol requirement %0 cannot be declared '@_spi' without "
       "a default implementation in a protocol extension",
       (DeclName))
+ERROR(spi_attribute_on_frozen_stored_properties,none,
+      "stored property %0 cannot be declared '@_spi' in a '@frozen' struct",
+      (DeclName))
 
 // Opaque return types
 ERROR(opaque_type_invalid_constraint,none,

lib/Sema/TypeCheckAttr.cpp

@@ -908,6 +908,14 @@ void AttributeChecker::visitSPIAccessControlAttr(SPIAccessControlAttr *attr) {
                               diag::spi_attribute_on_protocol_requirement,
                               VD->getName());
     }
+
+    // Forbid stored properties marked SPI in frozen types.
+    if (auto property = dyn_cast<AbstractStorageDecl>(VD))
+      if (auto DC = dyn_cast<NominalTypeDecl>(D->getDeclContext()))
+        if (property->hasStorage() && !DC->isFormallyResilient())
+          diagnoseAndRemoveAttr(attr,
+                                diag::spi_attribute_on_frozen_stored_properties,
+                                VD->getName());
   }
 }
 

test/SPI/local_spi_decls.swift

@@ -31,7 +31,9 @@ func inlinable() -> SPIClass { // expected-error {{class 'SPIClass' is '@_spi' a
 @_spi(S) public struct SPIStruct {} // expected-note 2 {{struct 'SPIStruct' is not '@usableFromInline' or public}}
 
 @frozen public struct FrozenStruct {
-  @_spi(S) public var asdf = SPIStruct() // expected-error {{struct 'SPIStruct' is '@_spi' and cannot be referenced from a property initializer in a '@frozen' type}}
+  @_spi(S) public var spiInFrozen = SPIStruct() // expected-error {{struct 'SPIStruct' is '@_spi' and cannot be referenced from a property initializer in a '@frozen' type}}
+  // expected-error @-1 {{stored property 'spiInFrozen' cannot be declared '@_spi' in a '@frozen' struct}}
+
   var asdf = SPIStruct() // expected-error {{struct 'SPIStruct' is '@_spi' and cannot be referenced from a property initializer in a '@frozen' type}}
 }
 

test/SPI/resilience.swift

@@ -0,0 +1,29 @@
+// Test limits of SPI members in frozen types.
+
+// RUN: %target-typecheck-verify-swift
+
+@frozen
+public struct FrozenStruct {
+  public var okProperty: Int
+
+  @_spi(S)
+  public var okComputedProperty: Int { get { return 42 } }
+
+  @_spi(S) // expected-error {{stored property 'spiProperty' cannot be declared '@_spi' in a '@frozen' struct}}
+  public var spiProperty: Int
+
+  @_spi(S) // expected-error {{stored property 'spiPropertySet' cannot be declared '@_spi' in a '@frozen' struct}}
+  public var spiPropertySet = 4
+
+  @_spi(S) // expected-error {{stored property 'spiPropertyDoubleErrors' cannot be declared '@_spi' in a '@frozen' struct}}
+  // expected-error @-1 {{internal property cannot be declared '@_spi' because only public and open declarations can be '@_spi'}}
+  var spiPropertyDoubleErrors: Int
+}
+
+public struct UnfrozenStruct {
+  @_spi(S)
+  public var spiProperty: Int
+
+  @_spi(S)
+  public var spiPropertySet = 4
+}