AST: 'lazy' property initializers are never @inlinable

In @Frozen structs, stored properties and property wrappers must
have inlinable initial value expressions, since they are re-emitted
into designated initializer bodies, which themselves might be
@inlinable.

However, 'lazy' properties don't follow this pattern; the
initial value expression is emitted inside the getter, which
is never @inlinable.

Author: slavapestov

lib/AST/Decl.cpp

@@ -1582,6 +1582,11 @@ VarDecl *PatternBindingDecl::getAnchoringVarDecl(unsigned i) const {
 }
 
 bool VarDecl::isInitExposedToClients() const {
+  // 'lazy' initializers are emitted inside the getter, which is never
+  // @inlinable.
+  if (getAttrs().hasAttribute<LazyAttr>())
+    return false;
+
   return hasInitialValue() && isLayoutExposedToClients();
 }
 

test/SPI/spi_members.swift

@@ -47,8 +47,6 @@ public struct Resilient {
   @_spi(Foo) public lazy var lazyProperty2: Bar = Bar()
   // expected-error@-1 {{cannot use class 'Bar' here; it is SPI}}
   // expected-error@-2 {{stored property 'lazyProperty2' cannot be declared '@_spi' in a '@frozen' struct}}
-  // expected-error@-3 {{class 'Bar' cannot be used in a property initializer in a '@frozen' type because it is SPI}}
-  // expected-error@-4 {{initializer 'init()' cannot be used in a property initializer in a '@frozen' type because it is SPI}}
 
   @_spi(Foo) @Wrapper public var wrappedProperty1: Bar
   // expected-error@-1 {{stored property 'wrappedProperty1' cannot be declared '@_spi' in a '@frozen' struct}}
@@ -73,12 +71,8 @@ public struct Resilient {
   public var computedProperty: Bar { Bar() } // expected-error {{cannot use class 'Bar' here; it is SPI}}
 
   public lazy var lazyProperty1 = Bar() // expected-error {{cannot use class 'Bar' here; it is SPI}}
-  // expected-error@-1 {{initializer 'init()' cannot be used in a property initializer in a '@frozen' type because it is SPI}}
-  // expected-error@-2 {{class 'Bar' cannot be used in a property initializer in a '@frozen' type because it is SPI}}
 
   public lazy var lazyProperty2: Bar = Bar() // expected-error {{cannot use class 'Bar' here; it is SPI}}
-  // expected-error@-1 {{initializer 'init()' cannot be used in a property initializer in a '@frozen' type because it is SPI}}
-  // expected-error@-2 {{class 'Bar' cannot be used in a property initializer in a '@frozen' type because it is SPI}}
 
   @Wrapper public var wrappedProperty1: Bar
   // expected-error@-1 {{cannot use class 'Bar' here; it is SPI}}
@@ -105,12 +99,8 @@ public struct Resilient {
   private var computedProperty: Bar { Bar() }
 
   private lazy var lazyProperty1 = Bar() // expected-error {{cannot use class 'Bar' here; it is SPI}}
-  // expected-error@-1 {{initializer 'init()' cannot be used in a property initializer in a '@frozen' type because it is SPI}}
-  // expected-error@-2 {{class 'Bar' cannot be used in a property initializer in a '@frozen' type because it is SPI}}
 
   private lazy var lazyProperty2: Bar = Bar() // expected-error {{cannot use class 'Bar' here; it is SPI}}
-  // expected-error@-1 {{initializer 'init()' cannot be used in a property initializer in a '@frozen' type because it is SPI}}
-  // expected-error@-2 {{class 'Bar' cannot be used in a property initializer in a '@frozen' type because it is SPI}}
 
   @Wrapper private var wrappedProperty1: Bar
   // expected-error@-1 {{cannot use class 'Bar' here; it is SPI}}

test/attr/attr_inlinable.swift

@@ -340,3 +340,13 @@ public struct PrivateInlinableCrash {
 
   func innerFunction4(x: () = publicFunction()) {}
 }
+
+// This is OK -- lazy property initializers are emitted inside the getter,
+// which is never @inlinable.
+@frozen public struct LazyField {
+  public lazy var y: () = privateFunction()
+
+  @inlinable private lazy var z: () = privateFunction()
+  // expected-error@-1 {{'@inlinable' attribute cannot be applied to stored properties}}
+}
+