Merge pull request swiftlang#32796 from xymus/fix-invalid-spi-attr-5.3

[5.3][ModuleInterface] Don't print SPI attributes on unsupported decls

Author: xymus

lib/AST/ASTPrinter.cpp

@@ -991,7 +991,9 @@ void PrintAST::printAttributes(const Decl *D) {
     }
 
     // SPI groups
-    if (Options.PrintSPIs) {
+    if (Options.PrintSPIs &&
+        DeclAttribute::canAttributeAppearOnDeclKind(
+          DAK_SPIAccessControl, D->getKind())) {
       interleave(D->getSPIGroups(),
              [&](Identifier spiName) {
                Printer.printAttrName("_spi", true);

test/SPI/private_swiftinterface.swift

@@ -88,6 +88,19 @@ private class PrivateClassLocal {}
   // CHECK-PUBLIC-NOT: extensionSPIMethod
 }
 
+@_spi(LocalSPI) public protocol SPIProto3 {
+// CHECK-PRIVATE: @_spi(LocalSPI) public protocol SPIProto3
+// CHECK-PUBLIC-NOT: SPIProto3
+
+  associatedtype AssociatedType
+  // CHECK-PRIVATE: {{^}}  associatedtype AssociatedType
+  // CHECK-PUBLIC-NOT: AssociatedType
+
+  func implicitSPIMethod()
+  // CHECK-PRIVATE: @_spi(LocalSPI) func implicitSPIMethod()
+  // CHECK-PUBLIC-NOT: implicitSPIMethod
+}
+
 // Test the dummy conformance printed to replace private types used in
 // conditional conformances. rdar://problem/63352700