[SILGen] Allow annotating self @_noImplicitCopy.

Allow @_noImplicitCopy to be applied to methods.  Applying it there
means that the self argument will have the attribute.

Author: nate-chandler

include/swift/AST/Attr.def

@@ -698,7 +698,7 @@ SIMPLE_DECL_ATTR(_noImplicitCopy, NoImplicitCopy,
   UserInaccessible |
   ABIStableToAdd | ABIBreakingToRemove |
   APIStableToAdd | APIBreakingToRemove |
-  OnParam | OnVar,
+  OnFunc | OnParam | OnVar,
   122)
 
 SIMPLE_DECL_ATTR(_noLocks, NoLocks,

lib/SILGen/SILGenProlog.cpp

@@ -360,6 +360,7 @@ struct ArgumentInitHelper {
     if (pd->isSelfParameter()) {
       if (auto *afd = dyn_cast<AbstractFunctionDecl>(pd->getDeclContext())) {
         lifetimeAnnotation = afd->getLifetimeAnnotation();
+        isNoImplicitCopy = afd->isNoImplicitCopy();
       }
     } else {
       lifetimeAnnotation = pd->getLifetimeAnnotation();

lib/Sema/TypeCheckAttr.cpp

@@ -343,6 +343,19 @@ void AttributeChecker::visitNoImplicitCopyAttr(NoImplicitCopyAttr *attr) {
     return;
   }
 
+  if (auto *funcDecl = dyn_cast<FuncDecl>(D)) {
+    if (visitLifetimeAttr(attr))
+      return;
+
+    // We only handle non-lvalue arguments today.
+    if (funcDecl->isMutating()) {
+      auto error = diag::noimplicitcopy_attr_valid_only_on_local_let_params;
+      diagnoseAndRemoveAttr(attr, error);
+      return;
+    }
+    return;
+  }
+
   auto *dc = D->getDeclContext();
 
   // If we have a param decl that is marked as no implicit copy, change our

test/SILGen/noimplicitcopy_attr.swift

@@ -18,3 +18,13 @@ public func arguments(@_noImplicitCopy _ x: Klass) {
 public func argumentsOwned(@_noImplicitCopy _ x: __owned Klass) {
     x.doSomething()
 }
+
+extension Klass {
+// CHECK-LABEL: sil hidden [ossa] @noimplicitcopy_method_attr : $@convention(method) (@owned Klass) -> () {
+// CHECK:       {{bb[0-9]+}}({{%[^,]+}} : @noImplicitCopy @owned $Klass):
+// CHECK-LABEL: } // end sil function 'noimplicitcopy_method_attr'
+  @_silgen_name("noimplicitcopy_method_attr")
+  @_noImplicitCopy
+  __consuming
+  func noimplicitcopy_method_attr() {}
+}

test/attr/noimplicitcopy.swift

@@ -0,0 +1,7 @@
+// RUN: %target-typecheck-verify-swift -enable-experimental-move-only
+
+struct S {
+  func bar(@_noImplicitCopy s: S) {} // okay
+  @_noImplicitCopy func foo(s: S) {} // okay
+  @_noImplicitCopy mutating func nopers() {} // expected-error {{'@_noImplicitCopy' attribute can only be applied to local lets and params}}
+}