[noimplicitcopy] Error if a noimplicitcopy vardecl or paramdecl is of move only type.

rdar://104934156

Author: gottesmm

include/swift/AST/DiagnosticsSema.def

@@ -6648,6 +6648,8 @@ ERROR(noimplicitcopy_attr_valid_only_on_local_let_params,
       none, "'@_noImplicitCopy' attribute can only be applied to local lets and params", ())
 ERROR(noimplicitcopy_attr_invalid_in_generic_context,
       none, "'@_noImplicitCopy' attribute cannot be applied to entities in generic contexts", ())
+ERROR(noimplicitcopy_attr_not_allowed_on_moveonlytype,none,
+      "'@_noImplicitCopy' has no effect when applied to a move only type", ())
 
 //------------------------------------------------------------------------------
 // MARK: Type inference from default expressions

lib/Sema/TypeCheckDeclPrimary.cpp

@@ -32,6 +32,7 @@
 #include "swift/AST/ASTWalker.h"
 #include "swift/AST/AccessNotes.h"
 #include "swift/AST/AccessScope.h"
+#include "swift/AST/Attr.h"
 #include "swift/AST/Decl.h"
 #include "swift/AST/DeclContext.h"
 #include "swift/AST/DiagnosticsSema.h"
@@ -2184,6 +2185,21 @@ class DeclChecker : public DeclVisitor<DeclChecker> {
     VD->visitEmittedAccessors([&](AccessorDecl *accessor) {
       visit(accessor);
     });
+
+    // If this var decl is a no implicit copy varDecl, error if its type is a
+    // move only type. No implicit copy is redundant.
+    //
+    // NOTE: We do this here instead of TypeCheckAttr since types are not
+    // completely type checked at that point.
+    if (auto attr = VD->getAttrs().getAttribute<NoImplicitCopyAttr>()) {
+      if (auto *nom = VD->getType()->getCanonicalType()->getNominalOrBoundGenericNominal()) {
+        if (nom->isMoveOnly()) {
+          DE.diagnose(attr->getLocation(),
+                      diag::noimplicitcopy_attr_not_allowed_on_moveonlytype)
+            .fixItRemove(attr->getRange());
+        }
+      }
+    }
   }
 
   void visitPatternBindingDecl(PatternBindingDecl *PBD) {
@@ -3657,6 +3673,17 @@ void TypeChecker::checkParameterList(ParameterList *params,
           DeclChecker(param->getASTContext(), SF).visitBoundVariable(auxiliaryDecl);
       });
     }
+
+    // If we have a noimplicitcopy parameter, make sure that the underlying type
+    // is not move only. It is redundant.
+    if (auto attr = param->getAttrs().getAttribute<NoImplicitCopyAttr>()) {
+      if (auto *nom = param->getType()->getCanonicalType()->getNominalOrBoundGenericNominal()) {
+        if (nom->isMoveOnly()) {
+          param->diagnose(diag::noimplicitcopy_attr_not_allowed_on_moveonlytype)
+            .fixItRemove(attr->getRange());
+        }
+      }
+    }
   }
 
   // For source compatibility, allow duplicate internal parameter names

test/Sema/noimplicitcopy_attr.swift

@@ -138,3 +138,17 @@ func useGeneric<T>(_ x: T) {
     let z = y
     print(z)
 }
+
+@_moveOnly
+struct MoveOnly {
+    var k = Klass()
+}
+
+func useMoveOnly(@_noImplicitCopy _ x: MoveOnly) -> MoveOnly { // expected-error {{'@_noImplicitCopy' has no effect when applied to a move only type}}
+    return x
+}
+
+func useMoveOnly2(_ x: MoveOnly) {
+    @_noImplicitCopy let y = x // expected-error {{'@_noImplicitCopy' has no effect when applied to a move only type}}
+    let _ = y
+}