[Sema] Ban @_eagerMove on Copyable things.

Author: nate-chandler

include/swift/AST/DiagnosticsSema.def

@@ -3520,6 +3520,8 @@ ERROR(lifetime_invalid_global_scope,none, "%0 is only valid on methods",
 ERROR(eagermove_and_lexical_combined,none,
       "@_eagerMove and @_noEagerMove attributes are alternate styles of lifetimes "
       "and can't be combined", ())
+ERROR(eagermove_and_noncopyable_combined,none,
+      "@_eagerMove cannot be applied to NonCopyable types", ())
 
 ERROR(autoclosure_function_type,none,
       "@autoclosure attribute only applies to function types",

lib/Sema/TypeCheckAttr.cpp

@@ -6878,6 +6878,25 @@ bool AttributeChecker::visitLifetimeAttr(DeclAttribute *attr) {
 void AttributeChecker::visitEagerMoveAttr(EagerMoveAttr *attr) {
   if (visitLifetimeAttr(attr))
     return;
+  if (auto *nominal = dyn_cast<NominalTypeDecl>(D)) {
+    if (nominal->getDeclaredInterfaceType()->isPureMoveOnly()) {
+      diagnoseAndRemoveAttr(attr, diag::eagermove_and_noncopyable_combined);
+      return;
+    }
+  }
+  if (auto *func = dyn_cast<FuncDecl>(D)) {
+    auto *self = func->getImplicitSelfDecl();
+    if (self && self->getType()->isPureMoveOnly()) {
+      diagnoseAndRemoveAttr(attr, diag::eagermove_and_noncopyable_combined);
+      return;
+    }
+  }
+  if (auto *pd = dyn_cast<ParamDecl>(D)) {
+    if (pd->getType()->isPureMoveOnly()) {
+      diagnoseAndRemoveAttr(attr, diag::eagermove_and_noncopyable_combined);
+      return;
+    }
+  }
 }
 
 void AttributeChecker::visitNoEagerMoveAttr(NoEagerMoveAttr *attr) {

test/attr/lexical.swift

@@ -43,3 +43,16 @@ func foo() {
   _ = s2
   _ = s3
 }
+
+@_moveOnly struct MoveOnly {}
+
+@_eagerMove @_moveOnly struct MoveOnlyEagerly {} // expected-error {{@_eagerMove cannot be applied to NonCopyable types}}
+
+func zoo(@_eagerMove _ : consuming MoveOnly) {} // expected-error {{@_eagerMove cannot be applied to NonCopyable types}}
+
+func zooo(@_noEagerMove  _ : consuming C) {} // ok, only way to spell this behavior
+
+extension MoveOnly {
+  @_eagerMove // expected-error {{@_eagerMove cannot be applied to NonCopyable types}}
+  func zoo() {}
+}