Document the @noescape SIL function type attribute.

[atrick]

No description provided.

[aschwaighofer]

This predates @noescape. @convention(block)'s context is passed unowned

From test/IRGen/objc_block.sil:

// CHECK-LABEL: define{{( protected)?}} swiftcc %T10objc_block3FooC* @call_block(%objc_block*, %T10objc_block3FooC*) {{.*}} {
// CHECK:       entry:
// CHECK:         [[T0:%.*]] = getelementptr inbounds %objc_block, %objc_block* %0, i32 0, i32 3
// CHECK:         [[T1:%.*]] = load i8*, i8** [[T0]]
// CHECK:         [[T2:%.*]] = bitcast i8* [[T1]] to i8* (%objc_block*, i8*)*
// CHECK:         [[T3:%.*]] = bitcast %T10objc_block3FooC* %1 to i8*
// CHECK:         [[T4:%.*]] = call i8* [[T2]](%objc_block* %0, i8* [[T3]])
// CHECK:         [[T5:%.*]] = bitcast i8* [[T4]] to %T10objc_block3FooC*
// CHECK:         ret %T10objc_block3FooC* [[T5]]
// CHECK:       }

[atrick]

@aschwaighofer is it fair to say that @callee_x attribute implies @convention(thick) attribute?

[aschwaighofer]

It only makes sense to have an ownership qualifier for the context on a function representation that has a context. Yes I think so.

[aschwaighofer]

We can have:

• @convention(thin) () -> ()
  No context, can be converted to a @convention(thin) @NoEscape type.

• @convention(block) () -> ()
  Objective-C block convention; context is passed @unowned in spirit.

• Thick swift function types: @callee_guaranteed () -> ()
  Can be @NoEscape in which case the context value is treated as a trivial type -- which admittedly is a little odd because we still spell out ownership (which we usually only do for reference counted things).
  @callee_owned is dead.

[atrick]

@aschwaighofer here's another revision. I'll let you figure out how to kill off @callee_owned. It's still all over the tests and handled in ParseDecl.cpp.

[aschwaighofer]

This looks good to me.

[atrick]

@swift-ci smoke test and merge.

[atrick]

@swift-ci smoke test and merge.