Vx

E6015

Error · Topology/Hardware

E6015 — A structurally invalid transfer lowering (impl transfer A -> B { ... }): the same edge implemented twice in one compilation (which one is in force would be load order), or a lowering with no functions (an empty body cannot move anything, and accepting it would make impl transfer an inert annotation rather than code).

What the compiler reports

E6015
declares no functions

The fragments the test suite holds the compiler to. An ellipsis marks text the test does not constrain; the emitted message also carries a source location.

A program that triggers it

// An empty lowering cannot move anything; accepting it would make `impl transfer` an
// inert annotation rather than code (Vx#352).
Topology Dev {
  memory: Memory::L2,
  visible: [Memory::L2, Memory::SMEM],
  transfer Memory::CPU_DRAM -> Memory::L2 : 10 GB/s,
  transfer Memory::L2 -> Memory::SMEM
}
impl Transfer<Memory::L2, Memory::SMEM> for Topology::Dev {
}
fn main() -> i32 {
  return 0;
}

From tests/middle_end/fail/transfer_impl_empty.vx, which asserts this diagnostic on every commit.

Related

Topologies and memoryThe chapter covering the rule this code enforces. All diagnosticsEvery code the compiler can emit, grouped by stage. E6014A program stages through host memory while a machine model is in force, and no host was declared. --machine describes an accelerator and says nothing about the machine it hangs off, so the host end of that seam was being reasoned about without anything describing it. --host <file> names one; --host default names the machine compiling the program. A host declares no capacity — host memory is virtual, and a hard limit would reject programs that page rather than fail — so this is about the host being *stated* rather than assumed, not about a budget. E6016A Topology or Memory declaration whose identity cannot be relied on. Two forms: the declared name shadows a built-in topology (every use of Topology::<Name> resolves to the built-in, so the declaration is silently ignored — including its arch:); or two declared names collide on one dispatch id (custom ids are derived from the name by hashing), in which case which declaration is in force would be hash-iteration order — observed as the same program getting a device image on some runs and not others for a topology, and as a transfer carrying the other space's capacity and granule for a memory space.