shader-clippy

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mesh-node-not-leaf ​

Pre-v0 status: this rule page is published ahead of the implementation (preview / experimental, gated behind [experimental] work-graph-mesh-nodes = true in .shader-clippy.toml). Behaviour described here reflects the design intent; the preview API may change.

(via ADR 0010)

What it detects ​

A work-graph mesh node (a node with [NodeLaunch("mesh")]) that has any outgoing NodeOutput<...> declarations. The Mesh Nodes in Work Graphs preview specification requires mesh nodes to be leaf nodes — they consume input records but produce only rasterized output. Slang reflection identifies the node-launch kind and the output declarations; the rule fires when both coexist.

Why it matters on a GPU ​

Mesh nodes integrate the mesh-shader pipeline into work graphs: a node receives input records from upstream nodes and emits vertices / primitives to the rasterizer rather than records to a downstream node. On NVIDIA Ada Lovelace and AMD RDNA 3 (the IHVs initially supporting the preview API), the runtime schedules mesh nodes against the rasterizer's input queue exactly as DispatchMesh does, but with the work-graph dispatch arguments standing in for the application's DispatchMesh arguments.

The leaf-only constraint exists because the runtime has no mechanism to forward records from a mesh node to a downstream work-graph node — the mesh node's output goes to the rasterizer, period. Allowing mesh nodes to declare NodeOutput<...> would require a brand-new path through the scheduler that does not exist in the current preview implementations and is not in the spec.

The current preview driver path produces a hard PSO-link error when the constraint is violated; spec-status discipline (per ADR 0010) keeps the rule behind an experimental.work-graph-mesh-nodes flag because the preview API may change. The diagnostic names the offending output declaration so the author can move it to a non-mesh node or remove it.

Examples ​

Bad ​

hlsl
// Mesh node with NodeOutput — leaf-only constraint violated.
struct Record { uint payload; };

[Shader("node")]
[NodeLaunch("mesh")]
[NodeDispatchGrid(64, 1, 1)]
[numthreads(64, 1, 1)]
[outputtopology("triangle")]
void MeshNode(
    [MaxRecords(64)] DispatchNodeInputRecord<Record> in,
    [MaxRecords(64)] NodeOutput<Record>             downstream, // ERROR: leaf-only
    out vertices Vertex   verts[64],
    out indices  uint3    tris[124])
{
    /* ... */
}

Good ​

hlsl
// Mesh node has no NodeOutput; downstream work goes through a separate node.
[Shader("node")]
[NodeLaunch("mesh")]
[NodeDispatchGrid(64, 1, 1)]
[numthreads(64, 1, 1)]
[outputtopology("triangle")]
void MeshNode(
    [MaxRecords(64)] DispatchNodeInputRecord<Record> in,
    out vertices Vertex   verts[64],
    out indices  uint3    tris[124])
{
    /* ... */
}

Options ​

This rule is gated behind [experimental] work-graph-mesh-nodes = true in .shader-clippy.toml. With the gate off, the rule does not fire.

Fix availability ​

none — Removing the output declaration changes the work-graph topology; the diagnostic names the offending field.

See also ​

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© 2026 NelCit — Apache-2.0 (code), CC-BY-4.0 (docs).