slang-associatedtype-shadowing-builtin

Status: shipped (Phase 8.C — ADR 0021 sub-phase C, v1.5.0).

What it detects

An associatedtype X; declaration inside an interface_specifier body whose name X collides with a built-in HLSL/Slang type name. The rule walks the tree-sitter-slang AST looking for associatedtype_declaration nodes (the grammar's exact node-kind, NOT the prompt-predicted associatedtype_declaration shape — they happen to match). The first type_identifier child carries the associated type's name; the rule checks it against a built-in vocabulary including the scalar primitive types (bool, int, uint, float, double, half, min16float, etc.), the common vector shorthand families (float2, float3, float4, ...), the texture surfaces (Texture2D, Texture3D, TextureCube, ...), the buffer surfaces (Buffer, StructuredBuffer, RWBuffer, ByteAddressBuffer, ...), and the sampler / acceleration-structure types.

Why it matters on a GPU

This is a name-resolution footgun that costs correctness, not performance. Inside an interface scope, Slang's name resolution prefers the abstract associated type over the surrounding built-in type. So a function body inside the interface that references Texture2D implicitly binds to the abstract associated type — every call to Texture2D::Sample etc. routes through a witness table lookup at specialisation time, and the developer's intent ("I want HLSL's concrete Texture2D here") is silently discarded.

The fix is always to rename the associated type. The cost is exactly two characters of extra typing (e.g. Tex2D instead of Texture2D) and a much clearer reading of what the interface actually requires of its conformers.

Examples

Bad

interface IBad {
    // Inside this interface, `Texture2D` no longer means the HLSL
    // built-in -- it means "whatever concrete type the conformer
    // chooses to substitute". Subtle and silent.
    associatedtype Texture2D;
}

Good

interface IGood {
    // Different name -- no shadowing. References to `Texture2D`
    // inside the interface body still mean the HLSL built-in.
    associatedtype Tex;
}

Options

none

Fix availability

none — picking a non-shadowing name requires developer intent. The diagnostic suggests renaming.

See also

• Companion blog post: link to the relevant per-category overview under ../blog/slang-language-overview.md if one exists; otherwise leave as not yet published until a per-rule post lands.

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