Shader packs: struct types without a name

GLSL lets a declaration define its struct type in place without naming it
(GLSL 4.60, 4.1.8): `shared struct { uint sum; uint tile[8][8]; } lds;`.
naga's frontend wants a name ("Expected identifier, found LeftBrace"), which
RenderPearl v2.7.2's compute programs (deferred, deferred1, composite,
composite3) hit. Each such type now gets one (`hz_struct<n>`) before the
stages are read.

Part of #7171

Co-Authored-By: Claude Opus 5.5 <[email protected]>

crates/horizon-shaders/src/translate/anonymous_structs.rs

@@ -0,0 +1,44 @@
+//! Struct types without a name. GLSL lets a declaration define its struct type in place without
+//! naming it (GLSL 4.60, 4.1.8: `shared struct { uint sum; uint tile[64]; } lds;`); naga's
+//! frontend wants a name there ("Expected identifier, found LeftBrace"). Each such type gets
+//! one, `hz_struct<n>`; nothing else changes.
+
+use super::scan::significant;
+use crate::macros::lex;
+
+/// `code` with a name for each struct type declared without one, or `None` when it has none.
+pub(super) fn name(code: &str) -> Option<String> {
+    let tokens = lex(code);
+    let mut out = String::with_capacity(code.len() + 64);
+    let mut named = 0;
+    for (i, t) in tokens.iter().enumerate() {
+        out.push_str(t);
+        let opens = (i + 1..tokens.len())
+            .find(|&j| significant(tokens[j]))
+            .is_some_and(|j| tokens[j] == "{");
+        if *t == "struct" && opens {
+            out.push_str(&format!(" hz_struct{named}"));
+            named += 1;
+        }
+    }
+    (named > 0).then_some(out)
+}
+
+#[cfg(test)]
+mod tests {
+    use super::name;
+
+    #[test]
+    fn struct_types_without_a_name_get_one() {
+        let code = "shared struct {\n    uint sum;\n} lds;\nstruct Light { vec3 c; };\n\
+                    struct\n{ float a; } x, y[2];\n";
+        assert_eq!(
+            name(code).as_deref(),
+            Some(
+                "shared struct hz_struct0 {\n    uint sum;\n} lds;\nstruct Light { vec3 c; };\n\
+                 struct hz_struct1\n{ float a; } x, y[2];\n"
+            )
+        );
+        assert_eq!(name("struct Light { vec3 c; };\n"), None);
+    }
+}

crates/horizon-shaders/src/translate/mod.rs

@@ -27,6 +27,7 @@ use naga::valid::{Capabilities, ValidationFlags, Validator};
 
 use crate::Preprocessed;
 
+mod anonymous_structs;
 mod atomic_vectors;
 mod geometry;
 mod image_parameters;
@@ -239,9 +240,14 @@ fn translate(
     } else {
         GBUFFERS_MATRICES.to_owned()
     };
-    // Interface blocks travel as plain varyings (`interface_blocks`).
+    // Struct types without a name get one (`anonymous_structs`), and interface blocks travel
+    // as plain varyings (`interface_blocks`).
     let flat = |pp: &Preprocessed| {
-        interface_blocks::flatten(&pp.code).map(|code| Preprocessed { code, ..pp.clone() })
+        let named = anonymous_structs::name(&pp.code);
+        let code = named.as_deref().unwrap_or(&pp.code);
+        interface_blocks::flatten(code)
+            .or(named)
+            .map(|code| Preprocessed { code, ..pp.clone() })
     };
     let (vertex_flat, fragment_flat) = (flat(vertex), flat(fragment));
     let vertex = vertex_flat.as_ref().unwrap_or(vertex);
@@ -625,6 +631,11 @@ fn resources(
 
 /// Translates a compute program (`.csh`).
 pub fn translate_compute(compute: &Preprocessed) -> Result<ComputeProgram, Vec<Error>> {
+    let named = anonymous_structs::name(&compute.code).map(|code| Preprocessed {
+        code,
+        ..compute.clone()
+    });
+    let compute = named.as_ref().unwrap_or(compute);
     let split = atomic_vectors::rewrite(compute);
     let compute = split.as_ref().unwrap_or(compute);
     let mut c = Stage::scan(compute, ShaderStage::Compute);
@@ -2157,6 +2168,20 @@ mod tests {
         }));
     }
 
+    /// A `shared` variable whose struct type has no name (GLSL 4.60, 4.1.8), as compute
+    /// programs keep their work group's tiles.
+    #[test]
+    fn a_shared_struct_without_a_type_name_compiles() {
+        let csh = "#version 460\nlayout(local_size_x = 8, local_size_y = 8) in;\n\
+                   shared struct {\n    uint sum;\n    uint tile[gl_WorkGroupSize.x][gl_WorkGroupSize.y];\n} lds;\n\
+                   layout(r32ui) uniform uimage2D colorimg4;\nvoid main() {\n    \
+                   lds.tile[gl_LocalInvocationID.x][gl_LocalInvocationID.y] = gl_LocalInvocationIndex;\n    \
+                   barrier();\n    imageStore(colorimg4, ivec2(gl_GlobalInvocationID.xy), uvec4(lds.tile[1][1]));\n}\n";
+        let pack = Pack::from_zip_bytes("P.zip", zip(&[("shaders/deferred_a.csh", csh)])).unwrap();
+        translate_compute(&preprocess(&pack, "deferred_a.csh", &Macros::standard()))
+            .unwrap_or_else(|e| panic!("{e:?}"));
+    }
+
     #[test]
     fn buffer_blocks_bind_at_their_binding() {
         let csh = "#version 430\nlayout(local_size_x = 1) in;\n\