[naga] Make additional test code reachable from entrypoints

naga/tests/in/glsl/declarations.frag

@@ -35,5 +35,6 @@ void main() {
     const vec4 from_input_array = in_array[1];
     const float a = array_2d[0][0];
     const float b = array_toomanyd[0][0][0][0][0][0][0];
+    const LightScatteringParams light_scattering_params;
     out_array[0] = vec4(2.0);
 }

naga/tests/naga/wgsl_errors.rs

@@ -2861,7 +2861,12 @@ fn compaction_preserves_spans() {
            var x: array<i32,1>;
            var y = x[1.0];
         }
-    "#; //         ^^^   correct error span: 108..114
+        @compute @workgroup_size(1)
+        fn main() {
+            f();
+        }
+    "#;
+    // The error span should be on `x[1.0]`, which is at characters 108..114.
     let mut module = naga::front::wgsl::parse_str(source).expect("source ought to parse");
     naga::compact::compact(&mut module);
     let err = naga::valid::Validator::new(
@@ -2878,7 +2883,7 @@ fn compaction_preserves_spans() {
     // The first span is the whole function.
     let _ = spans.next().expect("error should have at least one span");
 
-    // The second span is the assignment destination.
+    // The second span is the invalid indexing expression.
     let dest_span = spans
         .next()
         .expect("error should have at least two spans")

naga/tests/out/wgsl/glsl-declarations.frag.wgsl

@@ -43,6 +43,7 @@ fn main_1() {
     var from_input_array: vec4<f32>;
     var a_1: f32;
     var b: f32;
+    var light_scattering_params: LightScatteringParams;
 
     let _e17 = in_array_2[1];
     from_input_array = _e17;