[glsl-in] fix swizzle in a global const context

naga/src/front/glsl/context.rs

@@ -1478,7 +1478,11 @@ impl Index<Handle<Expression>> for Context<'_> {
     type Output = Expression;
 
     fn index(&self, index: Handle<Expression>) -> &Self::Output {
-        &self.expressions[index]
+        if self.is_const {
+            &self.module.const_expressions[index]
+        } else {
+            &self.expressions[index]
+        }
     }
 }
 

naga/tests/in/glsl/const-global-swizzle.frag

@@ -0,0 +1,15 @@
+// ISSUE: #4773
+#version 450
+
+#define MIX2(c) c.xy
+
+layout(location = 0) in vec2 v_Uv;
+
+layout(location = 0) out vec4 o_Target;
+
+const vec2 blank = MIX2(vec2(0.0, 1.0));
+
+void main() {
+    vec2 col = MIX2(v_Uv) * blank;
+    o_Target = vec4(col, 0.0, 1.0);
+}

naga/tests/out/wgsl/const-global-swizzle.frag.wgsl

@@ -0,0 +1,26 @@
+struct FragmentOutput {
+    @location(0) o_Target: vec4<f32>,
+}
+
+const blank: vec2<f32> = vec2<f32>(0f, 1f);
+
+var<private> v_Uv_1: vec2<f32>;
+var<private> o_Target: vec4<f32>;
+
+fn main_1() {
+    var col: vec2<f32>;
+
+    let _e3 = v_Uv_1;
+    col = (_e3.xy * blank);
+    let _e7 = col;
+    o_Target = vec4<f32>(_e7.x, _e7.y, 0f, 1f);
+    return;
+}
+
+@fragment 
+fn main(@location(0) v_Uv: vec2<f32>) -> FragmentOutput {
+    v_Uv_1 = v_Uv;
+    main_1();
+    let _e9 = o_Target;
+    return FragmentOutput(_e9);
+}