From 576723960e482c81bb710de7b3604890fe6d0c47 Mon Sep 17 00:00:00 2001
From: Jim Blandy <jimb@red-bean.com>
Date: Thu, 15 Apr 2021 12:14:48 -0700
Subject: [PATCH] Permit interpolation qualifiers on both vertex outputs and
 fragment inputs.

---
 src/valid/interface.rs | 7 +++++--
 1 file changed, 5 insertions(+), 2 deletions(-)

diff --git a/src/valid/interface.rs b/src/valid/interface.rs
index 17629d1e08..1299b38216 100644
--- a/src/valid/interface.rs
+++ b/src/valid/interface.rs
@@ -210,8 +210,11 @@ impl VaryingContext<'_> {
                 if !self.location_mask.insert(location as usize) {
                     return Err(VaryingError::BindingCollision { location });
                 }
-                let needs_interpolation =
-                    self.stage == crate::ShaderStage::Fragment && !self.output;
+                let needs_interpolation = match self.stage {
+                    crate::ShaderStage::Vertex => self.output,
+                    crate::ShaderStage::Fragment => !self.output,
+                    _ => false,
+                };
                 if !needs_interpolation && interpolation.is_some() {
                     return Err(VaryingError::InvalidInterpolation);
                 }