Validate shader location clashes (#3613)

* Validate shader location clashes

* Add line to changelog

CHANGELOG.md

@@ -150,6 +150,7 @@ By @cwfitzgerald in [#3610](https://github.com/gfx-rs/wgpu/pull/3610).
 - `copyTextureToTexture` src/dst aspects must both refer to all aspects of src/dst format. By @teoxoy in [#3431](https://github.com/gfx-rs/wgpu/pull/3431)
 - Validate before extracting texture selectors. By @teoxoy in [#3487](https://github.com/gfx-rs/wgpu/pull/3487)
 - Fix fatal errors (those which panic even if an error handler is set) not including all of the details. By @kpreid in [#3563](https://github.com/gfx-rs/wgpu/pull/3563)
+- Validate shader location clashes. By @emilk in [#3613](https://github.com/gfx-rs/wgpu/pull/3613)
 
 #### Vulkan
 

wgpu-core/src/device/mod.rs

@@ -2806,10 +2806,16 @@ impl<A: HalApi> Device<A> {
                     self.require_features(wgt::Features::VERTEX_ATTRIBUTE_64BIT)?;
                 }
 
-                io.insert(
+                let previous = io.insert(
                     attribute.shader_location,
                     validation::InterfaceVar::vertex_attribute(attribute.format),
                 );
+
+                if previous.is_some() {
+                    return Err(pipeline::CreateRenderPipelineError::ShaderLocationClash(
+                        attribute.shader_location,
+                    ));
+                }
             }
             total_attributes += vb_state.attributes.len();
         }

wgpu-core/src/pipeline.rs

@@ -352,6 +352,8 @@ pub enum CreateRenderPipelineError {
         location: wgt::ShaderLocation,
         offset: wgt::BufferAddress,
     },
+    #[error("Two or more attributes were assigned to the same shader lcoation {0}")]
+    ShaderLocationClash(u32),
     #[error("Strip index format was not set to None but to {strip_index_format:?} while using the non-strip topology {topology:?}")]
     StripIndexFormatForNonStripTopology {
         strip_index_format: Option<wgt::IndexFormat>,