[Impeller] added static check that fragment shader and vertex shaders slots match

ci/licenses_golden/licenses_flutter

@@ -40715,6 +40715,7 @@ ORIGIN: ../../../flutter/impeller/renderer/shader_key.cc + ../../../flutter/LICE
 ORIGIN: ../../../flutter/impeller/renderer/shader_key.h + ../../../flutter/LICENSE
 ORIGIN: ../../../flutter/impeller/renderer/shader_library.cc + ../../../flutter/LICENSE
 ORIGIN: ../../../flutter/impeller/renderer/shader_library.h + ../../../flutter/LICENSE
+ORIGIN: ../../../flutter/impeller/renderer/shader_stage_compatibility_checker.h + ../../../flutter/LICENSE
 ORIGIN: ../../../flutter/impeller/renderer/snapshot.cc + ../../../flutter/LICENSE
 ORIGIN: ../../../flutter/impeller/renderer/snapshot.h + ../../../flutter/LICENSE
 ORIGIN: ../../../flutter/impeller/renderer/stroke.comp + ../../../flutter/LICENSE
@@ -43596,6 +43597,7 @@ FILE: ../../../flutter/impeller/renderer/shader_key.cc
 FILE: ../../../flutter/impeller/renderer/shader_key.h
 FILE: ../../../flutter/impeller/renderer/shader_library.cc
 FILE: ../../../flutter/impeller/renderer/shader_library.h
+FILE: ../../../flutter/impeller/renderer/shader_stage_compatibility_checker.h
 FILE: ../../../flutter/impeller/renderer/snapshot.cc
 FILE: ../../../flutter/impeller/renderer/snapshot.h
 FILE: ../../../flutter/impeller/renderer/stroke.comp

impeller/renderer/pipeline.h

@@ -13,6 +13,7 @@
 #include "impeller/renderer/context.h"
 #include "impeller/renderer/pipeline_builder.h"
 #include "impeller/renderer/pipeline_descriptor.h"
+#include "impeller/renderer/shader_stage_compatibility_checker.h"
 
 namespace impeller {
 
@@ -89,6 +90,11 @@ PipelineFuture<ComputePipelineDescriptor> CreatePipelineFuture(
 
 template <class VertexShader_, class FragmentShader_>
 class RenderPipelineT {
+  static_assert(
+      ShaderStageCompatibilityChecker<VertexShader_, FragmentShader_>::Check(),
+      "The output slots for the fragment shader don't have matches in the "
+      "vertex shader's output slots. This will result in a linker error.");
+
  public:
   using VertexShader = VertexShader_;
   using FragmentShader = FragmentShader_;

impeller/renderer/shader_stage_compatibility_checker.h

@@ -0,0 +1,76 @@
+// Copyright 2013 The Flutter Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef FLUTTER_IMPELLER_RENDERER_SHADER_STAGE_COMPATIBILITY_CHECKER_H_
+#define FLUTTER_IMPELLER_RENDERER_SHADER_STAGE_COMPATIBILITY_CHECKER_H_
+
+namespace impeller {
+/// This is a classed use to check that the input slots of fragment shaders
+/// match the output slots of the vertex shaders.
+/// If they don't match it will result in linker errors when creating the
+/// pipeline.  It's not used at runtime.
+template <typename VertexShaderT, typename FragmentShaderT>
+class ShaderStageCompatibilityChecker {
+ public:
+  static constexpr bool CompileTimeStrEqual(const char* str1,
+                                            const char* str2) {
+    return *str1 == *str2 &&
+           (*str1 == '\0' || CompileTimeStrEqual(str1 + 1, str2 + 1));
+  }
+
+  /// Returns `true` if the shader input slots for the fragment shader match the
+  /// ones declared as outputs in the vertex shader.
+  static constexpr bool Check() {
+    constexpr size_t num_outputs = VertexShaderT::kAllShaderStageOutputs.size();
+    constexpr size_t num_inputs = FragmentShaderT::kAllShaderStageInputs.size();
+
+    if (num_inputs > num_outputs) {
+      return false;
+    }
+
+    for (size_t i = 0; i < num_inputs; ++i) {
+      const ShaderStageIOSlot* input_slot =
+          FragmentShaderT::kAllShaderStageInputs[i];
+      for (size_t j = 0; j < num_outputs; ++j) {
+        const ShaderStageIOSlot* output_slot =
+            VertexShaderT::kAllShaderStageOutputs[j];
+        if (input_slot->location == output_slot->location) {
+          if (!CompileTimeStrEqual(input_slot->name, output_slot->name) ||
+              input_slot->set != output_slot->set ||
+              input_slot->binding != output_slot->binding ||
+              input_slot->type != output_slot->type ||
+              input_slot->bit_width != output_slot->bit_width ||
+              input_slot->vec_size != output_slot->vec_size ||
+              input_slot->columns != output_slot->columns ||
+              input_slot->offset != output_slot->offset) {
+            return false;
+          }
+        }
+      }
+    }
+
+    return true;
+  }
+};
+
+// The following shaders don't define output slots.
+// TODO(https://github.com/flutter/flutter/issues/146852): Make impellerc emit
+// an empty array for output slots.
+struct CheckerboardVertexShader;
+struct ClipVertexShader;
+
+template <typename FragmentShaderT>
+class ShaderStageCompatibilityChecker<CheckerboardVertexShader,
+                                      FragmentShaderT> {
+ public:
+  static constexpr bool Check() { return true; }
+};
+
+template <typename FragmentShaderT>
+class ShaderStageCompatibilityChecker<ClipVertexShader, FragmentShaderT> {
+ public:
+  static constexpr bool Check() { return true; }
+};
+}  // namespace impeller
+#endif  // FLUTTER_IMPELLER_RENDERER_SHADER_STAGE_COMPATIBILITY_CHECKER_H_