semantic::Function: Clean up ReferencedXXX() return types

Use a type alias for the most common and lengthy return type.

Drop the `const` from the return type - it is (or at least should be) meaningless.

Fix `auto& referenced_variables =` local variable declaration in inspector.cc.
You cannot take a reference to a non-ref return value of a function.
I have no idea why the compiler wasn't erroring about this.

Change-Id: Icc0b4a9bf4b4c9d03b44670eda27214ef04ad41c
Reviewed-on: https://dawn-review.googlesource.com/c/tint/+/42021
Commit-Queue: Ben Clayton <bclayton@google.com>
Reviewed-by: dan sinclair <dsinclair@chromium.org>
Reviewed-by: Ryan Harrison <rharrison@chromium.org>

src/inspector/inspector.cc

@@ -412,7 +412,7 @@ std::vector<ResourceBinding> Inspector::GetSampledTextureResourceBindingsImpl(
 
   std::vector<ResourceBinding> result;
   auto* func_sem = program_->Sem().Get(func);
-  auto& referenced_variables =
+  auto referenced_variables =
       multisampled_only ? func_sem->ReferencedMultisampledTextureVariables()
                         : func_sem->ReferencedSampledTextureVariables();
   for (auto& ref : referenced_variables) {

src/semantic/function.h

@@ -47,6 +47,9 @@ class Function : public Castable<Function, CallTarget> {
     ast::GroupDecoration* group = nullptr;
   };
 
+  /// A vector of [Variable*, BindingInfo] pairs
+  using VariableBindings = std::vector<std::pair<const Variable*, BindingInfo>>;
+
   /// Constructor
   /// @param declaration the ast::Function
   /// @param referenced_module_vars the referenced module variables
@@ -80,59 +83,52 @@ class Function : public Castable<Function, CallTarget> {
   }
   /// Retrieves any referenced location variables
   /// @returns the <variable, decoration> pair.
-  const std::vector<std::pair<const Variable*, ast::LocationDecoration*>>
+  std::vector<std::pair<const Variable*, ast::LocationDecoration*>>
   ReferencedLocationVariables() const;
 
   /// Retrieves any referenced builtin variables
   /// @returns the <variable, decoration> pair.
-  const std::vector<std::pair<const Variable*, ast::BuiltinDecoration*>>
+  std::vector<std::pair<const Variable*, ast::BuiltinDecoration*>>
   ReferencedBuiltinVariables() const;
 
   /// Retrieves any referenced uniform variables. Note, the variables must be
   /// decorated with both binding and group decorations.
   /// @returns the referenced uniforms
-  const std::vector<std::pair<const Variable*, BindingInfo>>
-  ReferencedUniformVariables() const;
+  VariableBindings ReferencedUniformVariables() const;
 
   /// Retrieves any referenced storagebuffer variables. Note, the variables
   /// must be decorated with both binding and group decorations.
   /// @returns the referenced storagebuffers
-  const std::vector<std::pair<const Variable*, BindingInfo>>
-  ReferencedStorageBufferVariables() const;
+  VariableBindings ReferencedStorageBufferVariables() const;
 
   /// Retrieves any referenced regular Sampler variables. Note, the
   /// variables must be decorated with both binding and group decorations.
   /// @returns the referenced storagebuffers
-  const std::vector<std::pair<const Variable*, BindingInfo>>
-  ReferencedSamplerVariables() const;
+  VariableBindings ReferencedSamplerVariables() const;
 
   /// Retrieves any referenced comparison Sampler variables. Note, the
   /// variables must be decorated with both binding and group decorations.
   /// @returns the referenced storagebuffers
-  const std::vector<std::pair<const Variable*, BindingInfo>>
-  ReferencedComparisonSamplerVariables() const;
+  VariableBindings ReferencedComparisonSamplerVariables() const;
 
   /// Retrieves any referenced sampled textures variables. Note, the
   /// variables must be decorated with both binding and group decorations.
   /// @returns the referenced sampled textures
-  const std::vector<std::pair<const Variable*, BindingInfo>>
-  ReferencedSampledTextureVariables() const;
+  VariableBindings ReferencedSampledTextureVariables() const;
 
   /// Retrieves any referenced multisampled textures variables. Note, the
   /// variables must be decorated with both binding and group decorations.
   /// @returns the referenced sampled textures
-  const std::vector<std::pair<const Variable*, BindingInfo>>
-  ReferencedMultisampledTextureVariables() const;
+  VariableBindings ReferencedMultisampledTextureVariables() const;
 
   /// Retrieves any referenced storage texture variables. Note, the variables
   /// must be decorated with both binding and group decorations.
   /// @returns the referenced storage textures
-  const std::vector<std::pair<const Variable*, BindingInfo>>
-  ReferencedStorageTextureVariables() const;
+  VariableBindings ReferencedStorageTextureVariables() const;
 
   /// Retrieves any locally referenced builtin variables
   /// @returns the <variable, decoration> pairs.
-  const std::vector<std::pair<const Variable*, ast::BuiltinDecoration*>>
+  std::vector<std::pair<const Variable*, ast::BuiltinDecoration*>>
   LocalReferencedBuiltinVariables() const;
 
   /// Checks if the given entry point is an ancestor
@@ -141,10 +137,9 @@ class Function : public Castable<Function, CallTarget> {
   bool HasAncestorEntryPoint(Symbol sym) const;
 
  private:
-  const std::vector<std::pair<const Variable*, BindingInfo>>
-  ReferencedSamplerVariablesImpl(type::SamplerKind kind) const;
-  const std::vector<std::pair<const Variable*, BindingInfo>>
-  ReferencedSampledTextureVariablesImpl(bool multisampled) const;
+  VariableBindings ReferencedSamplerVariablesImpl(type::SamplerKind kind) const;
+  VariableBindings ReferencedSampledTextureVariablesImpl(
+      bool multisampled) const;
 
   ast::Function* const declaration_;
   std::vector<const Variable*> const referenced_module_vars_;

src/semantic/sem_function.cc

@@ -57,7 +57,7 @@ Function::Function(ast::Function* declaration,
 
 Function::~Function() = default;
 
-const std::vector<std::pair<const Variable*, ast::LocationDecoration*>>
+std::vector<std::pair<const Variable*, ast::LocationDecoration*>>
 Function::ReferencedLocationVariables() const {
   std::vector<std::pair<const Variable*, ast::LocationDecoration*>> ret;
 
@@ -72,9 +72,8 @@ Function::ReferencedLocationVariables() const {
   return ret;
 }
 
-const std::vector<std::pair<const Variable*, Function::BindingInfo>>
-Function::ReferencedUniformVariables() const {
-  std::vector<std::pair<const Variable*, Function::BindingInfo>> ret;
+Function::VariableBindings Function::ReferencedUniformVariables() const {
+  VariableBindings ret;
 
   for (auto* var : ReferencedModuleVariables()) {
     if (var->StorageClass() != ast::StorageClass::kUniform) {
@@ -99,9 +98,8 @@ Function::ReferencedUniformVariables() const {
   return ret;
 }
 
-const std::vector<std::pair<const Variable*, Function::BindingInfo>>
-Function::ReferencedStorageBufferVariables() const {
-  std::vector<std::pair<const Variable*, Function::BindingInfo>> ret;
+Function::VariableBindings Function::ReferencedStorageBufferVariables() const {
+  VariableBindings ret;
 
   for (auto* var : ReferencedModuleVariables()) {
     if (var->StorageClass() != ast::StorageClass::kStorage) {
@@ -126,7 +124,7 @@ Function::ReferencedStorageBufferVariables() const {
   return ret;
 }
 
-const std::vector<std::pair<const Variable*, ast::BuiltinDecoration*>>
+std::vector<std::pair<const Variable*, ast::BuiltinDecoration*>>
 Function::ReferencedBuiltinVariables() const {
   std::vector<std::pair<const Variable*, ast::BuiltinDecoration*>> ret;
 
@@ -141,29 +139,26 @@ Function::ReferencedBuiltinVariables() const {
   return ret;
 }
 
-const std::vector<std::pair<const Variable*, Function::BindingInfo>>
-Function::ReferencedSamplerVariables() const {
+Function::VariableBindings Function::ReferencedSamplerVariables() const {
   return ReferencedSamplerVariablesImpl(type::SamplerKind::kSampler);
 }
 
-const std::vector<std::pair<const Variable*, Function::BindingInfo>>
-Function::ReferencedComparisonSamplerVariables() const {
+Function::VariableBindings Function::ReferencedComparisonSamplerVariables()
+    const {
   return ReferencedSamplerVariablesImpl(type::SamplerKind::kComparisonSampler);
 }
 
-const std::vector<std::pair<const Variable*, Function::BindingInfo>>
-Function::ReferencedSampledTextureVariables() const {
+Function::VariableBindings Function::ReferencedSampledTextureVariables() const {
   return ReferencedSampledTextureVariablesImpl(false);
 }
 
-const std::vector<std::pair<const Variable*, Function::BindingInfo>>
-Function::ReferencedMultisampledTextureVariables() const {
+Function::VariableBindings Function::ReferencedMultisampledTextureVariables()
+    const {
   return ReferencedSampledTextureVariablesImpl(true);
 }
 
-const std::vector<std::pair<const Variable*, Function::BindingInfo>>
-Function::ReferencedStorageTextureVariables() const {
-  std::vector<std::pair<const Variable*, Function::BindingInfo>> ret;
+Function::VariableBindings Function::ReferencedStorageTextureVariables() const {
+  VariableBindings ret;
 
   for (auto* var : ReferencedModuleVariables()) {
     auto* unwrapped_type = var->Declaration()->type()->UnwrapIfNeeded();
@@ -190,7 +185,7 @@ Function::ReferencedStorageTextureVariables() const {
   return ret;
 }
 
-const std::vector<std::pair<const Variable*, ast::BuiltinDecoration*>>
+std::vector<std::pair<const Variable*, ast::BuiltinDecoration*>>
 Function::LocalReferencedBuiltinVariables() const {
   std::vector<std::pair<const Variable*, ast::BuiltinDecoration*>> ret;
 
@@ -214,9 +209,9 @@ bool Function::HasAncestorEntryPoint(Symbol symbol) const {
   return false;
 }
 
-const std::vector<std::pair<const Variable*, Function::BindingInfo>>
-Function::ReferencedSamplerVariablesImpl(type::SamplerKind kind) const {
-  std::vector<std::pair<const Variable*, Function::BindingInfo>> ret;
+Function::VariableBindings Function::ReferencedSamplerVariablesImpl(
+    type::SamplerKind kind) const {
+  VariableBindings ret;
 
   for (auto* var : ReferencedModuleVariables()) {
     auto* unwrapped_type = var->Declaration()->type()->UnwrapIfNeeded();
@@ -244,9 +239,9 @@ Function::ReferencedSamplerVariablesImpl(type::SamplerKind kind) const {
   return ret;
 }
 
-const std::vector<std::pair<const Variable*, Function::BindingInfo>>
-Function::ReferencedSampledTextureVariablesImpl(bool multisampled) const {
-  std::vector<std::pair<const Variable*, Function::BindingInfo>> ret;
+Function::VariableBindings Function::ReferencedSampledTextureVariablesImpl(
+    bool multisampled) const {
+  VariableBindings ret;
 
   for (auto* var : ReferencedModuleVariables()) {
     auto* unwrapped_type = var->Declaration()->type()->UnwrapIfNeeded();