[spirv-writer] Split the constructor expression method.

This CL splits the TypeConstructor code out of the generic
ConstructorExpression to make the code separation clearer.

Bug: tint:5
Change-Id: I441955c3b09a30b2d02f542f4b7c8e80ff8d9d86
Reviewed-on: https://dawn-review.googlesource.com/c/tint/+/20640
Reviewed-by: Ryan Harrison <rharrison@chromium.org>

src/reader/spirv/function.cc

@@ -879,7 +879,8 @@ bool FunctionEmitter::FindSwitchCaseHeaders() {
     for (uint32_t case_target_id : case_targets) {
       auto* case_block = GetBlockInfo(case_target_id);
 
-      case_block->case_values = std::make_unique<std::vector<uint64_t>>(std::move(block_to_values[case_target_id]));
+      case_block->case_values = std::make_unique<std::vector<uint64_t>>(
+          std::move(block_to_values[case_target_id]));
 
       // A case target can't be a back-edge.
       if (construct->begin_pos >= case_block->pos) {

src/writer/spirv/builder.cc

@@ -661,7 +661,17 @@ uint32_t Builder::GenerateConstructorExpression(
     return GenerateLiteralIfNeeded(expr->AsScalarConstructor()->literal());
   }
   if (expr->IsTypeConstructor()) {
-    auto* init = expr->AsTypeConstructor();
+    return GenerateTypeConstructorExpression(expr->AsTypeConstructor(),
+                                             is_global_init);
+  }
+
+  error_ = "unknown constructor expression";
+  return 0;
+}
+
+uint32_t Builder::GenerateTypeConstructorExpression(
+    ast::TypeConstructorExpression* init,
+    bool is_global_init) {
   auto type_id = GenerateTypeIfNeeded(init->type());
   if (type_id == 0) {
     return 0;
@@ -742,10 +752,6 @@ uint32_t Builder::GenerateConstructorExpression(
   return result.to_i();
 }
 
-  error_ = "unknown constructor expression";
-  return 0;
-}
-
 uint32_t Builder::GenerateLiteralIfNeeded(ast::Literal* lit) {
   auto type_id = GenerateTypeIfNeeded(lit->type());
   if (type_id == 0) {

src/writer/spirv/builder.h

@@ -26,6 +26,7 @@
 #include "src/ast/literal.h"
 #include "src/ast/module.h"
 #include "src/ast/struct_member.h"
+#include "src/ast/type_constructor_expression.h"
 #include "src/scope_stack.h"
 #include "src/writer/spirv/function.h"
 #include "src/writer/spirv/instruction.h"
@@ -200,12 +201,19 @@ class Builder {
   /// Generates an import instruction
   /// @param imp the import
   void GenerateImport(ast::Import* imp);
-  /// Generates an constructor expression
+  /// Generates a constructor expression
   /// @param expr the expression to generate
   /// @param is_global_init set true if this is a global variable constructor
   /// @returns the ID of the expression or 0 on failure.
   uint32_t GenerateConstructorExpression(ast::ConstructorExpression* expr,
                                          bool is_global_init);
+  /// Generates a type constructor expression
+  /// @param init the expression to generate
+  /// @param is_global_init set true if this is a global variable constructor
+  /// @returns the ID of the expression or 0 on failure.
+  uint32_t GenerateTypeConstructorExpression(
+      ast::TypeConstructorExpression* init,
+      bool is_global_init);
   /// Generates a literal constant if needed
   /// @param lit the literal to generate
   /// @returns the ID on success or 0 on failure