Add case type determination

This CL adds type determination for case statements.

Bug: tint:5
Change-Id: I353232bd68a524a09de60fa73256b51d2be51c57
Reviewed-on: https://dawn-review.googlesource.com/c/tint/+/18830
Reviewed-by: David Neto <dneto@google.com>

src/type_determiner.cc

diff --git a/src/type_determiner.cc b/src/type_determiner.cc
index 8eed309..8418998 100644
--- a/src/type_determiner.cc
+++ b/src/type_determiner.cc
@@ -16,6 +16,7 @@
 
 #include "src/ast/assignment_statement.h"
 #include "src/ast/break_statement.h"
+#include "src/ast/case_statement.h"
 #include "src/ast/scalar_constructor_expression.h"
 #include "src/ast/type_constructor_expression.h"
 
@@ -80,6 +81,10 @@
     auto b = stmt->AsBreak();
     return DetermineResultType(b->conditional());
   }
+  if (stmt->IsCase()) {
+    auto c = stmt->AsCase();
+    return DetermineResultType(c->body());
+  }
 
   error_ = "unknown statement type for type determination";
   return false;

src/type_determiner_test.cc

diff --git a/src/type_determiner_test.cc b/src/type_determiner_test.cc
index a4c8087..fb244d0 100644
--- a/src/type_determiner_test.cc
+++ b/src/type_determiner_test.cc
@@ -20,6 +20,7 @@
 #include "gtest/gtest.h"
 #include "src/ast/assignment_statement.h"
 #include "src/ast/break_statement.h"
+#include "src/ast/case_statement.h"
 #include "src/ast/float_literal.h"
 #include "src/ast/int_literal.h"
 #include "src/ast/scalar_constructor_expression.h"
@@ -78,6 +79,32 @@
   EXPECT_TRUE(cond_ptr->result_type()->IsI32());
 }
 
+TEST_F(TypeDeterminerTest, Stmt_Case) {
+  ast::type::I32Type i32;
+  ast::type::F32Type f32;
+
+  auto lhs = std::make_unique<ast::ScalarConstructorExpression>(
+      std::make_unique<ast::IntLiteral>(&i32, 2));
+  auto lhs_ptr = lhs.get();
+
+  auto rhs = std::make_unique<ast::ScalarConstructorExpression>(
+      std::make_unique<ast::FloatLiteral>(&f32, 2.3f));
+  auto rhs_ptr = rhs.get();
+
+  ast::StatementList body;
+  body.push_back(std::make_unique<ast::AssignmentStatement>(std::move(lhs),
+                                                            std::move(rhs)));
+
+  ast::CaseStatement cse(std::make_unique<ast::IntLiteral>(&i32, 3),
+                         std::move(body));
+
+  EXPECT_TRUE(td()->DetermineResultType(&cse));
+  ASSERT_NE(lhs_ptr->result_type(), nullptr);
+  ASSERT_NE(rhs_ptr->result_type(), nullptr);
+  EXPECT_TRUE(lhs_ptr->result_type()->IsI32());
+  EXPECT_TRUE(rhs_ptr->result_type()->IsF32());
+}
+
 TEST_F(TypeDeterminerTest, Expr_Constructor_Scalar) {
   ast::type::F32Type f32;
   ast::ScalarConstructorExpression s(