Add else statement type determination.

This CL adds type determination for else statements.

Bug: tint:5
Change-Id: Ie859edbc08c191da0a04407c5f56b413a48f1791
Reviewed-on: https://dawn-review.googlesource.com/c/tint/+/18832
Reviewed-by: David Neto <dneto@google.com>

src/type_determiner.cc

@@ -18,6 +18,7 @@
 #include "src/ast/break_statement.h"
 #include "src/ast/case_statement.h"
 #include "src/ast/continue_statement.h"
+#include "src/ast/else_statement.h"
 #include "src/ast/scalar_constructor_expression.h"
 #include "src/ast/type_constructor_expression.h"
 
@@ -90,6 +91,11 @@ bool TypeDeterminer::DetermineResultType(ast::Statement* stmt) {
     auto c = stmt->AsContinue();
     return DetermineResultType(c->conditional());
   }
+  if (stmt->IsElse()) {
+    auto e = stmt->AsElse();
+    return DetermineResultType(e->condition()) &&
+           DetermineResultType(e->body());
+  }
 
   error_ = "unknown statement type for type determination";
   return false;

src/type_determiner_test.cc

@@ -22,6 +22,7 @@
 #include "src/ast/break_statement.h"
 #include "src/ast/case_statement.h"
 #include "src/ast/continue_statement.h"
+#include "src/ast/else_statement.h"
 #include "src/ast/float_literal.h"
 #include "src/ast/int_literal.h"
 #include "src/ast/scalar_constructor_expression.h"
@@ -120,6 +121,35 @@ TEST_F(TypeDeterminerTest, Stmt_Continue) {
   EXPECT_TRUE(cond_ptr->result_type()->IsI32());
 }
 
+TEST_F(TypeDeterminerTest, Stmt_Else) {
+  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::ElseStatement stmt(std::make_unique<ast::ScalarConstructorExpression>(
+                              std::make_unique<ast::IntLiteral>(&i32, 3)),
+                          std::move(body));
+
+  EXPECT_TRUE(td()->DetermineResultType(&stmt));
+  ASSERT_NE(stmt.condition()->result_type(), nullptr);
+  ASSERT_NE(lhs_ptr->result_type(), nullptr);
+  ASSERT_NE(rhs_ptr->result_type(), nullptr);
+  EXPECT_TRUE(stmt.condition()->result_type()->IsI32());
+  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(