diff --git a/src/tint/resolver/array_accessor_test.cc b/src/tint/resolver/array_accessor_test.cc
new file mode 100644
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+++ b/src/tint/resolver/array_accessor_test.cc
@@ -0,0 +1,312 @@
+// Copyright 2021 The Tint Authors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#include "src/tint/resolver/resolver.h"
+
+#include "gmock/gmock.h"
+#include "src/tint/resolver/resolver_test_helper.h"
+#include "src/tint/sem/reference_type.h"
+
+namespace tint {
+namespace resolver {
+namespace {
+
+using ResolverIndexAccessorTest = ResolverTest;
+
+TEST_F(ResolverIndexAccessorTest, Matrix_Dynamic_F32) {
+  Global("my_var", ty.mat2x3<f32>(), ast::StorageClass::kPrivate);
+  auto* acc = IndexAccessor("my_var", Expr(Source{{12, 34}}, 1.0f));
+  WrapInFunction(acc);
+
+  EXPECT_FALSE(r()->Resolve());
+  EXPECT_EQ(r()->error(),
+            "12:34 error: index must be of type 'i32' or 'u32', found: 'f32'");
+}
+
+TEST_F(ResolverIndexAccessorTest, Matrix_Dynamic_Ref) {
+  Global("my_var", ty.mat2x3<f32>(), ast::StorageClass::kPrivate);
+  auto* idx = Var("idx", ty.i32(), Construct(ty.i32()));
+  auto* acc = IndexAccessor("my_var", idx);
+  WrapInFunction(Decl(idx), acc);
+
+  EXPECT_TRUE(r()->Resolve()) << r()->error();
+}
+
+TEST_F(ResolverIndexAccessorTest, Matrix_BothDimensions_Dynamic_Ref) {
+  Global("my_var", ty.mat4x4<f32>(), ast::StorageClass::kPrivate);
+  auto* idx = Var("idx", ty.u32(), Expr(3u));
+  auto* idy = Var("idy", ty.u32(), Expr(2u));
+  auto* acc = IndexAccessor(IndexAccessor("my_var", idx), idy);
+  WrapInFunction(Decl(idx), Decl(idy), acc);
+
+  EXPECT_TRUE(r()->Resolve()) << r()->error();
+}
+
+TEST_F(ResolverIndexAccessorTest, Matrix_Dynamic) {
+  GlobalConst("my_const", ty.mat2x3<f32>(), Construct(ty.mat2x3<f32>()));
+  auto* idx = Var("idx", ty.i32(), Construct(ty.i32()));
+  auto* acc = IndexAccessor("my_const", Expr(Source{{12, 34}}, idx));
+  WrapInFunction(Decl(idx), acc);
+
+  EXPECT_TRUE(r()->Resolve());
+  EXPECT_EQ(r()->error(), "");
+}
+
+TEST_F(ResolverIndexAccessorTest, Matrix_XDimension_Dynamic) {
+  GlobalConst("my_var", ty.mat4x4<f32>(), Construct(ty.mat4x4<f32>()));
+  auto* idx = Var("idx", ty.u32(), Expr(3u));
+  auto* acc = IndexAccessor("my_var", Expr(Source{{12, 34}}, idx));
+  WrapInFunction(Decl(idx), acc);
+
+  EXPECT_TRUE(r()->Resolve());
+  EXPECT_EQ(r()->error(), "");
+}
+
+TEST_F(ResolverIndexAccessorTest, Matrix_BothDimension_Dynamic) {
+  GlobalConst("my_var", ty.mat4x4<f32>(), Construct(ty.mat4x4<f32>()));
+  auto* idx = Var("idy", ty.u32(), Expr(2u));
+  auto* acc =
+      IndexAccessor(IndexAccessor("my_var", Expr(Source{{12, 34}}, idx)), 1);
+  WrapInFunction(Decl(idx), acc);
+
+  EXPECT_TRUE(r()->Resolve());
+  EXPECT_EQ(r()->error(), "");
+}
+
+TEST_F(ResolverIndexAccessorTest, Matrix) {
+  Global("my_var", ty.mat2x3<f32>(), ast::StorageClass::kPrivate);
+
+  auto* acc = IndexAccessor("my_var", 2);
+  WrapInFunction(acc);
+
+  EXPECT_TRUE(r()->Resolve()) << r()->error();
+
+  ASSERT_NE(TypeOf(acc), nullptr);
+  ASSERT_TRUE(TypeOf(acc)->Is<sem::Reference>());
+
+  auto* ref = TypeOf(acc)->As<sem::Reference>();
+  ASSERT_TRUE(ref->StoreType()->Is<sem::Vector>());
+  EXPECT_EQ(ref->StoreType()->As<sem::Vector>()->Width(), 3u);
+}
+
+TEST_F(ResolverIndexAccessorTest, Matrix_BothDimensions) {
+  Global("my_var", ty.mat2x3<f32>(), ast::StorageClass::kPrivate);
+
+  auto* acc = IndexAccessor(IndexAccessor("my_var", 2), 1);
+  WrapInFunction(acc);
+
+  EXPECT_TRUE(r()->Resolve()) << r()->error();
+
+  ASSERT_NE(TypeOf(acc), nullptr);
+  ASSERT_TRUE(TypeOf(acc)->Is<sem::Reference>());
+
+  auto* ref = TypeOf(acc)->As<sem::Reference>();
+  EXPECT_TRUE(ref->StoreType()->Is<sem::F32>());
+}
+
+TEST_F(ResolverIndexAccessorTest, Vector_F32) {
+  Global("my_var", ty.vec3<f32>(), ast::StorageClass::kPrivate);
+  auto* acc = IndexAccessor("my_var", Expr(Source{{12, 34}}, 2.0f));
+  WrapInFunction(acc);
+
+  EXPECT_FALSE(r()->Resolve());
+  EXPECT_EQ(r()->error(),
+            "12:34 error: index must be of type 'i32' or 'u32', found: 'f32'");
+}
+
+TEST_F(ResolverIndexAccessorTest, Vector_Dynamic_Ref) {
+  Global("my_var", ty.vec3<f32>(), ast::StorageClass::kPrivate);
+  auto* idx = Var("idx", ty.i32(), Expr(2));
+  auto* acc = IndexAccessor("my_var", idx);
+  WrapInFunction(Decl(idx), acc);
+
+  EXPECT_TRUE(r()->Resolve());
+}
+
+TEST_F(ResolverIndexAccessorTest, Vector_Dynamic) {
+  GlobalConst("my_var", ty.vec3<f32>(), Construct(ty.vec3<f32>()));
+  auto* idx = Var("idx", ty.i32(), Expr(2));
+  auto* acc = IndexAccessor("my_var", Expr(Source{{12, 34}}, idx));
+  WrapInFunction(Decl(idx), acc);
+
+  EXPECT_TRUE(r()->Resolve());
+}
+
+TEST_F(ResolverIndexAccessorTest, Vector) {
+  Global("my_var", ty.vec3<f32>(), ast::StorageClass::kPrivate);
+
+  auto* acc = IndexAccessor("my_var", 2);
+  WrapInFunction(acc);
+
+  EXPECT_TRUE(r()->Resolve()) << r()->error();
+
+  ASSERT_NE(TypeOf(acc), nullptr);
+  ASSERT_TRUE(TypeOf(acc)->Is<sem::Reference>());
+
+  auto* ref = TypeOf(acc)->As<sem::Reference>();
+  EXPECT_TRUE(ref->StoreType()->Is<sem::F32>());
+}
+
+TEST_F(ResolverIndexAccessorTest, Array) {
+  auto* idx = Expr(2);
+  Global("my_var", ty.array<f32, 3>(), ast::StorageClass::kPrivate);
+
+  auto* acc = IndexAccessor("my_var", idx);
+  WrapInFunction(acc);
+
+  EXPECT_TRUE(r()->Resolve()) << r()->error();
+
+  ASSERT_NE(TypeOf(acc), nullptr);
+  ASSERT_TRUE(TypeOf(acc)->Is<sem::Reference>());
+
+  auto* ref = TypeOf(acc)->As<sem::Reference>();
+  EXPECT_TRUE(ref->StoreType()->Is<sem::F32>());
+}
+
+TEST_F(ResolverIndexAccessorTest, Alias_Array) {
+  auto* aary = Alias("myarrty", ty.array<f32, 3>());
+
+  Global("my_var", ty.Of(aary), ast::StorageClass::kPrivate);
+
+  auto* acc = IndexAccessor("my_var", 2);
+  WrapInFunction(acc);
+
+  EXPECT_TRUE(r()->Resolve()) << r()->error();
+
+  ASSERT_NE(TypeOf(acc), nullptr);
+  ASSERT_TRUE(TypeOf(acc)->Is<sem::Reference>());
+
+  auto* ref = TypeOf(acc)->As<sem::Reference>();
+  EXPECT_TRUE(ref->StoreType()->Is<sem::F32>());
+}
+
+TEST_F(ResolverIndexAccessorTest, Array_Constant) {
+  GlobalConst("my_var", ty.array<f32, 3>(), array<f32, 3>());
+
+  auto* acc = IndexAccessor("my_var", 2);
+  WrapInFunction(acc);
+
+  EXPECT_TRUE(r()->Resolve()) << r()->error();
+
+  ASSERT_NE(TypeOf(acc), nullptr);
+  EXPECT_TRUE(TypeOf(acc)->Is<sem::F32>()) << TypeOf(acc)->type_name();
+}
+
+TEST_F(ResolverIndexAccessorTest, Array_Dynamic_I32) {
+  // let a : array<f32, 3> = 0;
+  // var idx : i32 = 0;
+  // var f : f32 = a[idx];
+  auto* a = Const("a", ty.array<f32, 3>(), array<f32, 3>());
+  auto* idx = Var("idx", ty.i32(), Construct(ty.i32()));
+  auto* f = Var("f", ty.f32(), IndexAccessor("a", Expr(Source{{12, 34}}, idx)));
+  Func("my_func", ast::VariableList{}, ty.void_(),
+       {
+           Decl(a),
+           Decl(idx),
+           Decl(f),
+       },
+       ast::AttributeList{});
+
+  EXPECT_TRUE(r()->Resolve());
+  EXPECT_EQ(r()->error(), "");
+}
+
+TEST_F(ResolverIndexAccessorTest, Array_Literal_F32) {
+  // let a : array<f32, 3>;
+  // var f : f32 = a[2.0f];
+  auto* a = Const("a", ty.array<f32, 3>(), array<f32, 3>());
+  auto* f =
+      Var("a_2", ty.f32(), IndexAccessor("a", Expr(Source{{12, 34}}, 2.0f)));
+  Func("my_func", ast::VariableList{}, ty.void_(),
+       {
+           Decl(a),
+           Decl(f),
+       },
+       ast::AttributeList{});
+  EXPECT_FALSE(r()->Resolve());
+  EXPECT_EQ(r()->error(),
+            "12:34 error: index must be of type 'i32' or 'u32', found: 'f32'");
+}
+
+TEST_F(ResolverIndexAccessorTest, Array_Literal_I32) {
+  // let a : array<f32, 3>;
+  // var f : f32 = a[2];
+  auto* a = Const("a", ty.array<f32, 3>(), array<f32, 3>());
+  auto* f = Var("a_2", ty.f32(), IndexAccessor("a", 2));
+  Func("my_func", ast::VariableList{}, ty.void_(),
+       {
+           Decl(a),
+           Decl(f),
+       },
+       ast::AttributeList{});
+  EXPECT_TRUE(r()->Resolve()) << r()->error();
+}
+
+TEST_F(ResolverIndexAccessorTest, EXpr_Deref_FuncGoodParent) {
+  // fn func(p: ptr<function, vec4<f32>>) -> f32 {
+  //     let idx: u32 = u32();
+  //     let x: f32 = (*p)[idx];
+  //     return x;
+  // }
+  auto* p =
+      Param("p", ty.pointer(ty.vec4<f32>(), ast::StorageClass::kFunction));
+  auto* idx = Const("idx", ty.u32(), Construct(ty.u32()));
+  auto* star_p = Deref(p);
+  auto* accessor_expr = IndexAccessor(Source{{12, 34}}, star_p, idx);
+  auto* x = Var("x", ty.f32(), accessor_expr);
+  Func("func", {p}, ty.f32(), {Decl(idx), Decl(x), Return(x)});
+
+  EXPECT_TRUE(r()->Resolve()) << r()->error();
+}
+
+TEST_F(ResolverIndexAccessorTest, EXpr_Deref_FuncBadParent) {
+  // fn func(p: ptr<function, vec4<f32>>) -> f32 {
+  //     let idx: u32 = u32();
+  //     let x: f32 = *p[idx];
+  //     return x;
+  // }
+  auto* p =
+      Param("p", ty.pointer(ty.vec4<f32>(), ast::StorageClass::kFunction));
+  auto* idx = Const("idx", ty.u32(), Construct(ty.u32()));
+  auto* accessor_expr = IndexAccessor(Source{{12, 34}}, p, idx);
+  auto* star_p = Deref(accessor_expr);
+  auto* x = Var("x", ty.f32(), star_p);
+  Func("func", {p}, ty.f32(), {Decl(idx), Decl(x), Return(x)});
+
+  EXPECT_FALSE(r()->Resolve());
+  EXPECT_EQ(
+      r()->error(),
+      "12:34 error: cannot index type 'ptr<function, vec4<f32>, read_write>'");
+}
+
+TEST_F(ResolverIndexAccessorTest, Exr_Deref_BadParent) {
+  // var param: vec4<f32>
+  // let x: f32 = *(&param)[0];
+  auto* param = Var("param", ty.vec4<f32>());
+  auto* idx = Var("idx", ty.u32(), Construct(ty.u32()));
+  auto* addressOf_expr = AddressOf(param);
+  auto* accessor_expr = IndexAccessor(Source{{12, 34}}, addressOf_expr, idx);
+  auto* star_p = Deref(accessor_expr);
+  auto* x = Var("x", ty.f32(), star_p);
+  WrapInFunction(param, idx, x);
+
+  EXPECT_FALSE(r()->Resolve());
+  EXPECT_EQ(
+      r()->error(),
+      "12:34 error: cannot index type 'ptr<function, vec4<f32>, read_write>'");
+}
+
+}  // namespace
+}  // namespace resolver
+}  // namespace tint