Update message when indexing a scalar.

This CL updates the member accessor error message when accessing a
scalar to be easier to understand.

Bug: tint:1201
Change-Id: I40611bf8769eba1f98a6f13ca9a1c11d65d35396
Reviewed-on: https://dawn-review.googlesource.com/c/dawn/+/172641
Kokoro: Kokoro <noreply+kokoro@google.com>
Reviewed-by: Ben Clayton <bclayton@google.com>
Commit-Queue: dan sinclair <dsinclair@chromium.org>

src/tint/lang/wgsl/resolver/array_accessor_test.cc

diff --git a/src/tint/lang/wgsl/resolver/array_accessor_test.cc b/src/tint/lang/wgsl/resolver/array_accessor_test.cc
index 937568d..b3e98ed 100644
--- a/src/tint/lang/wgsl/resolver/array_accessor_test.cc
+++ b/src/tint/lang/wgsl/resolver/array_accessor_test.cc
@@ -27,9 +27,8 @@
 
 #include "src/tint/lang/wgsl/resolver/resolver.h"
 
-#include "gmock/gmock.h"
+#include "gtest/gtest.h"
 #include "src/tint/lang/core/fluent_types.h"
-#include "src/tint/lang/core/type/reference.h"
 #include "src/tint/lang/wgsl/resolver/resolver_helper_test.h"
 #include "src/tint/lang/wgsl/sem/index_accessor_expression.h"
 

src/tint/lang/wgsl/resolver/resolver.cc

diff --git a/src/tint/lang/wgsl/resolver/resolver.cc b/src/tint/lang/wgsl/resolver/resolver.cc
index 4595afa..76b9ff9 100644
--- a/src/tint/lang/wgsl/resolver/resolver.cc
+++ b/src/tint/lang/wgsl/resolver/resolver.cc
@@ -3584,9 +3584,8 @@
         },
 
         [&](Default) {
-            AddError("invalid member accessor expression. Expected vector or struct, got '" +
-                         sem_.TypeNameOf(storage_ty) + "'",
-                     expr->member->source);
+            AddError("cannot index into expression of type '" + sem_.TypeNameOf(storage_ty) + "'",
+                     expr->object->source);
             return nullptr;
         });
 }

src/tint/lang/wgsl/resolver/resolver_test.cc

diff --git a/src/tint/lang/wgsl/resolver/resolver_test.cc b/src/tint/lang/wgsl/resolver/resolver_test.cc
index fe4027e..ad94a6f 100644
--- a/src/tint/lang/wgsl/resolver/resolver_test.cc
+++ b/src/tint/lang/wgsl/resolver/resolver_test.cc
@@ -1242,6 +1242,15 @@
 12:34 note: are you missing '()'?)");
 }
 
+TEST_F(ResolverTest, Expr_MemberAccessor_NonCompoundType) {
+    GlobalConst("depth", ty.i32(), Expr(3_i));
+    auto* mem = MemberAccessor(Ident(Source{{12, 34}}, "depth"), "x");
+    WrapInFunction(mem);
+
+    EXPECT_FALSE(r()->Resolve()) << r()->error();
+    EXPECT_EQ(r()->error(), R"(12:34 error: cannot index into expression of type 'i32')");
+}
+
 TEST_F(ResolverTest, Expr_MemberAccessor_Struct) {
     auto* st =
         Structure("S", Vector{Member("first_member", ty.i32()), Member("second_member", ty.f32())});