resolver: Allow multiple internal decorations

Sometimes a stack of transforms will generate multiple different
DisableValidationDecorations on a single node.

Change-Id: Id4afa148360f98796e67017a9bbdd8adf12eed58
Reviewed-on: https://dawn-review.googlesource.com/c/tint/+/54700
Auto-Submit: James Price <jrprice@google.com>
Commit-Queue: Ben Clayton <bclayton@google.com>
Kokoro: Kokoro <noreply+kokoro@google.com>
Reviewed-by: Ben Clayton <bclayton@google.com>

src/resolver/decoration_validation_test.cc

@@ -13,6 +13,7 @@
 // limitations under the License.
 
 #include "src/ast/access_decoration.h"
+#include "src/ast/disable_validation_decoration.h"
 #include "src/ast/override_decoration.h"
 #include "src/ast/return_statement.h"
 #include "src/ast/stage_decoration.h"
@@ -377,6 +378,22 @@ TEST_F(VariableDecorationTest, DuplicateDecoration) {
 12:34 note: first decoration declared here)");
 }
 
+TEST_F(VariableDecorationTest, DuplicateInternalDecoration) {
+  auto* s =
+      Param("s", ty.sampler(ast::SamplerKind::kSampler),
+            ast::DecorationList{
+                create<ast::BindingDecoration>(0),
+                create<ast::GroupDecoration>(0),
+                ASTNodes().Create<ast::DisableValidationDecoration>(
+                    ID(), ast::DisabledValidation::kBindingPointCollision),
+                ASTNodes().Create<ast::DisableValidationDecoration>(
+                    ID(), ast::DisabledValidation::kEntryPointParameter),
+            });
+  Func("f", {s}, ty.void_(), {});
+
+  EXPECT_TRUE(r()->Resolve()) << r()->error();
+}
+
 using ConstantDecorationTest = TestWithParams;
 TEST_P(ConstantDecorationTest, IsValid) {
   auto& params = GetParam();

src/resolver/resolver.cc

@@ -3340,7 +3340,7 @@ bool Resolver::ValidateNoDuplicateDecorations(
   std::unordered_map<const TypeInfo*, Source> seen;
   for (auto* d : decorations) {
     auto res = seen.emplace(&d->TypeInfo(), d->source());
-    if (!res.second) {
+    if (!res.second && !d->Is<ast::InternalDecoration>()) {
       diagnostics_.add_error("duplicate " + d->name() + " decoration",
                              d->source());
       diagnostics_.add_note("first decoration declared here",