Move CheckBuffer to helper from CheckType.

Spilt the CheckBuffer helper out of CheckType.

Change-Id: I6121f28ea748a70a3322cd45dacf8c7b88381caf
Reviewed-on: https://dawn-review.googlesource.com/c/dawn/+/320665
Reviewed-by: James Price <jrprice@google.com>
Commit-Queue: dan sinclair <dsinclair@chromium.org>

src/tint/lang/core/ir/structural_validator.cc

diff --git a/src/tint/lang/core/ir/structural_validator.cc b/src/tint/lang/core/ir/structural_validator.cc
index 4d58242..ff00bd5 100644
--- a/src/tint/lang/core/ir/structural_validator.cc
+++ b/src/tint/lang/core/ir/structural_validator.cc
@@ -706,13 +706,7 @@
             [&](const core::type::BindingArray* t) {
                 return CheckBindingArray(t, diag, addrspace);
             },
-            [&](const core::type::Buffer*) {
-                if (!ir_.properties.Contains(Property::kAllowBufferTypes)) {
-                    diag() << "buffer types are not allowed in this context";
-                    return false;
-                }
-                return true;
-            },
+            [&](const core::type::Buffer*) { return CheckBuffer(diag); },
             [](Default) { return true; });
     };
 
@@ -773,6 +767,14 @@
     }
 }
 
+bool Structural::CheckBuffer(std::function<diag::Diagnostic&()>& diag) {
+    if (!ir_.properties.Contains(Property::kAllowBufferTypes)) {
+        diag() << "buffer types are not allowed in this context";
+        return false;
+    }
+    return true;
+}
+
 bool Structural::CheckBindingArray(const core::type::BindingArray* ba,
                                    std::function<diag::Diagnostic&()>& diag,
                                    core::AddressSpace addrspace) {

src/tint/lang/core/ir/structural_validator.h

diff --git a/src/tint/lang/core/ir/structural_validator.h b/src/tint/lang/core/ir/structural_validator.h
index e051458..15e5265 100644
--- a/src/tint/lang/core/ir/structural_validator.h
+++ b/src/tint/lang/core/ir/structural_validator.h
@@ -388,6 +388,10 @@
                            std::function<diag::Diagnostic&()>& diag,
                            core::AddressSpace addrspace);
 
+    /// Checks that buffers are available
+    /// @param diag a function that creates an error diagnostic for the source of the type
+    bool CheckBuffer(std::function<diag::Diagnostic&()>& diag);
+
     /// Checks that 8-bit types are permitted
     /// @param diag a function that creates an error diagnostic for the source of the type
     /// @param parent the parent type for the 8-bit type