Emit deprecation warnings for @stage.

This PR enables the deprecation warnings for the @stage builtin.

Bug: tint:1503
Change-Id: I4a560f451a9ad56bc712f6a04c18eba6ae67ab64
Reviewed-on: https://dawn-review.googlesource.com/c/dawn/+/93121
Reviewed-by: Ben Clayton <bclayton@google.com>
Auto-Submit: Dan Sinclair <dsinclair@chromium.org>
Commit-Queue: Dan Sinclair <dsinclair@chromium.org>

docs/tint/origin-trial-changes.md

@@ -1,5 +1,16 @@
 # Tint changes during Origin Trial
 
+## Changes for M105
+
+### Deprecated Features
+
+* The `@stage` attribute has been deprecated. The short forms should be used
+  instead (`@vertex`, `@fragment`, or `@compute`). [tint:1503](crbug.com/tint/1503)
+
+## Changes for M104
+
+* Parsing of `@compute`, `@fragment` and `@vertex` added.
+
 ## Changes for M103
 
 ### New features

src/tint/reader/wgsl/parser_impl.cc

@@ -3251,6 +3251,7 @@ Maybe<const ast::Attribute*> ParserImpl::attribute() {
         });
     }
 
+    // TODO(crbug.com/tint/1503): Remove when deprecation period is over.
     if (t == kStageAttribute) {
         return expect_paren_block("stage attribute", [&]() -> Result {
             auto stage = expect_pipeline_stage();
@@ -3258,26 +3259,22 @@ Maybe<const ast::Attribute*> ParserImpl::attribute() {
                 return Failure::kErrored;
             }
 
-            // TODO(crbug.com/tint/1503): Enable this once all the Dawn and CTS
+            std::string warning = "remove stage and use @";
-            // tests are updated to use the new format so we can avoid spamming
+            switch (stage.value) {
-            // the log files.
+                case ast::PipelineStage::kVertex:
-            if ((false)) {
+                    warning += "vertex";
-                std::string warning = "stage should use @";
+                    break;
-                switch (stage.value) {
+                case ast::PipelineStage::kFragment:
-                    case ast::PipelineStage::kVertex:
+                    warning += "fragment";
-                        warning += "vertex";
+                    break;
-                        break;
+                case ast::PipelineStage::kCompute:
-                    case ast::PipelineStage::kFragment:
+                    warning += "compute";
-                        warning += "fragment";
+                    break;
-                        break;
+                case ast::PipelineStage::kNone:
-                    case ast::PipelineStage::kCompute:
+                    break;
-                        warning += "compute";
-                        break;
-                    case ast::PipelineStage::kNone:
-                        break;
-                }
-                deprecated(t.source(), warning);
             }
+            deprecated(t.source(), warning);
+
             return create<ast::StageAttribute>(t.source(), stage.value);
         });
     }

src/tint/reader/wgsl/parser_impl_error_msg_test.cc

@@ -316,8 +316,13 @@ TEST_F(ParserImplErrorTest, FunctionDeclStageMissingLParen) {
 }
 
 TEST_F(ParserImplErrorTest, FunctionDeclStageMissingRParen) {
-    EXPECT("@stage(vertex fn f() {}",
+    EXPECT(
-           R"(test.wgsl:1:15 error: expected ')' for stage attribute
+        "@stage(vertex fn f() {}",
+        R"(test.wgsl:1:2 warning: use of deprecated language feature: remove stage and use @vertex
+@stage(vertex fn f() {}
+ ^^^^^
+
+test.wgsl:1:15 error: expected ')' for stage attribute
 @stage(vertex fn f() {}
               ^^
 )");

src/tint/reader/wgsl/parser_impl_function_attribute_test.cc

@@ -263,7 +263,8 @@ TEST_F(ParserImplTest, Attribute_Stage_MissingRightParen) {
     EXPECT_TRUE(attr.errored);
     EXPECT_EQ(attr.value, nullptr);
     EXPECT_TRUE(p->has_error());
-    EXPECT_EQ(p->error(), "1:14: expected ')' for stage attribute");
+    EXPECT_EQ(p->error(), R"(1:1: use of deprecated language feature: remove stage and use @compute
+1:14: expected ')' for stage attribute)");
 }
 
 TEST_F(ParserImplTest, Attribute_Compute) {