tint/reader: Parse arrays with no type / size

Bug: tint:1628
Change-Id: Ieb3c07e7dae6fd1e5acf4dd4819312092e5b5bf5
Reviewed-on: https://dawn-review.googlesource.com/c/dawn/+/97586
Reviewed-by: David Neto <dneto@google.com>
Reviewed-by: Antonio Maiorano <amaiorano@google.com>
Commit-Queue: Ben Clayton <bclayton@google.com>
Kokoro: Kokoro <noreply+kokoro@google.com>

src/tint/reader/wgsl/parser_impl.cc

@@ -1175,33 +1175,40 @@ Expect<const ast::Type*> ParserImpl::expect_type_decl_vector(const Token& t) {
 Expect<const ast::Type*> ParserImpl::expect_type_decl_array(const Token& t) {
     const char* use = "array declaration";
 
+    struct TypeAndSize {
+        const ast::Type* type = nullptr;
         const ast::Expression* size = nullptr;
+    };
 
-    auto subtype = expect_lt_gt_block(use, [&]() -> Expect<const ast::Type*> {
+    if (!peek_is(Token::Type::kLessThan)) {
+        return builder_.ty.array(make_source_range_from(t.source()), nullptr, nullptr);
+    }
+
+    auto type_size = expect_lt_gt_block(use, [&]() -> Expect<TypeAndSize> {
         auto type = expect_type(use);
         if (type.errored) {
             return Failure::kErrored;
         }
 
-        if (match(Token::Type::kComma)) {
+        if (!match(Token::Type::kComma)) {
-            auto expr = primary_expression();
+            return TypeAndSize{type.value, nullptr};
-            if (expr.errored) {
+        }
+
+        auto size = primary_expression();
+        if (size.errored) {
             return Failure::kErrored;
-            } else if (!expr.matched) {
+        } else if (!size.matched) {
             return add_error(peek(), "expected array size expression");
         }
 
-            size = std::move(expr.value);
+        return TypeAndSize{type.value, size.value};
-        }
-
-        return type.value;
     });
 
-    if (subtype.errored) {
+    if (type_size.errored) {
         return Failure::kErrored;
     }
 
-    return builder_.ty.array(make_source_range_from(t.source()), subtype.value, size);
+    return builder_.ty.array(make_source_range_from(t.source()), type_size->type, type_size->size);
 }
 
 Expect<const ast::Type*> ParserImpl::expect_type_decl_matrix(const Token& t) {

src/tint/reader/wgsl/parser_impl_error_msg_test.cc

@@ -603,7 +603,8 @@ let i : vec2<i32> = vec2<i32>(1., 2.;
 }
 
 TEST_F(ParserImplErrorTest, GlobalDeclLetBadConstLiteral) {
-    EXPECT("let i : vec2<i32> = vec2<i32>(!);",
+    EXPECT(
+        "let i : vec2<i32> = vec2<i32>(!);",
         R"(test.wgsl:1:1 warning: use of deprecated language feature: module-scope 'let' has been replaced with 'const'
 let i : vec2<i32> = vec2<i32>(!);
 ^^^
@@ -821,14 +822,6 @@ type meow = f32
 )");
 }
 
-TEST_F(ParserImplErrorTest, GlobalDeclVarArrayMissingLessThan) {
-    EXPECT("var i : array;",
-           R"(test.wgsl:1:14 error: expected '<' for array declaration
-var i : array;
-             ^
-)");
-}
-
 TEST_F(ParserImplErrorTest, GlobalDeclVarArrayMissingGreaterThan) {
     EXPECT("var i : array<u32, 3;",
            R"(test.wgsl:1:21 error: expected '>' for array declaration

src/tint/reader/wgsl/parser_impl_type_decl_test.cc

@@ -501,6 +501,22 @@ TEST_F(ParserImplTest, TypeDecl_Array_Runtime_Vec) {
     EXPECT_EQ(t.value->source.range, (Source::Range{{1u, 1u}, {1u, 17u}}));
 }
 
+TEST_F(ParserImplTest, TypeDecl_Array_InferTypeAndSize) {
+    auto p = parser("array");
+    auto t = p->type_decl();
+    EXPECT_TRUE(t.matched);
+    EXPECT_FALSE(t.errored);
+    ASSERT_NE(t.value, nullptr) << p->error();
+    ASSERT_FALSE(p->has_error());
+    ASSERT_TRUE(t.value->Is<ast::Array>());
+
+    auto* a = t.value->As<ast::Array>();
+    EXPECT_FALSE(a->IsRuntimeArray());
+    EXPECT_EQ(a->type, nullptr);
+    EXPECT_EQ(a->count, nullptr);
+    EXPECT_EQ(t.value->source.range, (Source::Range{{1u, 1u}, {1u, 6u}}));
+}
+
 TEST_F(ParserImplTest, TypeDecl_Array_BadSize) {
     auto p = parser("array<f32, !>");
     auto t = p->type_decl();
@@ -521,16 +537,6 @@ TEST_F(ParserImplTest, TypeDecl_Array_MissingSize) {
     ASSERT_EQ(p->error(), "1:11: expected array size expression");
 }
 
-TEST_F(ParserImplTest, TypeDecl_Array_MissingLessThan) {
-    auto p = parser("array f32>");
-    auto t = p->type_decl();
-    EXPECT_TRUE(t.errored);
-    EXPECT_FALSE(t.matched);
-    ASSERT_EQ(t.value, nullptr);
-    ASSERT_TRUE(p->has_error());
-    ASSERT_EQ(p->error(), "1:7: expected '<' for array declaration");
-}
-
 TEST_F(ParserImplTest, TypeDecl_Array_MissingGreaterThan) {
     auto p = parser("array<f32");
     auto t = p->type_decl();