From 8198d57ff235ddf57c9ab48f55a39dcb3037977e Mon Sep 17 00:00:00 2001
From: Ben Clayton <bclayton@google.com>
Date: Mon, 19 Apr 2021 14:37:49 +0000
Subject: [PATCH] writer/wgsl: Handle inferred-type variable declarations

Fixes a null-pointer deference crash.

Bug: tint:672
Change-Id: Icfcb1c8754950ea0e074a0b392d0b34748a13827
Reviewed-on: https://dawn-review.googlesource.com/c/tint/+/48225
Commit-Queue: Ben Clayton <bclayton@chromium.org>
Reviewed-by: James Price <jrprice@google.com>
---
 src/writer/wgsl/generator_impl.cc                  | 10 +++++++---
 .../generator_impl_variable_decl_statement_test.cc | 14 ++++++++++++++
 2 files changed, 21 insertions(+), 3 deletions(-)

diff --git a/src/writer/wgsl/generator_impl.cc b/src/writer/wgsl/generator_impl.cc
index 156b266d48..a93a5bf234 100644
--- a/src/writer/wgsl/generator_impl.cc
+++ b/src/writer/wgsl/generator_impl.cc
@@ -598,9 +598,13 @@ bool GeneratorImpl::EmitVariable(ast::Variable* var) {
     }
   }
 
-  out_ << " " << program_->Symbols().NameFor(var->symbol()) << " : ";
-  if (!EmitType(sem->DeclaredType())) {
-    return false;
+  out_ << " " << program_->Symbols().NameFor(var->symbol());
+
+  if (var->declared_type()) {
+    out_ << " : ";
+    if (!EmitType(var->declared_type())) {
+      return false;
+    }
   }
 
   if (var->constructor() != nullptr) {
diff --git a/src/writer/wgsl/generator_impl_variable_decl_statement_test.cc b/src/writer/wgsl/generator_impl_variable_decl_statement_test.cc
index e27397f2bd..27fa34f602 100644
--- a/src/writer/wgsl/generator_impl_variable_decl_statement_test.cc
+++ b/src/writer/wgsl/generator_impl_variable_decl_statement_test.cc
@@ -68,6 +68,20 @@ TEST_F(WgslGeneratorImplTest, Emit_VariableDeclStatement_Private) {
   EXPECT_EQ(gen.result(), "  var<private> a : f32;\n");
 }
 
+TEST_F(WgslGeneratorImplTest, Emit_VariableDeclStatement_InferredType) {
+  auto* var = Var("a", nullptr, ast::StorageClass::kFunction, Expr(123));
+
+  auto* stmt = create<ast::VariableDeclStatement>(var);
+  WrapInFunction(stmt);
+
+  GeneratorImpl& gen = Build();
+
+  gen.increment_indent();
+
+  ASSERT_TRUE(gen.EmitStatement(stmt)) << gen.error();
+  EXPECT_EQ(gen.result(), "  var a = 123;\n");
+}
+
 }  // namespace
 }  // namespace wgsl
 }  // namespace writer