From 9609ebf3a9bd8919dd0228970f31e284da190776 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Simon=20Z=C3=BCnd?= <szuend@chromium.org>
Date: Fri, 24 May 2019 13:29:51 +0200
Subject: [PATCH] [torque] Fix crash when declaring a variable without type
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This CL fixes a crash when "constexpr" is infered from the intializer
expression of a variable declaration.

R=sigurds@chromium.org

Bug: v8:7793
Change-Id: I0ec51280fa145d874424e885905bbf79c93b3904
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/1627983
Commit-Queue: Simon Zünd <szuend@chromium.org>
Auto-Submit: Simon Zünd <szuend@chromium.org>
Reviewed-by: Sigurd Schneider <sigurds@chromium.org>
Cr-Commit-Position: refs/heads/master@{#61826}
---
 src/torque/implementation-visitor.cc     | 11 +++++++----
 test/unittests/torque/torque-unittest.cc |  6 ++++++
 2 files changed, 13 insertions(+), 4 deletions(-)

diff --git a/src/torque/implementation-visitor.cc b/src/torque/implementation-visitor.cc
index 8b139ade7c..58caa9e1fd 100644
--- a/src/torque/implementation-visitor.cc
+++ b/src/torque/implementation-visitor.cc
@@ -541,10 +541,6 @@ const Type* ImplementationVisitor::Visit(
   base::Optional<const Type*> type;
   if (stmt->type) {
     type = TypeVisitor::ComputeType(*stmt->type);
-    if ((*type)->IsConstexpr() && !stmt->const_qualified) {
-      ReportError(
-          "cannot declare variable with constexpr type. Use 'const' instead.");
-    }
   }
   base::Optional<VisitResult> init_result;
   if (stmt->initializer) {
@@ -553,6 +549,13 @@ const Type* ImplementationVisitor::Visit(
     if (type) {
       init_result = GenerateImplicitConvert(*type, *init_result);
     }
+    type = init_result->type();
+    if ((*type)->IsConstexpr() && !stmt->const_qualified) {
+      Error("Use 'const' instead of 'let' for variable '", stmt->name->value,
+            "' of constexpr type '", (*type)->ToString(), "'.")
+          .Position(stmt->name->pos)
+          .Throw();
+    }
     init_result = scope.Yield(*init_result);
   } else {
     DCHECK(type.has_value());
diff --git a/test/unittests/torque/torque-unittest.cc b/test/unittests/torque/torque-unittest.cc
index 8ad277ec92..9a82498ee4 100644
--- a/test/unittests/torque/torque-unittest.cc
+++ b/test/unittests/torque/torque-unittest.cc
@@ -207,6 +207,12 @@ TEST(Torque, ConditionalFields) {
                            HasSubstr("aligned"));
 }
 
+TEST(Torque, ConstexprLetBindingDoesNotCrash) {
+  ExpectFailingCompilation(
+      R"(macro FooBar() { let foo = 0; check(foo >= 0); })",
+      HasSubstr("Use 'const' instead of 'let' for variable 'foo'"));
+}
+
 }  // namespace torque
 }  // namespace internal
 }  // namespace v8