Make List constructor give better error messages for non-int arguments

runtime/vm/code_generator.cc

Index: runtime/vm/code_generator.cc
diff --git a/runtime/vm/code_generator.cc b/runtime/vm/code_generator.cc
index 1cd7f5038306d03bdb1d86f0c86d0216fc5c6182..ee84961aff4f4b08291ebacc6ce309a40cc83d52 100644
--- a/runtime/vm/code_generator.cc
+++ b/runtime/vm/code_generator.cc
@@ -106,31 +106,38 @@ DEFINE_RUNTIME_ENTRY(TraceFunctionExit, 1) {
 // Return value: newly allocated array of length arg0.
 DEFINE_RUNTIME_ENTRY(AllocateArray, 2) {
   const Instance& length = Instance::CheckedHandle(arguments.ArgAt(0));
-  if (!length.IsSmi()) {
-    const String& error = String::Handle(String::NewFormatted(
-        "Length must be an integer in the range [0..%" Pd "].",
-        Array::kMaxElements));
-    Exceptions::ThrowArgumentError(error);
-  }
-  const intptr_t len = Smi::Cast(length).Value();
-  if ((len < 0) || (len > Array::kMaxElements)) {
-    const String& error = String::Handle(String::NewFormatted(
-        "Length (%" Pd ") must be an integer in the range [0..%" Pd "].",
-        len, Array::kMaxElements));
-    Exceptions::ThrowArgumentError(error);
-  }
-
-  Heap::Space space = isolate->heap()->SpaceForAllocation(kArrayCid);
-  const Array& array = Array::Handle(Array::New(len, space));
-  arguments.SetReturn(array);
-  TypeArguments& element_type =
-      TypeArguments::CheckedHandle(arguments.ArgAt(1));
-  // An Array is raw or takes one type argument. However, its type argument
-  // vector may be longer than 1 due to a type optimization reusing the type
-  // argument vector of the instantiator.
-  ASSERT(element_type.IsNull() ||
-         ((element_type.Length() >= 1) && element_type.IsInstantiated()));
-  array.SetTypeArguments(element_type);  // May be null.
+  if (!length.IsInteger()) {
+    // Throw: new ArgumentError.value(length, "length", "is not an integer");
+    const Array& args = Array::Handle(Array::New(3));
+    args.SetAt(0, length);
+    args.SetAt(1, Symbols::Length());
+    args.SetAt(2, String::Handle(String::New("is not an integer")));
+    Exceptions::ThrowByType(Exceptions::kArgumentValue, args);
+  }
+  if (length.IsSmi()) {
+    const intptr_t len = Smi::Cast(length).Value();
+    if ((len >= 0) && (len <= Array::kMaxElements)) {
+      Heap::Space space = isolate->heap()->SpaceForAllocation(kArrayCid);
+      const Array& array = Array::Handle(Array::New(len, space));
+      arguments.SetReturn(array);
+      TypeArguments& element_type =
+          TypeArguments::CheckedHandle(arguments.ArgAt(1));
+      // An Array is raw or takes one type argument. However, its type argument
+      // vector may be longer than 1 due to a type optimization reusing the type
+      // argument vector of the instantiator.
+      ASSERT(element_type.IsNull() ||
+             ((element_type.Length() >= 1) && element_type.IsInstantiated()));
+      array.SetTypeArguments(element_type);  // May be null.
+      return;
+    }
+  }
+  // Throw: new RangeError.range(length, 0, Array::kMaxElements, "length");
+  const Array& args = Array::Handle(Array::New(4));
+  args.SetAt(0, length);
+  args.SetAt(1, Integer::Handle(Integer::New(0)));
+  args.SetAt(2, Integer::Handle(Integer::New(Array::kMaxElements)));
+  args.SetAt(3, Symbols::Length());
+  Exceptions::ThrowByType(Exceptions::kRangeRange, args);
 }