Make local.tee's type its local's type (#2511)

According to the current spec, `local.tee`'s return type should be the
same as its local's type. (Discussions on whether we should change this
rule is going on in WebAssembly/reference-types#55, but here I will
assume this spec does not change. If this changes, we should change many
parts of Binaryen transformation anyway...)

But currently in Binaryen `local.tee`'s type is computed from its
value's type. This didn't make any difference in the MVP, but after we
have subtype relationship in #2451, this can become a problem. For
example:
```
(func $test (result funcref) (local $0 anyref)
  (local.tee $0
    (ref.func $test)
  )
)
```
This shouldn't validate in the spec, but this will pass Binaryen
validation with the current `local.tee` implementation.

This makes `local.tee`'s type computed from the local's type, and makes
`LocalSet::makeTee` get a type parameter, to which we should pass the
its corresponding local's type. We don't embed the local type in the
class `LocalSet` because it may increase memory size.

This also fixes the type of `local.get` to be the local type where
`local.get` and `local.set` pair is created from `local.tee`.

2 files changed, 2 insertions, 2 deletions

diff --git a/src/ir/ExpressionManipulator.cpp b/src/ir/ExpressionManipulator.cpp
index fd0e6fd75..fbee9f9c1 100644
--- a/src/ir/ExpressionManipulator.cpp
+++ b/src/ir/ExpressionManipulator.cpp
@@ -91,7 +91,7 @@ flexibleCopy(Expression* original, Module& wasm, CustomCopier custom) {
     }
     Expression* visitLocalSet(LocalSet* curr) {
       if (curr->isTee()) {
-        return builder.makeLocalTee(curr->index, copy(curr->value));
+        return builder.makeLocalTee(curr->index, copy(curr->value), curr->type);
       } else {
         return builder.makeLocalSet(curr->index, copy(curr->value));
       }
diff --git a/src/ir/localize.h b/src/ir/localize.h
index ff454382d..733e7bdec 100644
--- a/src/ir/localize.h
+++ b/src/ir/localize.h
@@ -36,7 +36,7 @@ struct Localizer {
       index = set->index;
     } else {
       index = Builder::addVar(func, expr->type);
-      expr = Builder(*wasm).makeLocalTee(index, expr);
+      expr = Builder(*wasm).makeLocalTee(index, expr, expr->type);
     }
   }
 };