Merge #120: proxy-types.h: add static_assert to detect int/enum size mismatch

110349f test: Add coverage for enum/int conversions (Ryan Ofsky)
bbc80ab proxy-types.h: add static_assert to detect when an int fields is too small to hold an enum value (Ryan Ofsky)

Pull request description:

  Add static_assert to detect when an int field is too small to hold an enum value

  This catches the bug TheCharlatan pointed out in bitcoin/bitcoin#29409 (comment)

Top commit has no ACKs.

Tree-SHA512: cc0adc905e6a6fbd89dd970e5b6675279a514c4e47579b2ef6617c76f0cb18a50dc56539dac300dd89939d5b65cae2e1967c5fae2926b25fe0d36609e86ecb86

Author: ryanofsky

include/mp/proxy-types.h

@@ -963,6 +963,9 @@ LocalType BuildPrimitive(InvokeContext& invoke_context,
     TypeList<LocalType>,
     typename std::enable_if<std::is_enum<Value>::value>::type* enable = nullptr)
 {
+    using E = std::make_unsigned_t<std::underlying_type_t<Value>>;
+    using T = std::make_unsigned_t<LocalType>;
+    static_assert(std::numeric_limits<T>::max() >= std::numeric_limits<E>::max(), "mismatched integral/enum types");
     return static_cast<LocalType>(value);
 }
 

test/mp/test/foo.capnp

@@ -27,6 +27,7 @@ interface FooInterface $Proxy.wrap("mp::test::FooImplementation") {
     passEmpty @12 (arg :FooEmpty) -> (result :FooEmpty);
     passMessage @13 (arg :FooMessage) -> (result :FooMessage);
     passMutable @14 (arg :FooMutable) -> (arg :FooMutable);
+    passEnum @15 (arg :Int32) -> (result :Int32);
 }
 
 interface FooCallback $Proxy.wrap("mp::test::FooCallback") {

test/mp/test/foo.h

@@ -21,6 +21,8 @@ struct FooStruct
     std::vector<bool> vbool;
 };
 
+enum class FooEnum : int { ONE = 1, TWO = 2, };
+
 struct FooCustom
 {
     std::string v1;
@@ -72,6 +74,7 @@ class FooImplementation
     FooEmpty passEmpty(FooEmpty foo) { return foo; }
     FooMessage passMessage(FooMessage foo) { foo.message += " call"; return foo; }
     void passMutable(FooMutable& foo) { foo.message += " call"; }
+    FooEnum passEnum(FooEnum foo) { return foo; }
     std::shared_ptr<FooCallback> m_callback;
 };