Allow Box containing shared type from other module

#541, but for Box in addition to Vec.

Author: dtolnay

syntax/check.rs

@@ -76,6 +76,7 @@ fn check_type_ident(cx: &mut Check, ident: &Ident) {
 fn check_type_box(cx: &mut Check, ptr: &Ty1) {
     if let Type::Ident(ident) = &ptr.inner {
         if cx.types.cxx.contains(&ident.rust)
+            && !cx.types.aliases.contains_key(&ident.rust)
             && !cx.types.structs.contains_key(&ident.rust)
             && !cx.types.enums.contains_key(&ident.rust)
         {
@@ -329,6 +330,7 @@ fn check_api_type(cx: &mut Check, ety: &ExternType) {
             TrivialReason::StructField(strct) => format!("a field of `{}`", strct.name.rust),
             TrivialReason::FunctionArgument(efn) => format!("an argument of `{}`", efn.name.rust),
             TrivialReason::FunctionReturn(efn) => format!("a return value of `{}`", efn.name.rust),
+            TrivialReason::BoxTarget => format!("Box<{}>", ety.name.rust),
             TrivialReason::VecElement => format!("a vector element in Vec<{}>", ety.name.rust),
         };
         let msg = format!(

syntax/types.rs

@@ -202,9 +202,16 @@ impl<'a> Types<'a> {
             }
         }
         for ty in &all {
-            if let Type::RustVec(ty) = ty {
-                let reason = TrivialReason::VecElement;
-                insist_alias_types_are_trivial(&ty.inner, reason);
+            match ty {
+                Type::RustBox(ty) => {
+                    let reason = TrivialReason::BoxTarget;
+                    insist_alias_types_are_trivial(&ty.inner, reason);
+                }
+                Type::RustVec(ty) => {
+                    let reason = TrivialReason::VecElement;
+                    insist_alias_types_are_trivial(&ty.inner, reason);
+                }
+                _ => {}
             }
         }
 
@@ -303,6 +310,7 @@ pub enum TrivialReason<'a> {
     StructField(&'a Struct),
     FunctionArgument(&'a ExternFn),
     FunctionReturn(&'a ExternFn),
+    BoxTarget,
     VecElement,
 }