Address some review comments

crates/wasmparser/src/binary_reader.rs

@@ -293,7 +293,7 @@ impl<'a> BinaryReader<'a> {
         })
     }
 
-    fn read_export_types(&mut self) -> Result<Vec<ExportType<'a>>> {
+    fn read_export_types(&mut self) -> Result<Box<[ExportType<'a>]>> {
         let pos = self.original_position();
         let exports_len = self.read_var_u32()? as usize;
         if exports_len > MAX_WASM_EXPORTS {
@@ -304,13 +304,19 @@ impl<'a> BinaryReader<'a> {
 
     pub(crate) fn read_import(&mut self) -> Result<Import<'a>> {
         let module = self.read_string()?;
+
+        // For the `field`, figure out if we're the experimental encoding of
+        // single-level imports for the module linking proposal (a single-byte
+        // string which is 0xc0, which is invalid utf-8) or if we have a second
+        // level of import.
         let mut clone = self.clone();
         let field = if clone.read_var_u32()? == 1 && clone.read_u8()? == 0xc0 {
             *self = clone;
             None
         } else {
             Some(self.read_string()?)
         };
+
         let ty = self.read_import_desc()?;
         Ok(Import { module, field, ty })
     }

crates/wasmparser/src/primitives.rs

@@ -159,13 +159,13 @@ pub struct FuncType {
 
 #[derive(Debug, Clone)]
 pub struct InstanceType<'a> {
-    pub exports: Vec<ExportType<'a>>,
+    pub exports: Box<[ExportType<'a>]>,
 }
 
 #[derive(Debug, Clone)]
 pub struct ModuleType<'a> {
-    pub imports: Vec<crate::Import<'a>>,
-    pub exports: Vec<ExportType<'a>>,
+    pub imports: Box<[crate::Import<'a>]>,
+    pub exports: Box<[ExportType<'a>]>,
 }
 
 #[derive(Debug, Clone)]

crates/wasmparser/src/validator.rs

@@ -1033,7 +1033,7 @@ impl<'a> ValidatingParser<'a> {
                 if expected.imports.len() != actual.imports.len() {
                     return self.create_error("mismatched number of module imports");
                 }
-                for (expected, actual) in expected.imports.iter().zip(&actual.imports) {
+                for (expected, actual) in expected.imports.iter().zip(actual.imports.iter()) {
                     self.check_imports_match(&expected.ty, &actual.ty)?;
                 }
                 self.check_export_sets_match(&expected.exports, &actual.exports)?;