Change the elems parameter of declare_table_elements to a boxed slice.

Implementations that want a full `Vec` can use `into_vec` to convert it
back.

lib/wasm/src/environ/dummy.rs

@@ -402,7 +402,7 @@ impl<'data> ModuleEnvironment<'data> for DummyEnvironment {
         _table_index: TableIndex,
         _base: Option<GlobalIndex>,
         _offset: usize,
-        _elements: Vec<FuncIndex>,
+        _elements: Box<[FuncIndex]>,
     ) {
         // We do nothing
     }

lib/wasm/src/environ/spec.rs

@@ -14,8 +14,8 @@ use cranelift_codegen::ir::immediates::Offset32;
 use cranelift_codegen::ir::{self, InstBuilder};
 use cranelift_codegen::isa::TargetFrontendConfig;
 use failure_derive::Fail;
+use std::boxed::Box;
 use std::convert::From;
-use std::vec::Vec;
 use wasmparser::BinaryReaderError;
 
 /// The value of a WebAssembly global variable.
@@ -336,7 +336,7 @@ pub trait ModuleEnvironment<'data> {
         table_index: TableIndex,
         base: Option<GlobalIndex>,
         offset: usize,
-        elements: Vec<FuncIndex>,
+        elements: Box<[FuncIndex]>,
     );
 
     /// Provides the contents of a function body.

lib/wasm/src/sections_translator.rs

@@ -253,7 +253,12 @@ pub fn parse_element_section<'data>(
             let x = item?;
             elems.push(FuncIndex::from_u32(x));
         }
-        environ.declare_table_elements(TableIndex::from_u32(table_index), base, offset, elems)
+        environ.declare_table_elements(
+            TableIndex::from_u32(table_index),
+            base,
+            offset,
+            elems.into_boxed_slice(),
+        )
     }
     Ok(())
 }