Update to the new wasmparser and port to the new readers API.

The new wasmparser API provides dedicated reader types for each section
type, which significantly simplifies the code.

This also changes WasmError::from_binary_reader_error into a From
trait so that we don't have to do .map_err(from_binary_reader_error)
throughout the code.

lib/wasm/src/func_translator.rs

@@ -9,7 +9,7 @@ use cranelift_codegen::entity::EntityRef;
 use cranelift_codegen::ir::{self, Ebb, InstBuilder};
 use cranelift_codegen::timing;
 use cranelift_frontend::{FunctionBuilder, FunctionBuilderContext, Variable};
-use environ::{FuncEnvironment, ReturnMode, WasmError, WasmResult};
+use environ::{FuncEnvironment, ReturnMode, WasmResult};
 use state::TranslationState;
 use wasmparser::{self, BinaryReader};
 
@@ -135,16 +135,12 @@ fn parse_local_decls(
     num_params: usize,
 ) -> WasmResult<()> {
     let mut next_local = num_params;
-    let local_count = reader
-        .read_local_count()
-        .map_err(WasmError::from_binary_reader_error)?;
+    let local_count = reader.read_local_count()?;
 
     let mut locals_total = 0;
     for _ in 0..local_count {
         builder.set_srcloc(cur_srcloc(reader));
-        let (count, ty) = reader
-            .read_local_decl(&mut locals_total)
-            .map_err(WasmError::from_binary_reader_error)?;
+        let (count, ty) = reader.read_local_decl(&mut locals_total)?;
         declare_locals(builder, count, ty, &mut next_local);
     }
 
@@ -195,9 +191,7 @@ fn parse_function_body<FE: FuncEnvironment + ?Sized>(
     // Keep going until the final `End` operator which pops the outermost block.
     while !state.control_stack.is_empty() {
         builder.set_srcloc(cur_srcloc(&reader));
-        let op = reader
-            .read_operator()
-            .map_err(WasmError::from_binary_reader_error)?;
+        let op = reader.read_operator()?;
         translate_operator(op, builder, state, environ)?;
     }