remove redundant imports and prefer it.first() to it.get(0)

Author: rhysd

spec-test/src/parser.rs

@@ -634,7 +634,7 @@ impl<'s> Parse<'s> for Script<'s> {
         while !parser.is_done()? {
             commands.push(parser.parse()?);
         }
-        let start = commands.get(0).map(Command::start_pos).unwrap_or(0);
+        let start = commands.first().map(Command::start_pos).unwrap_or(0);
         Ok(Script { start, commands })
     }
 }

wain-exec/src/memory.rs

@@ -22,7 +22,7 @@ impl Memory {
     pub fn allocate(memories: &[ast::Memory]) -> Result<Self> {
         // Note: Only one memory exists thanks to validation
         assert!(memories.len() <= 1);
-        if let Some(memory) = memories.get(0) {
+        if let Some(memory) = memories.first() {
             if let Some(i) = &memory.import {
                 Err(Trap::unknown_import(i, "memory", memory.start))
             } else {

wain-exec/src/runtime.rs

@@ -99,7 +99,7 @@ impl<'m, 's, I: Importer> Runtime<'m, 's, I> {
 
                     let fty = &module.types[func.idx as usize];
                     let name = &i.name.0;
-                    match importer.validate(name, &fty.params, fty.results.get(0).copied()) {
+                    match importer.validate(name, &fty.params, fty.results.first().copied()) {
                         Some(ImportInvalidError::NotFound) => {
                             return Err(unknown_import(i, func.start));
                         }

wain-exec/src/stack.rs

@@ -1,6 +1,5 @@
 use crate::value::{LittleEndian, Value};
 use std::cmp::Ordering;
-use std::convert::{TryFrom, TryInto};
 use std::fmt;
 use std::mem;
 use std::mem::size_of;

wain-exec/src/table.rs

@@ -13,7 +13,7 @@ impl Table {
     pub fn allocate(tables: &[ast::Table]) -> Result<Self> {
         // Note: Only one table exists thanks to validation
         assert!(tables.len() <= 1);
-        if let Some(table) = tables.get(0) {
+        if let Some(table) = tables.first() {
             if let Some(i) = &table.import {
                 Err(Trap::unknown_import(i, "table", table.start))
             } else {

wain-exec/src/value.rs

@@ -1,4 +1,3 @@
-use std::convert::{TryFrom, TryInto};
 use std::fmt;
 use std::mem::size_of;
 use std::ops;

wain-syntax-binary/src/leb128.rs

@@ -177,7 +177,7 @@ mod tests {
 
     #[test]
     fn u32_value_ok() {
-        for (input, expected) in vec![
+        for (input, expected) in [
             (vec![0x00], 0),
             (vec![0x80, 0x01], 128),
             (vec![0xc0, 0xc4, 0x07], 123456),

wain-syntax-binary/src/parser.rs

@@ -2,7 +2,6 @@ use crate::error::{Error, ErrorKind, Result};
 use crate::leb128::Leb128;
 use crate::source::BinarySource;
 use std::borrow::Cow;
-use std::convert::TryInto;
 use std::marker::PhantomData;
 use std::str;
 use wain_ast::*;

wain-validate/src/insn.rs

@@ -252,7 +252,7 @@ pub(crate) fn validate_func_body<'outer, S: Source>(
 ) -> Result<(), S> {
     // Note: FuncType already validated func_ty has at most one result type
     // This assumes a function can have only one return value
-    let ret_ty = func_ty.results.get(0).copied();
+    let ret_ty = func_ty.results.first().copied();
     let mut ctx = FuncBodyContext {
         current_op: "",
         current_offset: start,