Couple of fixes

src/func.rs

@@ -1,7 +1,6 @@
 use std::rc::{Rc, Weak};
 use std::fmt;
 use std::collections::HashMap;
-use std::borrow::Cow;
 use parity_wasm::elements::{Local, Opcodes};
 use {Error, Signature};
 use host::Externals;
@@ -99,8 +98,8 @@ impl FuncInstance {
 	}
 
 	pub(crate) fn invoke<E: Externals>(
-		func: FuncRef,
-		args: Cow<[RuntimeValue]>,
+		func: &FuncRef,
+		args: &[RuntimeValue],
 		externals: &mut E,
 	) -> Result<Option<RuntimeValue>, Error> {
 		enum InvokeKind<'a> {

src/memory.rs

@@ -84,7 +84,7 @@ impl MemoryInstance {
 			None => u32::MAX,
 		};
 		let initial_size = calculate_memory_size(0, limits.initial(), maximum_size)
-			.ok_or(Error::Memory(format!("initial memory size must be at most {} pages", LINEAR_MEMORY_MAX_PAGES)))?;
+			.ok_or_else(|| Error::Memory(format!("initial memory size must be at most {} pages", LINEAR_MEMORY_MAX_PAGES)))?;
 
 		let memory = MemoryInstance {
 			limits: limits,
@@ -165,7 +165,7 @@ impl MemoryInstance {
 		where B: ::std::ops::Deref<Target=Vec<u8>>
 	{
 		let end = offset.checked_add(size)
-			.ok_or(Error::Memory(format!("trying to access memory block of size {} from offset {}", size, offset)))?;
+			.ok_or_else(|| Error::Memory(format!("trying to access memory block of size {} from offset {}", size, offset)))?;
 
 		if end > buffer.len() {
 			return Err(Error::Memory(format!("trying to access region [{}..{}] in memory [0..{}]", offset, end, buffer.len())));

src/module.rs

@@ -2,7 +2,6 @@ use std::rc::Rc;
 use std::cell::RefCell;
 use std::fmt;
 use std::collections::HashMap;
-use std::borrow::Cow;
 use parity_wasm::elements::{External, InitExpr, Internal, Opcode, ResizableLimits, Type};
 use {LoadedModule, Error, Signature, MemoryInstance, RuntimeValue, TableInstance};
 use imports::ImportResolver;
@@ -165,7 +164,7 @@ impl ModuleInstance {
 		let instance = ModuleRef(Rc::new(ModuleInstance::default()));
 
 		for &Type::Function(ref ty) in module.type_section().map(|ts| ts.types()).unwrap_or(&[]) {
-			let signature = Rc::new(Signature::from_elements(ty.clone()));
+			let signature = Rc::new(Signature::from_elements(ty));
 			instance.push_signature(signature);
 		}
 
@@ -174,9 +173,9 @@ impl ModuleInstance {
 				&[],
 			);
 			if imports.len() != extern_vals.len() {
-				return Err(Error::Instantiation(format!(
-					"extern_vals length is not equal to import section entries"
-				)));
+				return Err(Error::Instantiation(
+					"extern_vals length is not equal to import section entries".to_owned()
+				));
 			}
 
 			for (import, extern_val) in
@@ -386,7 +385,7 @@ impl ModuleInstance {
 					let &Type::Function(ref func_type) = types
 						.get(fn_ty_idx as usize)
 						.expect("Due to validation functions should have valid types");
-					let signature = Signature::from_elements(func_type.clone());
+					let signature = Signature::from_elements(func_type);
 					let func = imports.resolve_func(module_name, field_name, &signature)?;
 					ExternVal::Func(func)
 				}
@@ -437,7 +436,7 @@ impl ModuleInstance {
 			}
 		};
 
-		FuncInstance::invoke(func_instance.clone(), Cow::Borrowed(args), externals)
+		FuncInstance::invoke(&func_instance, args, externals)
 	}
 }
 
@@ -451,12 +450,12 @@ impl<'a> NotStartedModuleRef<'a> {
 		&self.instance
 	}
 
-	pub fn run_start<'b, E: Externals>(self, state: &'b mut E) -> Result<ModuleRef, Error> {
+	pub fn run_start<E: Externals>(self, state: &mut E) -> Result<ModuleRef, Error> {
 		if let Some(start_fn_idx) = self.loaded_module.module().start_section() {
 			let start_func = self.instance.func_by_index(start_fn_idx).expect(
 				"Due to validation start function should exists",
 			);
-			FuncInstance::invoke(start_func, Cow::Borrowed(&[]), state)?;
+			FuncInstance::invoke(&start_func, &[], state)?;
 		}
 		Ok(self.instance)
 	}

src/runner.rs

@@ -107,7 +107,7 @@ impl<'a, E: Externals> Interpreter<'a, E> {
 						},
 						FuncInstanceInternal::Host { ref signature, .. } => {
 							let args = prepare_function_args(signature, &mut function_context.value_stack)?;
-							let return_val = FuncInstance::invoke(nested_func.clone(), args.into(), self.externals)?;
+							let return_val = FuncInstance::invoke(&nested_func, &args, self.externals)?;
 							if let Some(return_val) = return_val {
 								function_context.value_stack_mut().push(return_val)?;
 							}
@@ -407,7 +407,7 @@ impl<'a, E: Externals> Interpreter<'a, E> {
 		}
 	}
 
-	fn run_br_table(&mut self, context: &mut FunctionContext, table: &Vec<u32>, default: u32) -> Result<InstructionOutcome, Error> {
+	fn run_br_table(&mut self, context: &mut FunctionContext, table: &[u32], default: u32) -> Result<InstructionOutcome, Error> {
 		let index: u32 = context.value_stack_mut().pop_as()?;
 		Ok(InstructionOutcome::Branch(table.get(index as usize).cloned().unwrap_or(default) as usize))
 	}
@@ -1004,7 +1004,7 @@ impl<'a, E: Externals> Interpreter<'a, E> {
 }
 
 impl FunctionContext {
-	pub fn new<'store>(function: FuncRef, value_stack_limit: usize, frame_stack_limit: usize, signature: &Signature, args: Vec<RuntimeValue>) -> Self {
+	pub fn new(function: FuncRef, value_stack_limit: usize, frame_stack_limit: usize, signature: &Signature, args: Vec<RuntimeValue>) -> Self {
 		let module = match *function.as_internal() {
 			FuncInstanceInternal::Internal { ref module, .. } => module.upgrade().expect("module deallocated"),
 			FuncInstanceInternal::Host { .. } => panic!("Host functions can't be called as internally defined functions; Thus FunctionContext can be created only with internally defined functions; qed"),
@@ -1029,7 +1029,7 @@ impl FunctionContext {
 			};
 			let function_type = function.signature();
 			let function_return_type = function_type.return_type().map(|vt| BlockType::Value(vt.into_elements())).unwrap_or(BlockType::NoResult);
-			let function_locals = prepare_function_args(&function_type, &mut self.value_stack)?;
+			let function_locals = prepare_function_args(function_type, &mut self.value_stack)?;
 			(function_locals, module, function_return_type)
 		};
 
@@ -1055,7 +1055,7 @@ impl FunctionContext {
 
 		let locals = locals.iter()
 			.flat_map(|l| repeat(l.value_type()).take(l.count() as usize))
-			.map(|vt| RuntimeValue::default(vt))
+			.map(RuntimeValue::default)
 			.collect::<Vec<_>>();
 		self.locals.extend(locals);
 	}

src/table.rs

@@ -99,7 +99,7 @@ impl TableInstance {
 				buffer_len
 			)),
 		)?;
-		Ok(table_elem.ok_or(Error::Table(format!(
+		Ok(table_elem.ok_or_else(|| Error::Table(format!(
 			"trying to read uninitialized element on index {}",
 			offset
 		)))?)

src/types.rs

@@ -23,7 +23,7 @@ impl Signature {
 		self.return_type
 	}
 
-	pub(crate) fn from_elements(func_type: FunctionType) -> Signature {
+	pub(crate) fn from_elements(func_type: &FunctionType) -> Signature {
 		Signature {
 			params: func_type.params().iter().cloned().map(ValueType::from_elements).collect(),
 			return_type: func_type.return_type().map(ValueType::from_elements),

src/value.rs

@@ -180,7 +180,7 @@ impl TryInto<bool, Error> for RuntimeValue {
 	fn try_into(self) -> Result<bool, Error> {
 		match self {
 			RuntimeValue::I32(val) => Ok(val != 0),
-			_ => Err(Error::Value(format!("32-bit int value expected"))),
+			_ => Err(Error::Value("32-bit int value expected".to_owned())),
 		}
 	}
 }
@@ -189,7 +189,7 @@ impl TryInto<i32, Error> for RuntimeValue {
 	fn try_into(self) -> Result<i32, Error> {
 		match self {
 			RuntimeValue::I32(val) => Ok(val),
-			_ => Err(Error::Value(format!("32-bit int value expected"))),
+			_ => Err(Error::Value("32-bit int value expected".to_owned())),
 		}
 	}
 }
@@ -198,7 +198,7 @@ impl TryInto<i64, Error> for RuntimeValue {
 	fn try_into(self) -> Result<i64, Error> {
 		match self {
 			RuntimeValue::I64(val) => Ok(val),
-			_ => Err(Error::Value(format!("64-bit int value expected"))),
+			_ => Err(Error::Value("64-bit int value expected".to_owned())),
 		}
 	}
 }
@@ -207,7 +207,7 @@ impl TryInto<f32, Error> for RuntimeValue {
 	fn try_into(self) -> Result<f32, Error> {
 		match self {
 			RuntimeValue::F32(val) => Ok(val),
-			_ => Err(Error::Value(format!("32-bit float value expected"))),
+			_ => Err(Error::Value("32-bit float value expected".to_owned())),
 		}
 	}
 }
@@ -216,7 +216,7 @@ impl TryInto<f64, Error> for RuntimeValue {
 	fn try_into(self) -> Result<f64, Error> {
 		match self {
 			RuntimeValue::F64(val) => Ok(val),
-			_ => Err(Error::Value(format!("64-bit float value expected"))),
+			_ => Err(Error::Value("64-bit float value expected".to_owned())),
 		}
 	}
 }
@@ -225,7 +225,7 @@ impl TryInto<u32, Error> for RuntimeValue {
 	fn try_into(self) -> Result<u32, Error> {
 		match self {
 			RuntimeValue::I32(val) => Ok(val as u32),
-			_ => Err(Error::Value(format!("32-bit int value expected"))),
+			_ => Err(Error::Value("32-bit int value expected".to_owned())),
 		}
 	}
 }
@@ -234,7 +234,7 @@ impl TryInto<u64, Error> for RuntimeValue {
 	fn try_into(self) -> Result<u64, Error> {
 		match self {
 			RuntimeValue::I64(val) => Ok(val as u64),
-			_ => Err(Error::Value(format!("64-bit int value expected"))),
+			_ => Err(Error::Value("64-bit int value expected".to_owned())),
 		}
 	}
 }
@@ -379,7 +379,7 @@ impl LittleEndianConvert for i8 {
 	fn from_little_endian(buffer: Vec<u8>) -> Result<Self, Error> {
 		buffer.get(0)
 			.map(|v| *v as i8)
-			.ok_or(Error::Value("invalid little endian buffer".into()))
+			.ok_or_else(|| Error::Value("invalid little endian buffer".into()))
 	}
 }
 
@@ -391,7 +391,7 @@ impl LittleEndianConvert for u8 {
 	fn from_little_endian(buffer: Vec<u8>) -> Result<Self, Error> {
 		buffer.get(0)
 			.cloned()
-			.ok_or(Error::Value("invalid little endian buffer".into()))
+			.ok_or_else(|| Error::Value("invalid little endian buffer".into()))
 	}
 }