Loop over references to containers instead of using explicit iteration methods.

https://github.com/rust-lang-nursery/rust-clippy/wiki#explicit_iter_loop

lib/frontend/src/frontend.rs

@@ -492,7 +492,7 @@ impl<'a, Variable> FunctionBuilder<'a, Variable>
 
     fn fill_function_args_values(&mut self, ebb: Ebb) {
         debug_assert!(self.pristine);
-        for argtyp in self.func.signature.argument_types.iter() {
+        for argtyp in &self.func.signature.argument_types {
             self.builder
                 .function_args_values
                 .push(self.func.dfg.append_ebb_arg(ebb, argtyp.value_type));

lib/frontend/src/ssa.rs

@@ -402,7 +402,7 @@ impl<Variable> SSABuilder<Variable>
         };
         // For each undef var we look up values in the predecessors and create an Ebb argument
         // only if necessary.
-        for &(var, val) in undef_vars.iter() {
+        for &(var, val) in &undef_vars {
             let (_, mut local_side_effects) =
                 self.predecessors_lookup(dfg, layout, jts, val, var, ebb, &predecessors);
             side_effects

lib/wasm/src/code_translator.rs

@@ -506,7 +506,7 @@ fn translate_operator(op: &Operator,
         Operator::BrTable { ref table } => {
             let (depths, default) = table.read_table();
             let mut min_depth = default;
-            for depth in depths.iter() {
+            for depth in &depths {
                 if *depth < min_depth {
                     min_depth = *depth;
                 }

lib/wasm/src/translation_utils.rs

@@ -142,10 +142,10 @@ pub fn translate_type(ty: wasmparser::Type) -> Result<Vec<cretonne::ir::Type>, (
 pub fn invert_hashmaps(imports: code_translator::FunctionImports)
                        -> module_translator::ImportMappings {
     let mut new_imports = module_translator::ImportMappings::new();
-    for (func_index, func_ref) in imports.functions.iter() {
+    for (func_index, func_ref) in &imports.functions {
         new_imports.functions.insert(*func_ref, *func_index);
     }
-    for (sig_index, sig_ref) in imports.signatures.iter() {
+    for (sig_index, sig_ref) in &imports.signatures {
         new_imports.signatures.insert(*sig_ref, *sig_index);
     }
     new_imports