Fix a number of warnings on nightly Rust (#2652)

This fixes some issues that are cropping up where some syntax will get
phased out in 2021

cranelift/codegen/meta/src/cdsl/ast.rs

@@ -296,7 +296,8 @@ impl Var {
     pub fn set_def(&mut self, position: PatternPosition, def: DefIndex) {
         assert!(
             self.get_def(position).is_none(),
-            format!("redefinition of variable {}", self.name)
+            "redefinition of variable {}",
+            self.name
         );
         match position {
             PatternPosition::Source => {
@@ -461,7 +462,8 @@ impl Apply {
         // Basic check on number of arguments.
         assert!(
             inst.operands_in.len() == args.len(),
-            format!("incorrect number of arguments in instruction {}", inst.name)
+            "incorrect number of arguments in instruction {}",
+            inst.name
         );
 
         // Check that the kinds of Literals arguments match the expected operand.

cranelift/codegen/meta/src/cdsl/encodings.rs

@@ -153,10 +153,9 @@ impl EncodingBuilder {
         let inst = self.inst.inst();
         assert!(
             Rc::ptr_eq(&inst.format, &recipes[self.recipe].format),
-            format!(
             "Inst {} and recipe {} must have the same format!",
-                inst.name, recipes[self.recipe].name
+            inst.name,
-            )
+            recipes[self.recipe].name
         );
 
         assert_eq!(

cranelift/codegen/meta/src/cdsl/instructions.rs

@@ -394,7 +394,7 @@ impl ValueTypeOrAny {
     pub fn expect(self, msg: &str) -> ValueType {
         match self {
             ValueTypeOrAny::ValueType(vt) => vt,
-            ValueTypeOrAny::Any => panic!(format!("Unexpected Any: {}", msg)),
+            ValueTypeOrAny::Any => panic!("Unexpected Any: {}", msg),
         }
     }
 }
@@ -665,7 +665,7 @@ fn verify_polymorphic(
     if operands_out.is_empty() {
         // No result means no other possible type variable, so it's a type inference failure.
         match maybe_error_message {
-            Some(msg) => panic!(msg),
+            Some(msg) => panic!("{}", msg),
             None => panic!("typevar_operand must be a free type variable"),
         }
     }

cranelift/codegen/meta/src/cdsl/recipes.rs

@@ -260,10 +260,9 @@ impl EncodingRecipeBuilder {
         if !self.format.has_value_list {
             assert!(
                 operands_in.len() == self.format.num_value_operands,
-                format!(
                 "missing operand constraints for recipe {} (format {})",
-                    self.name, self.format.name
+                self.name,
-                )
+                self.format.name
             );
         }
 

cranelift/codegen/meta/src/cdsl/type_inference.rs

@@ -210,7 +210,8 @@ impl TypeEnvironment {
                 None => {
                     assert!(
                         !actual_tv.name.starts_with("typeof_"),
-                        format!("variable {} should be explicitly ranked", actual_tv.name)
+                        "variable {} should be explicitly ranked",
+                        actual_tv.name
                     );
                     None
                 }

cranelift/codegen/meta/src/cdsl/xform.rs

@@ -74,19 +74,18 @@ impl Transform {
         for &var_index in &input_vars {
             assert!(
                 var_pool.get(var_index).is_input(),
-                format!("'{:?}' used as both input and def", var_pool.get(var_index))
+                "'{:?}' used as both input and def",
+                var_pool.get(var_index)
             );
         }
         assert!(
             input_vars.len() == num_src_inputs,
-            format!(
             "extra input vars in dst pattern: {:?}",
             input_vars
                 .iter()
                 .map(|&i| var_pool.get(i))
                 .skip(num_src_inputs)
                 .collect::<Vec<_>>()
-            )
         );
 
         // Perform type inference and cleanup.
@@ -143,7 +142,8 @@ impl Transform {
             let defined_var = self.var_pool.get(var_index);
             assert!(
                 defined_var.is_output(),
-                format!("{:?} not defined in the destination pattern", defined_var)
+                "{:?} not defined in the destination pattern",
+                defined_var
             );
         }
     }
@@ -226,7 +226,8 @@ fn rewrite_expr(
                 let var = var_pool.get(own_var);
                 assert!(
                     var.is_input() || var.get_def(position).is_some(),
-                    format!("{:?} used as both input and def", var)
+                    "{:?} used as both input and def",
+                    var
                 );
                 args.push(Expr::Var(own_var));
             }
@@ -400,10 +401,8 @@ impl TransformGroupBuilder {
             self.custom_legalizes
                 .insert(inst.camel_name.clone(), func_name)
                 .is_none(),
-            format!(
             "custom legalization action for {} inserted twice",
             inst.name
-            )
         );
     }
 
@@ -442,7 +441,8 @@ impl TransformGroups {
         for group in self.groups.values() {
             assert!(
                 group.name != new_group.name,
-                format!("trying to insert {} for the second time", new_group.name)
+                "trying to insert {} for the second time",
+                new_group.name
             );
         }
         self.groups.push(new_group)
@@ -459,7 +459,7 @@ impl TransformGroups {
                 return group;
             }
         }
-        panic!(format!("transform group with name {} not found", name));
+        panic!("transform group with name {} not found", name);
     }
 }
 

cranelift/codegen/meta/src/gen_encodings.rs

@@ -99,8 +99,8 @@ fn emit_instp(instp: &InstructionPredicate, has_func: bool, fmt: &mut Formatter)
                 Some(previous_format_name) => {
                     assert!(
                         previous_format_name == leaf_format_name,
-                        format!("Format predicate can only operate on a single InstructionFormat; trying to use both {} and {}", previous_format_name, leaf_format_name
+                        "Format predicate can only operate on a single InstructionFormat; trying to use both {} and {}", previous_format_name, leaf_format_name
-                    ));
+                    );
                 }
             }
         }

cranelift/codegen/meta/src/isa/riscv/recipes.rs

@@ -25,7 +25,8 @@ impl RecipeGroup {
     fn push(&mut self, builder: EncodingRecipeBuilder) {
         assert!(
             self.name_to_recipe.get(&builder.name).is_none(),
-            format!("riscv recipe '{}' created twice", builder.name)
+            "riscv recipe '{}' created twice",
+            builder.name
         );
         let name = builder.name.clone();
         let number = self.recipes.push(builder.build());

cranelift/codegen/meta/src/isa/x86/encodings.rs

@@ -45,10 +45,8 @@ impl PerCpuModeEncodings {
         if let Some(found_index) = self.recipes_by_name.get(&recipe.name) {
             assert!(
                 self.recipes[*found_index] == recipe,
-                format!(
                 "trying to insert different recipes with a same name ({})",
                 recipe.name
-                )
             );
             *found_index
         } else {