Prevent re-allocation in CallableSig::from_params_and_return

Author: Veykril

src/tools/rust-analyzer/crates/hir-ty/src/lib.rs

@@ -513,14 +513,16 @@ pub type PolyFnSig = Binders<CallableSig>;
 
 impl CallableSig {
     pub fn from_params_and_return(
-        mut params: Vec<Ty>,
+        params: impl ExactSizeIterator<Item = Ty>,
         ret: Ty,
         is_varargs: bool,
         safety: Safety,
         abi: FnAbi,
     ) -> CallableSig {
-        params.push(ret);
-        CallableSig { params_and_return: params.into(), is_varargs, safety, abi }
+        let mut params_and_return = Vec::with_capacity(params.len() + 1);
+        params_and_return.extend(params);
+        params_and_return.push(ret);
+        CallableSig { params_and_return: params_and_return.into(), is_varargs, safety, abi }
     }
 
     pub fn from_def(db: &dyn HirDatabase, def: FnDefId, substs: &Substitution) -> CallableSig {
@@ -935,8 +937,7 @@ pub fn callable_sig_from_fn_trait(
                     .as_tuple()?
                     .iter(Interner)
                     .map(|it| it.assert_ty_ref(Interner))
-                    .cloned()
-                    .collect();
+                    .cloned();
 
                 return Some((
                     fn_x,

src/tools/rust-analyzer/crates/hir-ty/src/lower.rs

@@ -1855,7 +1855,7 @@ fn fn_sig_for_fn(db: &dyn HirDatabase, def: FunctionId) -> PolyFnSig {
     let ctx_params = TyLoweringContext::new(db, &resolver, def.into())
         .with_impl_trait_mode(ImplTraitLoweringMode::Variable)
         .with_type_param_mode(ParamLoweringMode::Variable);
-    let params = data.params.iter().map(|tr| ctx_params.lower_ty(tr)).collect::<Vec<_>>();
+    let params = data.params.iter().map(|tr| ctx_params.lower_ty(tr));
     let ctx_ret = TyLoweringContext::new(db, &resolver, def.into())
         .with_impl_trait_mode(ImplTraitLoweringMode::Opaque)
         .with_type_param_mode(ParamLoweringMode::Variable);
@@ -1909,7 +1909,7 @@ fn fn_sig_for_struct_constructor(db: &dyn HirDatabase, def: StructId) -> PolyFnS
     let resolver = def.resolver(db.upcast());
     let ctx = TyLoweringContext::new(db, &resolver, AdtId::from(def).into())
         .with_type_param_mode(ParamLoweringMode::Variable);
-    let params = fields.iter().map(|(_, field)| ctx.lower_ty(&field.type_ref)).collect::<Vec<_>>();
+    let params = fields.iter().map(|(_, field)| ctx.lower_ty(&field.type_ref));
     let (ret, binders) = type_for_adt(db, def.into()).into_value_and_skipped_binders();
     Binders::new(
         binders,
@@ -1941,7 +1941,7 @@ fn fn_sig_for_enum_variant_constructor(db: &dyn HirDatabase, def: EnumVariantId)
     let resolver = def.resolver(db.upcast());
     let ctx = TyLoweringContext::new(db, &resolver, DefWithBodyId::VariantId(def).into())
         .with_type_param_mode(ParamLoweringMode::Variable);
-    let params = fields.iter().map(|(_, field)| ctx.lower_ty(&field.type_ref)).collect::<Vec<_>>();
+    let params = fields.iter().map(|(_, field)| ctx.lower_ty(&field.type_ref));
     let (ret, binders) =
         type_for_adt(db, def.lookup(db.upcast()).parent.into()).into_value_and_skipped_binders();
     Binders::new(