redundant closure implemented for closures containing method calls

Grzegorz · Grzegorz · commit b38c587b9805 · 2019-02-10T12:58:51.000+01:00
diff --git a/clippy_lints/src/eta_reduction.rs b/clippy_lints/src/eta_reduction.rs
@@ -1,4 +1,5 @@
-use crate::utils::{is_adjusted, iter_input_pats, snippet_opt, span_lint_and_then};
+use crate::utils::{is_adjusted, iter_input_pats, snippet_opt, span_lint_and_then, type_is_unsafe_function};
+use if_chain::if_chain;
 use rustc::hir::*;
 use rustc::lint::{LateContext, LateLintPass, LintArray, LintPass};
 use rustc::ty;
@@ -59,56 +60,136 @@ fn check_closure(cx: &LateContext<'_, '_>, expr: &Expr) {
     if let ExprKind::Closure(_, ref decl, eid, _, _) = expr.node {
         let body = cx.tcx.hir().body(eid);
         let ex = &body.value;
-        if let ExprKind::Call(ref caller, ref args) = ex.node {
-            if args.len() != decl.inputs.len() {
-                // Not the same number of arguments, there
-                // is no way the closure is the same as the function
-                return;
-            }
-            if is_adjusted(cx, ex) || args.iter().any(|arg| is_adjusted(cx, arg)) {
-                // Are the expression or the arguments type-adjusted? Then we need the closure
-                return;
-            }
+
+        if_chain!(
+            if let ExprKind::Call(ref caller, ref args) = ex.node;
+
+            // Not the same number of arguments, there is no way the closure is the same as the function return;
+            if args.len() == decl.inputs.len();
+
+            // Are the expression or the arguments type-adjusted? Then we need the closure
+            if !(is_adjusted(cx, ex) || args.iter().any(|arg| is_adjusted(cx, arg)));
+
             let fn_ty = cx.tables.expr_ty(caller);
-            match fn_ty.sty {
-                // Is it an unsafe function? They don't implement the closure traits
-                ty::FnDef(..) | ty::FnPtr(_) => {
-                    let sig = fn_ty.fn_sig(cx.tcx);
-                    if sig.skip_binder().unsafety == Unsafety::Unsafe || sig.skip_binder().output().sty == ty::Never {
-                        return;
+            if !type_is_unsafe_function(cx, fn_ty);
+
+            if compare_inputs(&mut iter_input_pats(decl, body), &mut args.into_iter());
+
+            then {
+                span_lint_and_then(cx, REDUNDANT_CLOSURE, expr.span, "redundant closure found", |db| {
+                    if let Some(snippet) = snippet_opt(cx, caller.span) {
+                        db.span_suggestion(
+                            expr.span,
+                            "remove closure as shown",
+                            snippet,
+                            Applicability::MachineApplicable,
+                        );
                     }
-                },
-                _ => (),
+                });
             }
-            for (a1, a2) in iter_input_pats(decl, body).zip(args) {
-                if let PatKind::Binding(.., ident, _) = a1.pat.node {
-                    // XXXManishearth Should I be checking the binding mode here?
-                    if let ExprKind::Path(QPath::Resolved(None, ref p)) = a2.node {
-                        if p.segments.len() != 1 {
-                            // If it's a proper path, it can't be a local variable
-                            return;
-                        }
-                        if p.segments[0].ident.name != ident.name {
-                            // The two idents should be the same
-                            return;
-                        }
-                    } else {
-                        return;
-                    }
-                } else {
-                    return;
-                }
-            }
-            span_lint_and_then(cx, REDUNDANT_CLOSURE, expr.span, "redundant closure found", |db| {
-                if let Some(snippet) = snippet_opt(cx, caller.span) {
+        );
+
+        if_chain!(
+            if let ExprKind::MethodCall(ref path, _, ref args) = ex.node;
+
+            // Not the same number of arguments, there is no way the closure is the same as the function return;
+            if args.len() == decl.inputs.len();
+
+            // Are the expression or the arguments type-adjusted? Then we need the closure
+            if !(is_adjusted(cx, ex) || args.iter().skip(1).any(|arg| is_adjusted(cx, arg)));
+
+            let method_def_id = cx.tables.type_dependent_defs()[ex.hir_id].def_id();
+            if !type_is_unsafe_function(cx, cx.tcx.type_of(method_def_id));
+
+            if compare_inputs(&mut iter_input_pats(decl, body), &mut args.into_iter());
+
+            if let Some(name) = get_ufcs_type_name(cx, method_def_id, &args[0]);
+
+            then {
+                span_lint_and_then(cx, REDUNDANT_CLOSURE, expr.span, "redundant closure found", |db| {
                     db.span_suggestion(
                         expr.span,
                         "remove closure as shown",
-                        snippet,
+                        format!("{}::{}", name, path.ident.name),
                         Applicability::MachineApplicable,
                     );
+                });
+            }
+        );
+    }
+}
+
+/// Tries to determine the type for universal function call to be used instead of the closure
+fn get_ufcs_type_name(
+    cx: &LateContext<'_, '_>,
+    method_def_id: def_id::DefId,
+    self_arg: &Expr,
+) -> std::option::Option<String> {
+    let expected_type_of_self = &cx.tcx.fn_sig(method_def_id).inputs_and_output().skip_binder()[0].sty;
+    let actual_type_of_self = &cx.tables.node_id_to_type(self_arg.hir_id).sty;
+
+    if let Some(trait_id) = cx.tcx.trait_of_item(method_def_id) {
+        //if the method expectes &self, ufcs requires explicit borrowing so closure can't be removed
+        return match (expected_type_of_self, actual_type_of_self) {
+            (ty::Ref(_, _, _), ty::Ref(_, _, _)) => Some(cx.tcx.item_path_str(trait_id)),
+            (l, r) => match (l, r) {
+                (ty::Ref(_, _, _), _) | (_, ty::Ref(_, _, _)) => None,
+                (_, _) => Some(cx.tcx.item_path_str(trait_id)),
+            },
+        };
+    }
+
+    cx.tcx.impl_of_method(method_def_id).and_then(|_| {
+        //a type may implicitly implement other types methods (e.g. Deref)
+        if match_types(expected_type_of_self, actual_type_of_self) {
+            return Some(get_type_name(cx, &actual_type_of_self));
+        }
+        None
+    })
+}
+
+fn match_types(lhs: &ty::TyKind<'_>, rhs: &ty::TyKind<'_>) -> bool {
+    match (lhs, rhs) {
+        (ty::Bool, ty::Bool)
+        | (ty::Char, ty::Char)
+        | (ty::Int(_), ty::Int(_))
+        | (ty::Uint(_), ty::Uint(_))
+        | (ty::Str, ty::Str) => true,
+        (ty::Ref(_, t1, _), ty::Ref(_, t2, _))
+        | (ty::Array(t1, _), ty::Array(t2, _))
+        | (ty::Slice(t1), ty::Slice(t2)) => match_types(&t1.sty, &t2.sty),
+        (ty::Adt(def1, _), ty::Adt(def2, _)) => def1 == def2,
+        (_, _) => false,
+    }
+}
+
+fn get_type_name(cx: &LateContext<'_, '_>, kind: &ty::TyKind<'_>) -> String {
+    match kind {
+        ty::Adt(t, _) => cx.tcx.item_path_str(t.did),
+        ty::Ref(_, r, _) => get_type_name(cx, &r.sty),
+        _ => kind.to_string(),
+    }
+}
+
+fn compare_inputs(closure_inputs: &mut dyn Iterator<Item = &Arg>, call_args: &mut dyn Iterator<Item = &Expr>) -> bool {
+    for (closure_input, function_arg) in closure_inputs.zip(call_args) {
+        if let PatKind::Binding(_, _, _, ident, _) = closure_input.pat.node {
+            // XXXManishearth Should I be checking the binding mode here?
+            if let ExprKind::Path(QPath::Resolved(None, ref p)) = function_arg.node {
+                if p.segments.len() != 1 {
+                    // If it's a proper path, it can't be a local variable
+                    return false;
                 }
-            });
+                if p.segments[0].ident.name != ident.name {
+                    // The two idents should be the same
+                    return false;
+                }
+            } else {
+                return false;
+            }
+        } else {
+            return false;
         }
     }
+    true
 }
diff --git a/tests/ui/eta.rs b/tests/ui/eta.rs
@@ -9,6 +9,8 @@
 )]
 #![warn(clippy::redundant_closure, clippy::needless_borrow)]
 
+use std::path::PathBuf;
+
 fn main() {
     let a = Some(1u8).map(|a| foo(a));
     meta(|a| foo(a));
@@ -26,6 +28,57 @@ fn main() {
     // See #515
     let a: Option<Box<::std::ops::Deref<Target = [i32]>>> =
         Some(vec![1i32, 2]).map(|v| -> Box<::std::ops::Deref<Target = [i32]>> { Box::new(v) });
+
+}
+
+trait TestTrait {
+    fn trait_foo(self) -> bool;
+    fn trait_foo_ref(&self) -> bool;
+}
+
+struct TestStruct<'a> {
+    some_ref: &'a i32
+}
+
+impl<'a> TestStruct<'a> {
+    fn foo(self) -> bool { false }
+    unsafe fn foo_unsafe(self) -> bool { true }
+}
+
+impl<'a> TestTrait for TestStruct<'a> {
+    fn trait_foo(self) -> bool { false }
+    fn trait_foo_ref(&self) -> bool { false }
+}
+
+impl<'a> std::ops::Deref for TestStruct<'a> {
+    type Target = char;
+    fn deref(&self) -> &char { &'a' }
+}
+
+fn test_redundant_closures_containing_method_calls() {
+    let i = 10;
+    let e = Some(TestStruct{some_ref: &i}).map(|a| a.foo());
+    let e = Some(TestStruct{some_ref: &i}).map(TestStruct::foo);
+    let e = Some(TestStruct{some_ref: &i}).map(|a| a.trait_foo());
+    let e = Some(TestStruct{some_ref: &i}).map(|a| a.trait_foo_ref());
+    let e = Some(TestStruct{some_ref: &i}).map(TestTrait::trait_foo);
+    let e = Some(&mut vec!(1,2,3)).map(|v| v.clear());
+    let e = Some(&mut vec!(1,2,3)).map(std::vec::Vec::clear);
+    unsafe {
+        let e = Some(TestStruct{some_ref: &i}).map(|a| a.foo_unsafe());
+    }
+    let e = Some("str").map(|s| s.to_string());
+    let e = Some("str").map(str::to_string);
+    let e = Some('a').map(|s| s.to_uppercase());
+    let e = Some('a').map(char::to_uppercase);
+    let e: std::vec::Vec<usize> = vec!('a','b','c').iter().map(|c| c.len_utf8()).collect();
+    let e: std::vec::Vec<char> = vec!('a','b','c').iter().map(|c| c.to_ascii_uppercase()).collect();
+    let e: std::vec::Vec<char> = vec!('a','b','c').iter().map(char::to_ascii_uppercase).collect();
+    let p = Some(PathBuf::new());
+    let e = p.as_ref().and_then(|s| s.to_str());
+    //let e = p.as_ref().and_then(std::path::Path::to_str);
+    let c = Some(TestStruct{some_ref: &i}).as_ref().map(|c| c.to_ascii_uppercase());
+    //let c = Some(TestStruct{some_ref: &i}).as_ref().map(char::to_ascii_uppercase);
 }
 
 fn meta<F>(f: F)
@@ -61,3 +114,4 @@ fn divergent(_: u8) -> ! {
 fn generic<T>(_: T) -> u8 {
     0
 }
+
diff --git a/tests/ui/eta.stderr b/tests/ui/eta.stderr
@@ -1,36 +1,72 @@
 error: redundant closure found
-  --> $DIR/eta.rs:13:27
+  --> $DIR/eta.rs:15:27
    |
 LL |     let a = Some(1u8).map(|a| foo(a));
    |                           ^^^^^^^^^^ help: remove closure as shown: `foo`
    |
    = note: `-D clippy::redundant-closure` implied by `-D warnings`
 
 error: redundant closure found
-  --> $DIR/eta.rs:14:10
+  --> $DIR/eta.rs:16:10
    |
 LL |     meta(|a| foo(a));
    |          ^^^^^^^^^^ help: remove closure as shown: `foo`
 
 error: redundant closure found
-  --> $DIR/eta.rs:15:27
+  --> $DIR/eta.rs:17:27
    |
 LL |     let c = Some(1u8).map(|a| {1+2; foo}(a));
    |                           ^^^^^^^^^^^^^^^^^ help: remove closure as shown: `{1+2; foo}`
 
 error: this expression borrows a reference that is immediately dereferenced by the compiler
-  --> $DIR/eta.rs:17:21
+  --> $DIR/eta.rs:19:21
    |
 LL |     all(&[1, 2, 3], &&2, |x, y| below(x, y)); //is adjusted
    |                     ^^^ help: change this to: `&2`
    |
    = note: `-D clippy::needless-borrow` implied by `-D warnings`
 
 error: redundant closure found
-  --> $DIR/eta.rs:24:27
+  --> $DIR/eta.rs:26:27
    |
 LL |     let e = Some(1u8).map(|a| generic(a));
    |                           ^^^^^^^^^^^^^^ help: remove closure as shown: `generic`
 
-error: aborting due to 5 previous errors
+error: redundant closure found
+  --> $DIR/eta.rs:60:48
+   |
+LL |     let e = Some(TestStruct{some_ref: &i}).map(|a| a.foo());
+   |                                                ^^^^^^^^^^^ help: remove closure as shown: `TestStruct::foo`
+
+error: redundant closure found
+  --> $DIR/eta.rs:62:48
+   |
+LL |     let e = Some(TestStruct{some_ref: &i}).map(|a| a.trait_foo());
+   |                                                ^^^^^^^^^^^^^^^^^ help: remove closure as shown: `TestTrait::trait_foo`
+
+error: redundant closure found
+  --> $DIR/eta.rs:65:40
+   |
+LL |     let e = Some(&mut vec!(1,2,3)).map(|v| v.clear());
+   |                                        ^^^^^^^^^^^^^ help: remove closure as shown: `std::vec::Vec::clear`
+
+error: redundant closure found
+  --> $DIR/eta.rs:70:29
+   |
+LL |     let e = Some("str").map(|s| s.to_string());
+   |                             ^^^^^^^^^^^^^^^^^ help: remove closure as shown: `std::string::ToString::to_string`
+
+error: redundant closure found
+  --> $DIR/eta.rs:72:27
+   |
+LL |     let e = Some('a').map(|s| s.to_uppercase());
+   |                           ^^^^^^^^^^^^^^^^^^^^ help: remove closure as shown: `char::to_uppercase`
+
+error: redundant closure found
+  --> $DIR/eta.rs:75:63
+   |
+LL |     let e: std::vec::Vec<char> = vec!('a','b','c').iter().map(|c| c.to_ascii_uppercase()).collect();
+   |                                                               ^^^^^^^^^^^^^^^^^^^^^^^^^^ help: remove closure as shown: `char::to_ascii_uppercase`
+
+error: aborting due to 11 previous errors
 
