improve the no_effect lint

Author: oli-obk

src/no_effect.rs

@@ -1,6 +1,6 @@
 use rustc::lint::{LateContext, LateLintPass, LintArray, LintPass};
 use rustc::middle::def::Def;
-use rustc_front::hir::{Expr, ExprCall, ExprLit, ExprPath, ExprStruct};
+use rustc_front::hir::{Expr, Expr_};
 use rustc_front::hir::{Stmt, StmtSemi};
 
 use utils::in_macro;
@@ -24,16 +24,33 @@ fn has_no_effect(cx: &LateContext, expr: &Expr) -> bool {
         return false;
     }
     match expr.node {
-        ExprLit(..) |
-        ExprPath(..) => true,
-        ExprStruct(_, ref fields, ref base) => {
+        Expr_::ExprLit(..) |
+        Expr_::ExprClosure(..) |
+        Expr_::ExprRange(None, None) |
+        Expr_::ExprPath(..) => true,
+        Expr_::ExprIndex(ref a, ref b) |
+        Expr_::ExprRange(Some(ref a), Some(ref b)) |
+        Expr_::ExprBinary(_, ref a, ref b) => has_no_effect(cx, a) && has_no_effect(cx, b),
+        Expr_::ExprVec(ref v) |
+        Expr_::ExprTup(ref v) => v.iter().all(|val| has_no_effect(cx, val)),
+        Expr_::ExprRange(Some(ref inner), None) |
+        Expr_::ExprRange(None, Some(ref inner)) |
+        Expr_::ExprRepeat(ref inner, _) |
+        Expr_::ExprCast(ref inner, _) |
+        Expr_::ExprType(ref inner, _) |
+        Expr_::ExprUnary(_, ref inner) |
+        Expr_::ExprField(ref inner, _) |
+        Expr_::ExprTupField(ref inner, _) |
+        Expr_::ExprAddrOf(_, ref inner) |
+        Expr_::ExprBox(ref inner) => has_no_effect(cx, inner),
+        Expr_::ExprStruct(_, ref fields, ref base) => {
             fields.iter().all(|field| has_no_effect(cx, &field.expr)) &&
             match *base {
                 Some(ref base) => has_no_effect(cx, base),
                 None => true,
             }
         }
-        ExprCall(ref callee, ref args) => {
+        Expr_::ExprCall(ref callee, ref args) => {
             let def = cx.tcx.def_map.borrow().get(&callee.id).map(|d| d.full_def());
             match def {
                 Some(Def::Struct(..)) |

tests/compile-fail/absurd-extreme-comparisons.rs

@@ -2,7 +2,7 @@
 #![plugin(clippy)]
 
 #![deny(absurd_extreme_comparisons)]
-#![allow(unused, eq_op)]
+#![allow(unused, eq_op, no_effect)]
 fn main() {
     const Z: u32 = 0;
 

tests/compile-fail/array_indexing.rs

@@ -2,6 +2,7 @@
 #![plugin(clippy)]
 
 #![deny(out_of_bounds_indexing)]
+#![allow(no_effect)]
 
 fn main() {
     let x = [1,2,3,4];

tests/compile-fail/bit_masks.rs

@@ -5,7 +5,7 @@ const THREE_BITS : i64 = 7;
 const EVEN_MORE_REDIRECTION : i64 = THREE_BITS;
 
 #[deny(bad_bit_mask)]
-#[allow(ineffective_bit_mask, identity_op)]
+#[allow(ineffective_bit_mask, identity_op, no_effect)]
 fn main() {
     let x = 5;
 
@@ -45,7 +45,7 @@ fn main() {
 }
 
 #[deny(ineffective_bit_mask)]
-#[allow(bad_bit_mask)]
+#[allow(bad_bit_mask, no_effect)]
 fn ineffective() {
     let x = 5;
 

tests/compile-fail/cast.rs

@@ -2,6 +2,7 @@
 #![plugin(clippy)]
 
 #[deny(cast_precision_loss, cast_possible_truncation, cast_sign_loss, cast_possible_wrap)]
+#[allow(no_effect)]
 fn main() {
     // Test cast_precision_loss
     1i32 as f32; //~ERROR casting i32 to f32 causes a loss of precision (i32 is 32 bits wide, but f32's mantissa is only 23 bits wide)

tests/compile-fail/cmp_nan.rs

@@ -2,7 +2,7 @@
 #![plugin(clippy)]
 
 #[deny(cmp_nan)]
-#[allow(float_cmp)]
+#[allow(float_cmp, no_effect)]
 fn main() {
     let x = 5f32;
     x == std::f32::NAN; //~ERROR doomed comparison with NAN

tests/compile-fail/copies.rs

@@ -1,7 +1,7 @@
 #![feature(plugin)]
 #![plugin(clippy)]
 
-#![allow(dead_code)]
+#![allow(dead_code, no_effect)]
 #![allow(let_and_return)]
 #![allow(needless_return)]
 #![allow(unused_variables)]

tests/compile-fail/eq_op.rs

@@ -3,6 +3,7 @@
 
 #[deny(eq_op)]
 #[allow(identity_op)]
+#[allow(no_effect)]
 fn main() {
     // simple values and comparisons
     1 == 1; //~ERROR equal expressions

tests/compile-fail/eta.rs

@@ -1,6 +1,6 @@
 #![feature(plugin)]
 #![plugin(clippy)]
-#![allow(unknown_lints, unused)]
+#![allow(unknown_lints, unused, no_effect)]
 #![deny(redundant_closure)]
 
 fn main() {

tests/compile-fail/float_cmp.rs

@@ -2,7 +2,7 @@
 #![plugin(clippy)]
 
 #![deny(float_cmp)]
-#![allow(unused)]
+#![allow(unused, no_effect)]
 
 use std::ops::Add;
 

tests/compile-fail/identity_op.rs

@@ -5,7 +5,7 @@ const ONE : i64 = 1;
 const NEG_ONE : i64 = -1;
 const ZERO : i64 = 0;
 
-#[allow(eq_op)]
+#[allow(eq_op, no_effect)]
 #[deny(identity_op)]
 fn main() {
     let x = 0;

tests/compile-fail/modulo_one.rs

@@ -1,6 +1,7 @@
 #![feature(plugin)]
 #![plugin(clippy)]
 #![deny(modulo_one)]
+#![allow(no_effect)]
 
 fn main() {
     10 % 1; //~ERROR any number modulo 1 will be 0

tests/compile-fail/mut_mut.rs

@@ -1,7 +1,7 @@
 #![feature(plugin)]
 #![plugin(clippy)]
 
-#![allow(unused)]
+#![allow(unused, no_effect)]
 
 //#![plugin(regex_macros)]
 //extern crate regex;

tests/compile-fail/no_effect.rs

@@ -1,4 +1,4 @@
-#![feature(plugin)]
+#![feature(plugin, box_syntax)]
 #![plugin(clippy)]
 
 #![deny(no_effect)]
@@ -20,14 +20,32 @@ fn get_struct() -> Struct { Struct { field: 0 } }
 
 fn main() {
     let s = get_struct();
+    let s2 = get_struct();
 
     0; //~ERROR statement with no effect
+    s2; //~ERROR statement with no effect
     Unit; //~ERROR statement with no effect
     Tuple(0); //~ERROR statement with no effect
     Struct { field: 0 }; //~ERROR statement with no effect
     Struct { ..s }; //~ERROR statement with no effect
     Enum::Tuple(0); //~ERROR statement with no effect
     Enum::Struct { field: 0 }; //~ERROR statement with no effect
+    5 + 6; //~ERROR statement with no effect
+    *&42; //~ERROR statement with no effect
+    &6; //~ERROR statement with no effect
+    (5, 6, 7); //~ERROR statement with no effect
+    box 42; //~ERROR statement with no effect
+    ..; //~ERROR statement with no effect
+    5..; //~ERROR statement with no effect
+    ..5; //~ERROR statement with no effect
+    5..6; //~ERROR statement with no effect
+    [42, 55]; //~ERROR statement with no effect
+    [42, 55][1]; //~ERROR statement with no effect
+    (42, 55).1; //~ERROR statement with no effect
+    [42; 55]; //~ERROR statement with no effect
+    [42; 55][13]; //~ERROR statement with no effect
+    let mut x = 0;
+    || x += 5; //~ERROR statement with no effect
 
     // Do not warn
     get_number();
@@ -36,4 +54,17 @@ fn main() {
     Struct { ..get_struct() };
     Enum::Tuple(get_number());
     Enum::Struct { field: get_number() };
+    5 + get_number();
+    *&get_number();
+    &get_number();
+    (5, 6, get_number());
+    box get_number();
+    get_number()..;
+    ..get_number();
+    5..get_number();
+    [42, get_number()];
+    [42, 55][get_number() as usize];
+    (42, get_number()).1;
+    [get_number(); 55];
+    [42; 55][get_number() as usize];
 }