New upstream version 1.23.0+dfsg1

[rustc.git] / src / tools / clippy / clippy_lints / src / no_effect.rs

diff --git a/src/tools/clippy/clippy_lints/src/no_effect.rs b/src/tools/clippy/clippy_lints/src/no_effect.rs
index 971309adb33070fdd1d732ecf07a3eef3c2c1760..a1139ff746479bd32eb661cec821885ac7a37eb5 100644 (file)
--- a/src/tools/clippy/clippy_lints/src/no_effect.rs
+++ b/src/tools/clippy/clippy_lints/src/no_effect.rs
@@ -1,7 +1,7 @@
 use rustc::lint::{LateContext, LateLintPass, LintArray, LintPass};
 use rustc::hir::def::Def;
-use rustc::hir::{Expr, Expr_, Stmt, StmtSemi, BlockCheckMode, UnsafeSource, BiAnd, BiOr};
-use utils::{in_macro, span_lint, snippet_opt, span_lint_and_sugg};
+use rustc::hir::{BiAnd, BiOr, BlockCheckMode, Expr, Expr_, Stmt, StmtSemi, UnsafeSource};
+use utils::{has_drop, in_macro, snippet_opt, span_lint, span_lint_and_sugg};
 use std::ops::Deref;
 
 /// **What it does:** Checks for statements which have no effect.
@@ -45,13 +45,12 @@ fn has_no_effect(cx: &LateContext, expr: &Expr) -> bool {
         return false;
     }
     match expr.node {
-        Expr_::ExprLit(..) |
-        Expr_::ExprClosure(.., _) |
-        Expr_::ExprPath(..) => true,
-        Expr_::ExprIndex(ref a, ref b) |
-        Expr_::ExprBinary(_, ref a, ref b) => has_no_effect(cx, a) && has_no_effect(cx, b),
-        Expr_::ExprArray(ref v) |
-        Expr_::ExprTup(ref v) => v.iter().all(|val| has_no_effect(cx, val)),
+        Expr_::ExprLit(..) | Expr_::ExprClosure(.., _) => true,
+        Expr_::ExprPath(..) => !has_drop(cx, expr),
+        Expr_::ExprIndex(ref a, ref b) | Expr_::ExprBinary(_, ref a, ref b) => {
+            has_no_effect(cx, a) && has_no_effect(cx, b)
+        },
+        Expr_::ExprArray(ref v) | Expr_::ExprTup(ref v) => v.iter().all(|val| has_no_effect(cx, val)),
         Expr_::ExprRepeat(ref inner, _) |
         Expr_::ExprCast(ref inner, _) |
         Expr_::ExprType(ref inner, _) |
@@ -61,33 +60,28 @@ fn has_no_effect(cx: &LateContext, expr: &Expr) -> bool {
         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,
-                }
+            !has_drop(cx, expr) && fields.iter().all(|field| has_no_effect(cx, &field.expr)) && match *base {
+                Some(ref base) => has_no_effect(cx, base),
+                None => true,
+            }
         },
-        Expr_::ExprCall(ref callee, ref args) => {
-            if let Expr_::ExprPath(ref qpath) = callee.node {
-                let def = cx.tables.qpath_def(qpath, callee.hir_id);
-                match def {
-                    Def::Struct(..) |
-                    Def::Variant(..) |
-                    Def::StructCtor(..) |
-                    Def::VariantCtor(..) => args.iter().all(|arg| has_no_effect(cx, arg)),
-                    _ => false,
-                }
-            } else {
-                false
+        Expr_::ExprCall(ref callee, ref args) => if let Expr_::ExprPath(ref qpath) = callee.node {
+            let def = cx.tables.qpath_def(qpath, callee.hir_id);
+            match def {
+                Def::Struct(..) | Def::Variant(..) | Def::StructCtor(..) | Def::VariantCtor(..) => {
+                    !has_drop(cx, expr) && args.iter().all(|arg| has_no_effect(cx, arg))
+                },
+                _ => false,
             }
+        } else {
+            false
         },
         Expr_::ExprBlock(ref block) => {
-            block.stmts.is_empty() &&
-                if let Some(ref expr) = block.expr {
-                    has_no_effect(cx, expr)
-                } else {
-                    false
-                }
+            block.stmts.is_empty() && if let Some(ref expr) = block.expr {
+                has_no_effect(cx, expr)
+            } else {
+                false
+            }
         },
         _ => false,
     }
@@ -143,8 +137,7 @@ fn reduce_expression<'a>(cx: &LateContext, expr: &'a Expr) -> Option<Vec<&'a Exp
         Expr_::ExprBinary(ref binop, ref a, ref b) if binop.node != BiAnd && binop.node != BiOr => {
             Some(vec![&**a, &**b])
         },
-        Expr_::ExprArray(ref v) |
-        Expr_::ExprTup(ref v) => Some(v.iter().collect()),
+        Expr_::ExprArray(ref v) | Expr_::ExprTup(ref v) => Some(v.iter().collect()),
         Expr_::ExprRepeat(ref inner, _) |
         Expr_::ExprCast(ref inner, _) |
         Expr_::ExprType(ref inner, _) |
@@ -153,7 +146,9 @@ fn reduce_expression<'a>(cx: &LateContext, expr: &'a Expr) -> Option<Vec<&'a Exp
         Expr_::ExprTupField(ref inner, _) |
         Expr_::ExprAddrOf(_, ref inner) |
         Expr_::ExprBox(ref inner) => reduce_expression(cx, inner).or_else(|| Some(vec![inner])),
-        Expr_::ExprStruct(_, ref fields, ref base) => {
+        Expr_::ExprStruct(_, ref fields, ref base) => if has_drop(cx, expr) {
+            None
+        } else {
             Some(
                 fields
                     .iter()
@@ -163,19 +158,18 @@ fn reduce_expression<'a>(cx: &LateContext, expr: &'a Expr) -> Option<Vec<&'a Exp
                     .collect(),
             )
         },
-        Expr_::ExprCall(ref callee, ref args) => {
-            if let Expr_::ExprPath(ref qpath) = callee.node {
-                let def = cx.tables.qpath_def(qpath, callee.hir_id);
-                match def {
-                    Def::Struct(..) |
-                    Def::Variant(..) |
-                    Def::StructCtor(..) |
-                    Def::VariantCtor(..) => Some(args.iter().collect()),
-                    _ => None,
-                }
-            } else {
-                None
+        Expr_::ExprCall(ref callee, ref args) => if let Expr_::ExprPath(ref qpath) = callee.node {
+            let def = cx.tables.qpath_def(qpath, callee.hir_id);
+            match def {
+                Def::Struct(..) | Def::Variant(..) | Def::StructCtor(..) | Def::VariantCtor(..)
+                    if !has_drop(cx, expr) =>
+                {
+                    Some(args.iter().collect())
+                },
+                _ => None,
             }
+        } else {
+            None
         },
         Expr_::ExprBlock(ref block) => {
             if block.stmts.is_empty() {