Don't lint unnecessary_operation in mixed macro contexts

Author: Jarcho

clippy_lints/src/no_effect.rs

@@ -6,7 +6,8 @@ use clippy_utils::ty::has_drop;
 use rustc_errors::Applicability;
 use rustc_hir::def::{DefKind, Res};
 use rustc_hir::{is_range_literal, BinOpKind, BlockCheckMode, Expr, ExprKind, PatKind, Stmt, StmtKind, UnsafeSource};
-use rustc_lint::{LateContext, LateLintPass};
+use rustc_lint::{LateContext, LateLintPass, LintContext};
+use rustc_middle::lint::in_external_macro;
 use rustc_session::{declare_lint_pass, declare_tool_lint};
 use std::ops::Deref;
 
@@ -159,8 +160,11 @@ fn has_no_effect(cx: &LateContext<'_>, expr: &Expr<'_>) -> bool {
 fn check_unnecessary_operation(cx: &LateContext<'_>, stmt: &Stmt<'_>) {
     if_chain! {
         if let StmtKind::Semi(expr) = stmt.kind;
+        let ctxt = stmt.span.ctxt();
+        if expr.span.ctxt() == ctxt;
         if let Some(reduced) = reduce_expression(cx, expr);
-        if !&reduced.iter().any(|e| e.span.from_expansion());
+        if !in_external_macro(cx.sess(), stmt.span);
+        if reduced.iter().all(|e| e.span.ctxt() == ctxt);
         then {
             if let ExprKind::Index(..) = &expr.kind {
                 let snippet = if let (Some(arr), Some(func)) =

tests/ui/unnecessary_operation.fixed

@@ -76,4 +76,13 @@ fn main() {
     DropStruct { ..get_drop_struct() };
     DropEnum::Tuple(get_number());
     DropEnum::Struct { field: get_number() };
+
+    // Issue #9954
+    fn one() -> i8 {
+        1
+    }
+    macro_rules! use_expr {
+        ($($e:expr),*) => {{ $($e;)* }}
+    }
+    use_expr!(isize::MIN / -(one() as isize), i8::MIN / -one());
 }

tests/ui/unnecessary_operation.rs

@@ -80,4 +80,13 @@ fn main() {
     DropStruct { ..get_drop_struct() };
     DropEnum::Tuple(get_number());
     DropEnum::Struct { field: get_number() };
+
+    // Issue #9954
+    fn one() -> i8 {
+        1
+    }
+    macro_rules! use_expr {
+        ($($e:expr),*) => {{ $($e;)* }}
+    }
+    use_expr!(isize::MIN / -(one() as isize), i8::MIN / -one());
 }