Auto merge of #46980 - zackmdavis:and_the_case_of_the_needlessly_parenthesized_arguments, r=petrochenkov

in which the unused-parens lint comes to cover function and method args

Resolves #46137.

Author: bors

src/liballoc/vec_deque.rs

@@ -2480,7 +2480,7 @@ impl<T> From<VecDeque<T>> for Vec<T> {
             if other.is_contiguous() {
                 ptr::copy(buf.offset(tail as isize), buf, len);
             } else {
-                if (tail - head) >= cmp::min((cap - tail), head) {
+                if (tail - head) >= cmp::min(cap - tail, head) {
                     // There is enough free space in the centre for the shortest block so we can
                     // do this in at most three copy moves.
                     if (cap - tail) > head {

src/librustc_lint/unused.rs

@@ -302,6 +302,18 @@ impl EarlyLintPass for UnusedParens {
             Assign(_, ref value) => (value, "assigned value", false),
             AssignOp(.., ref value) => (value, "assigned value", false),
             InPlace(_, ref value) => (value, "emplacement value", false),
+            Call(_, ref args) => {
+                for arg in args {
+                    self.check_unused_parens_core(cx, arg, "function argument", false)
+                }
+                return;
+            },
+            MethodCall(_, ref args) => {
+                for arg in &args[1..] { // first "argument" is self (which sometimes needs parens)
+                    self.check_unused_parens_core(cx, arg, "method argument", false)
+                }
+                return;
+            }
             _ => return,
         };
         self.check_unused_parens_core(cx, &value, msg, struct_lit_needs_parens);

src/test/compile-fail/lint-unnecessary-parens.rs

@@ -13,19 +13,19 @@
 #[derive(Eq, PartialEq)]
 struct X { y: bool }
 impl X {
-    fn foo(&self) -> bool { self.y }
+    fn foo(&self, conjunct: bool) -> bool { self.y && conjunct }
 }
 
 fn foo() -> isize {
     return (1); //~ ERROR unnecessary parentheses around `return` value
 }
-fn bar() -> X {
-    return (X { y: true }); //~ ERROR unnecessary parentheses around `return` value
+fn bar(y: bool) -> X {
+    return (X { y }); //~ ERROR unnecessary parentheses around `return` value
 }
 
 fn main() {
     foo();
-    bar();
+    bar((true)); //~ ERROR unnecessary parentheses around function argument
 
     if (true) {} //~ ERROR unnecessary parentheses around `if` condition
     while (true) {} //~ ERROR unnecessary parentheses around `while` condition
@@ -40,13 +40,15 @@ fn main() {
     if (X { y: true } == v) {}
     if (X { y: false }.y) {}
 
-    while (X { y: false }.foo()) {}
+    while (X { y: false }.foo(true)) {}
     while (true | X { y: false }.y) {}
 
     match (X { y: false }) {
         _ => {}
     }
 
+    X { y: false }.foo((true)); //~ ERROR unnecessary parentheses around method argument
+
     let mut _a = (0); //~ ERROR unnecessary parentheses around assigned value
     _a = (0); //~ ERROR unnecessary parentheses around assigned value
     _a += (1); //~ ERROR unnecessary parentheses around assigned value