Add required parentheses around method receiver

Author: samueltardieu

clippy_lints/src/needless_bool.rs

@@ -6,8 +6,8 @@ use clippy_utils::diagnostics::{span_lint, span_lint_and_sugg};
 use clippy_utils::source::snippet_with_applicability;
 use clippy_utils::sugg::Sugg;
 use clippy_utils::{
-    higher, is_block_like, is_else_clause, is_expn_of, is_parent_stmt, peel_blocks, peel_blocks_with_stmt,
-    span_extract_comment, SpanlessEq,
+    get_parent_expr, higher, is_block_like, is_else_clause, is_expn_of, is_parent_stmt, is_receiver_of_method_call,
+    peel_blocks, peel_blocks_with_stmt, span_extract_comment, SpanlessEq,
 };
 use rustc_ast::ast::LitKind;
 use rustc_errors::Applicability;
@@ -154,7 +154,10 @@ impl<'tcx> LateLintPass<'tcx> for NeedlessBool {
                     snip = snip.blockify();
                 }
 
-                if condition_needs_parentheses(cond) && is_parent_stmt(cx, e.hir_id) {
+                if (condition_needs_parentheses(cond) && is_parent_stmt(cx, e.hir_id))
+                    || is_receiver_of_method_call(cx, e)
+                    || is_as_argument(cx, e)
+                {
                     snip = snip.maybe_par();
                 }
 
@@ -442,3 +445,7 @@ fn fetch_assign<'tcx>(expr: &'tcx Expr<'tcx>) -> Option<(&'tcx Expr<'tcx>, bool)
         None
     }
 }
+
+fn is_as_argument(cx: &LateContext<'_>, e: &Expr<'_>) -> bool {
+    matches!(get_parent_expr(cx, e).map(|e| e.kind), Some(ExprKind::Cast(_, _)))
+}

tests/ui/needless_bool/fixable.fixed

@@ -131,3 +131,15 @@ fn needless_bool_condition() -> bool {
 
     foo()
 }
+
+fn issue12846() {
+    let a = true;
+    let b = false;
+
+    // parentheses are needed here
+    let _x = (a && b).then(|| todo!());
+    let _x = (a && b) as u8;
+
+    // parentheses are not needed here
+    let _x = a.then(|| todo!());
+}

tests/ui/needless_bool/fixable.rs

@@ -191,3 +191,15 @@ fn needless_bool_condition() -> bool {
 
     foo()
 }
+
+fn issue12846() {
+    let a = true;
+    let b = false;
+
+    // parentheses are needed here
+    let _x = if a && b { true } else { false }.then(|| todo!());
+    let _x = if a && b { true } else { false } as u8;
+
+    // parentheses are not needed here
+    let _x = if a { true } else { false }.then(|| todo!());
+}

tests/ui/needless_bool/fixable.stderr

@@ -191,5 +191,23 @@ error: this if-then-else expression returns a bool literal
 LL |         if unsafe { no(4) } & 1 != 0 { true } else { false }
    |         ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: you can reduce it to: `(unsafe { no(4) } & 1 != 0)`
 
-error: aborting due to 21 previous errors
+error: this if-then-else expression returns a bool literal
+  --> tests/ui/needless_bool/fixable.rs:200:14
+   |
+LL |     let _x = if a && b { true } else { false }.then(|| todo!());
+   |              ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: you can reduce it to: `(a && b)`
+
+error: this if-then-else expression returns a bool literal
+  --> tests/ui/needless_bool/fixable.rs:201:14
+   |
+LL |     let _x = if a && b { true } else { false } as u8;
+   |              ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: you can reduce it to: `(a && b)`
+
+error: this if-then-else expression returns a bool literal
+  --> tests/ui/needless_bool/fixable.rs:204:14
+   |
+LL |     let _x = if a { true } else { false }.then(|| todo!());
+   |              ^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: you can reduce it to: `a`
+
+error: aborting due to 24 previous errors