Ignore tuples

Author: Henri Lunnikivi

clippy_lints/src/field_reassign_with_default.rs

@@ -4,7 +4,7 @@ use rustc_hir::def::Res;
 use rustc_data_structures::fx::FxHashMap;
 use rustc_hir::{Block, Expr, ExprKind, PatKind, QPath, Stmt, StmtKind};
 use rustc_span::symbol::{Ident, Symbol};
-use rustc_middle::ty::{Adt, TyS};
+use rustc_middle::ty::{self, Adt, TyS};
 
 use rustc_lint::{LateContext, LateLintPass};
 use rustc_session::{declare_lint_pass, declare_tool_lint};
@@ -123,7 +123,7 @@ impl LateLintPass<'_> for FieldReassignWithDefault {
     }
 }
 
-/// Returns the block indices, identifiers and types of bindings set as `Default::default()`.
+/// Returns the block indices, identifiers and types of bindings set as `Default::default()`, except for when the pattern type is a tuple.
 fn enumerate_bindings_using_default<'cx, 'hir>(cx: &LateContext<'cx>, block: &Block<'hir>) -> Vec<(usize, Symbol, &'cx TyS<'cx>)> {
     block
         .stmts
@@ -145,6 +145,10 @@ fn enumerate_bindings_using_default<'cx, 'hir>(cx: &LateContext<'cx>, block: &Bl
                 then {
                     // Get the type of the pattern
                     let ty = cx.typeck_results().pat_ty(local.pat);
+                    // Ignore tuples
+                    if let ty::Tuple(_) = ty.kind() {
+                        return None;
+                    }
                     Some((idx, ident.name, ty))
                 }
                 else {

tests/ui/field_reassign_with_default.rs

@@ -66,4 +66,10 @@ fn main() {
     // wrong, produces fourth error in stderr
     let mut a = A::default();
     a.i = 42;
+
+    // wrong, but does not produce an error in stderr, because we can't produce a correct kind of
+    // suggestion with current implementation
+    let mut c: (i32, i32) = Default::default();
+    c.0 = 42;
+    c.1 = 21;
 }