diff --git a/CHANGELOG.md b/CHANGELOG.md index 6b63dbb7eff..36b54416a19 100644 --- a/CHANGELOG.md +++ b/CHANGELOG.md @@ -1714,6 +1714,7 @@ Released 2018-09-13 [`extend_from_slice`]: https://rust-lang.github.io/rust-clippy/master/index.html#extend_from_slice [`extra_unused_lifetimes`]: https://rust-lang.github.io/rust-clippy/master/index.html#extra_unused_lifetimes [`fallible_impl_from`]: https://rust-lang.github.io/rust-clippy/master/index.html#fallible_impl_from +[`field_reassign_with_default`]: https://rust-lang.github.io/rust-clippy/master/index.html#field_reassign_with_default [`filetype_is_file`]: https://rust-lang.github.io/rust-clippy/master/index.html#filetype_is_file [`filter_map`]: https://rust-lang.github.io/rust-clippy/master/index.html#filter_map [`filter_map_next`]: https://rust-lang.github.io/rust-clippy/master/index.html#filter_map_next diff --git a/clippy_lints/src/default.rs b/clippy_lints/src/default.rs new file mode 100644 index 00000000000..612c5355338 --- /dev/null +++ b/clippy_lints/src/default.rs @@ -0,0 +1,304 @@ +use crate::utils::{any_parent_is_automatically_derived, contains_name, match_def_path, paths, qpath_res, snippet}; +use crate::utils::{span_lint_and_note, span_lint_and_sugg}; +use if_chain::if_chain; +use rustc_data_structures::fx::FxHashSet; +use rustc_errors::Applicability; +use rustc_hir::def::Res; +use rustc_hir::{Block, Expr, ExprKind, PatKind, QPath, Stmt, StmtKind}; +use rustc_lint::{LateContext, LateLintPass}; +use rustc_middle::ty::{self, Adt, Ty}; +use rustc_session::{declare_tool_lint, impl_lint_pass}; +use rustc_span::symbol::{Ident, Symbol}; +use rustc_span::Span; + +declare_clippy_lint! { + /// **What it does:** Checks for literal calls to `Default::default()`. + /// + /// **Why is this bad?** It's more clear to the reader to use the name of the type whose default is + /// being gotten than the generic `Default`. + /// + /// **Known problems:** None. + /// + /// **Example:** + /// ```rust + /// // Bad + /// let s: String = Default::default(); + /// + /// // Good + /// let s = String::default(); + /// ``` + pub DEFAULT_TRAIT_ACCESS, + pedantic, + "checks for literal calls to `Default::default()`" +} + +declare_clippy_lint! { + /// **What it does:** Checks for immediate reassignment of fields initialized + /// with Default::default(). + /// + /// **Why is this bad?**It's more idiomatic to use the [functional update syntax](https://doc.rust-lang.org/reference/expressions/struct-expr.html#functional-update-syntax). + /// + /// **Known problems:** Assignments to patterns that are of tuple type are not linted. + /// + /// **Example:** + /// Bad: + /// ``` + /// # #[derive(Default)] + /// # struct A { i: i32 } + /// let mut a: A = Default::default(); + /// a.i = 42; + /// ``` + /// Use instead: + /// ``` + /// # #[derive(Default)] + /// # struct A { i: i32 } + /// let a = A { + /// i: 42, + /// .. Default::default() + /// }; + /// ``` + pub FIELD_REASSIGN_WITH_DEFAULT, + style, + "binding initialized with Default should have its fields set in the initializer" +} + +#[derive(Default)] +pub struct Default { + // Spans linted by `field_reassign_with_default`. + reassigned_linted: FxHashSet, +} + +impl_lint_pass!(Default => [DEFAULT_TRAIT_ACCESS, FIELD_REASSIGN_WITH_DEFAULT]); + +impl LateLintPass<'_> for Default { + fn check_expr(&mut self, cx: &LateContext<'tcx>, expr: &'tcx Expr<'_>) { + if_chain! { + // Avoid cases already linted by `field_reassign_with_default` + if !self.reassigned_linted.contains(&expr.span); + if let ExprKind::Call(ref path, ..) = expr.kind; + if !any_parent_is_automatically_derived(cx.tcx, expr.hir_id); + if let ExprKind::Path(ref qpath) = path.kind; + if let Some(def_id) = cx.qpath_res(qpath, path.hir_id).opt_def_id(); + if match_def_path(cx, def_id, &paths::DEFAULT_TRAIT_METHOD); + // Detect and ignore ::default() because these calls do explicitly name the type. + if let QPath::Resolved(None, _path) = qpath; + then { + let expr_ty = cx.typeck_results().expr_ty(expr); + if let ty::Adt(def, ..) = expr_ty.kind() { + // TODO: Work out a way to put "whatever the imported way of referencing + // this type in this file" rather than a fully-qualified type. + let replacement = format!("{}::default()", cx.tcx.def_path_str(def.did)); + span_lint_and_sugg( + cx, + DEFAULT_TRAIT_ACCESS, + expr.span, + &format!("calling `{}` is more clear than this expression", replacement), + "try", + replacement, + Applicability::Unspecified, // First resolve the TODO above + ); + } + } + } + } + + fn check_block<'tcx>(&mut self, cx: &LateContext<'tcx>, block: &Block<'tcx>) { + // find all binding statements like `let mut _ = T::default()` where `T::default()` is the + // `default` method of the `Default` trait, and store statement index in current block being + // checked and the name of the bound variable + let binding_statements_using_default = enumerate_bindings_using_default(cx, block); + + // start from the `let mut _ = _::default();` and look at all the following + // statements, see if they re-assign the fields of the binding + for (stmt_idx, binding_name, binding_type, span) in binding_statements_using_default { + // the last statement of a block cannot trigger the lint + if stmt_idx == block.stmts.len() - 1 { + break; + } + + // find all "later statement"'s where the fields of the binding set as + // Default::default() get reassigned, unless the reassignment refers to the original binding + let mut first_assign = None; + let mut assigned_fields = Vec::new(); + let mut cancel_lint = false; + for consecutive_statement in &block.stmts[stmt_idx + 1..] { + // interrupt if the statement is a let binding (`Local`) that shadows the original + // binding + if stmt_shadows_binding(consecutive_statement, binding_name) { + break; + } + // find out if and which field was set by this `consecutive_statement` + else if let Some((field_ident, assign_rhs)) = + field_reassigned_by_stmt(consecutive_statement, binding_name) + { + // interrupt and cancel lint if assign_rhs references the original binding + if contains_name(binding_name, assign_rhs) { + cancel_lint = true; + break; + } + + // if the field was previously assigned, replace the assignment, otherwise insert the assignment + if let Some(prev) = assigned_fields + .iter_mut() + .find(|(field_name, _)| field_name == &field_ident.name) + { + *prev = (field_ident.name, assign_rhs); + } else { + assigned_fields.push((field_ident.name, assign_rhs)); + } + + // also set first instance of error for help message + if first_assign.is_none() { + first_assign = Some(consecutive_statement); + } + } + // interrupt also if no field was assigned, since we only want to look at consecutive statements + else { + break; + } + } + + // if there are incorrectly assigned fields, do a span_lint_and_note to suggest + // construction using `Ty { fields, ..Default::default() }` + if !assigned_fields.is_empty() && !cancel_lint { + // take the original assignment as span + let stmt = &block.stmts[stmt_idx]; + + if let StmtKind::Local(preceding_local) = &stmt.kind { + // filter out fields like `= Default::default()`, because the FRU already covers them + let assigned_fields = assigned_fields + .into_iter() + .filter(|(_, rhs)| !is_expr_default(rhs, cx)) + .collect::)>>(); + + // if all fields of the struct are not assigned, add `.. Default::default()` to the suggestion. + let ext_with_default = !fields_of_type(binding_type) + .iter() + .all(|field| assigned_fields.iter().any(|(a, _)| a == &field.name)); + + let field_list = assigned_fields + .into_iter() + .map(|(field, rhs)| { + // extract and store the assigned value for help message + let value_snippet = snippet(cx, rhs.span, ".."); + format!("{}: {}", field, value_snippet) + }) + .collect::>() + .join(", "); + + let sugg = if ext_with_default { + if field_list.is_empty() { + format!("{}::default()", binding_type) + } else { + format!("{} {{ {}, ..Default::default() }}", binding_type, field_list) + } + } else { + format!("{} {{ {} }}", binding_type, field_list) + }; + + // span lint once per statement that binds default + span_lint_and_note( + cx, + FIELD_REASSIGN_WITH_DEFAULT, + first_assign.unwrap().span, + "field assignment outside of initializer for an instance created with Default::default()", + Some(preceding_local.span), + &format!( + "consider initializing the variable with `{}` and removing relevant reassignments", + sugg + ), + ); + self.reassigned_linted.insert(span); + } + } + } + } +} + +/// Checks if the given expression is the `default` method belonging to the `Default` trait. +fn is_expr_default<'tcx>(expr: &'tcx Expr<'tcx>, cx: &LateContext<'tcx>) -> bool { + if_chain! { + if let ExprKind::Call(ref fn_expr, _) = &expr.kind; + if let ExprKind::Path(qpath) = &fn_expr.kind; + if let Res::Def(_, def_id) = qpath_res(cx, qpath, fn_expr.hir_id); + then { + // right hand side of assignment is `Default::default` + match_def_path(cx, def_id, &paths::DEFAULT_TRAIT_METHOD) + } else { + false + } + } +} + +/// 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<'tcx>( + cx: &LateContext<'tcx>, + block: &Block<'tcx>, +) -> Vec<(usize, Symbol, Ty<'tcx>, Span)> { + block + .stmts + .iter() + .enumerate() + .filter_map(|(idx, stmt)| { + if_chain! { + // only take `let ...` statements + if let StmtKind::Local(ref local) = stmt.kind; + // only take bindings to identifiers + if let PatKind::Binding(_, _, ident, _) = local.pat.kind; + // that are not tuples + let ty = cx.typeck_results().pat_ty(local.pat); + if !matches!(ty.kind(), ty::Tuple(_)); + // only when assigning `... = Default::default()` + if let Some(ref expr) = local.init; + if is_expr_default(expr, cx); + then { + Some((idx, ident.name, ty, expr.span)) + } else { + None + } + } + }) + .collect() +} + +fn stmt_shadows_binding(this: &Stmt<'_>, shadowed: Symbol) -> bool { + if let StmtKind::Local(local) = &this.kind { + if let PatKind::Binding(_, _, ident, _) = local.pat.kind { + return ident.name == shadowed; + } + } + false +} + +/// Returns the reassigned field and the assigning expression (right-hand side of assign). +fn field_reassigned_by_stmt<'tcx>(this: &Stmt<'tcx>, binding_name: Symbol) -> Option<(Ident, &'tcx Expr<'tcx>)> { + if_chain! { + // only take assignments + if let StmtKind::Semi(ref later_expr) = this.kind; + if let ExprKind::Assign(ref assign_lhs, ref assign_rhs, _) = later_expr.kind; + // only take assignments to fields where the left-hand side field is a field of + // the same binding as the previous statement + if let ExprKind::Field(ref binding, field_ident) = assign_lhs.kind; + if let ExprKind::Path(ref qpath) = binding.kind; + if let QPath::Resolved(_, path) = qpath; + if let Some(second_binding_name) = path.segments.last(); + if second_binding_name.ident.name == binding_name; + then { + Some((field_ident, assign_rhs)) + } else { + None + } + } +} + +/// Returns the vec of fields for a struct and an empty vec for non-struct ADTs. +fn fields_of_type(ty: Ty<'_>) -> Vec { + if let Adt(adt, _) = ty.kind() { + if adt.is_struct() { + let variant = &adt.non_enum_variant(); + return variant.fields.iter().map(|f| f.ident).collect(); + } + } + vec![] +} diff --git a/clippy_lints/src/default_trait_access.rs b/clippy_lints/src/default_trait_access.rs deleted file mode 100644 index 3048436d9a7..00000000000 --- a/clippy_lints/src/default_trait_access.rs +++ /dev/null @@ -1,62 +0,0 @@ -use if_chain::if_chain; -use rustc_errors::Applicability; -use rustc_hir::{Expr, ExprKind, QPath}; -use rustc_lint::{LateContext, LateLintPass}; -use rustc_middle::ty; -use rustc_session::{declare_lint_pass, declare_tool_lint}; - -use crate::utils::{any_parent_is_automatically_derived, match_def_path, paths, span_lint_and_sugg}; - -declare_clippy_lint! { - /// **What it does:** Checks for literal calls to `Default::default()`. - /// - /// **Why is this bad?** It's more clear to the reader to use the name of the type whose default is - /// being gotten than the generic `Default`. - /// - /// **Known problems:** None. - /// - /// **Example:** - /// ```rust - /// // Bad - /// let s: String = Default::default(); - /// - /// // Good - /// let s = String::default(); - /// ``` - pub DEFAULT_TRAIT_ACCESS, - pedantic, - "checks for literal calls to `Default::default()`" -} - -declare_lint_pass!(DefaultTraitAccess => [DEFAULT_TRAIT_ACCESS]); - -impl<'tcx> LateLintPass<'tcx> for DefaultTraitAccess { - fn check_expr(&mut self, cx: &LateContext<'tcx>, expr: &'tcx Expr<'_>) { - if_chain! { - if let ExprKind::Call(ref path, ..) = expr.kind; - if !any_parent_is_automatically_derived(cx.tcx, expr.hir_id); - if let ExprKind::Path(ref qpath) = path.kind; - if let Some(def_id) = cx.qpath_res(qpath, path.hir_id).opt_def_id(); - if match_def_path(cx, def_id, &paths::DEFAULT_TRAIT_METHOD); - // Detect and ignore ::default() because these calls do explicitly name the type. - if let QPath::Resolved(None, _path) = qpath; - then { - let expr_ty = cx.typeck_results().expr_ty(expr); - if let ty::Adt(def, ..) = expr_ty.kind() { - // TODO: Work out a way to put "whatever the imported way of referencing - // this type in this file" rather than a fully-qualified type. - let replacement = format!("{}::default()", cx.tcx.def_path_str(def.did)); - span_lint_and_sugg( - cx, - DEFAULT_TRAIT_ACCESS, - expr.span, - &format!("calling `{}` is more clear than this expression", replacement), - "try", - replacement, - Applicability::Unspecified, // First resolve the TODO above - ); - } - } - } - } -} diff --git a/clippy_lints/src/lib.rs b/clippy_lints/src/lib.rs index 5c3af014ee1..bb94b3f6cbe 100644 --- a/clippy_lints/src/lib.rs +++ b/clippy_lints/src/lib.rs @@ -176,7 +176,7 @@ macro_rules! declare_clippy_lint { mod copy_iterator; mod create_dir; mod dbg_macro; -mod default_trait_access; +mod default; mod dereference; mod derive; mod disallowed_method; @@ -537,7 +537,8 @@ pub fn register_plugins(store: &mut rustc_lint::LintStore, sess: &Session, conf: ©_iterator::COPY_ITERATOR, &create_dir::CREATE_DIR, &dbg_macro::DBG_MACRO, - &default_trait_access::DEFAULT_TRAIT_ACCESS, + &default::DEFAULT_TRAIT_ACCESS, + &default::FIELD_REASSIGN_WITH_DEFAULT, &dereference::EXPLICIT_DEREF_METHODS, &derive::DERIVE_HASH_XOR_EQ, &derive::DERIVE_ORD_XOR_PARTIAL_ORD, @@ -1049,7 +1050,6 @@ pub fn register_plugins(store: &mut rustc_lint::LintStore, sess: &Session, conf: store.register_late_pass(|| box neg_cmp_op_on_partial_ord::NoNegCompOpForPartialOrd); store.register_late_pass(|| box unwrap::Unwrap); store.register_late_pass(|| box duration_subsec::DurationSubsec); - store.register_late_pass(|| box default_trait_access::DefaultTraitAccess); store.register_late_pass(|| box indexing_slicing::IndexingSlicing); store.register_late_pass(|| box non_copy_const::NonCopyConst); store.register_late_pass(|| box ptr_offset_with_cast::PtrOffsetWithCast); @@ -1100,6 +1100,7 @@ pub fn register_plugins(store: &mut rustc_lint::LintStore, sess: &Session, conf: let enum_variant_name_threshold = conf.enum_variant_name_threshold; store.register_early_pass(move || box enum_variants::EnumVariantNames::new(enum_variant_name_threshold)); store.register_early_pass(|| box tabs_in_doc_comments::TabsInDocComments); + store.register_late_pass(|| box default::Default::default()); store.register_late_pass(|| box unused_self::UnusedSelf); store.register_late_pass(|| box mutable_debug_assertion::DebugAssertWithMutCall); store.register_late_pass(|| box exit::Exit); @@ -1212,7 +1213,7 @@ pub fn register_plugins(store: &mut rustc_lint::LintStore, sess: &Session, conf: LintId::of(&checked_conversions::CHECKED_CONVERSIONS), LintId::of(&copies::SAME_FUNCTIONS_IN_IF_CONDITION), LintId::of(©_iterator::COPY_ITERATOR), - LintId::of(&default_trait_access::DEFAULT_TRAIT_ACCESS), + LintId::of(&default::DEFAULT_TRAIT_ACCESS), LintId::of(&dereference::EXPLICIT_DEREF_METHODS), LintId::of(&derive::EXPL_IMPL_CLONE_ON_COPY), LintId::of(&derive::UNSAFE_DERIVE_DESERIALIZE), @@ -1321,6 +1322,7 @@ pub fn register_plugins(store: &mut rustc_lint::LintStore, sess: &Session, conf: LintId::of(&comparison_chain::COMPARISON_CHAIN), LintId::of(&copies::IFS_SAME_COND), LintId::of(&copies::IF_SAME_THEN_ELSE), + LintId::of(&default::FIELD_REASSIGN_WITH_DEFAULT), LintId::of(&derive::DERIVE_HASH_XOR_EQ), LintId::of(&derive::DERIVE_ORD_XOR_PARTIAL_ORD), LintId::of(&doc::MISSING_SAFETY_DOC), @@ -1581,6 +1583,7 @@ pub fn register_plugins(store: &mut rustc_lint::LintStore, sess: &Session, conf: LintId::of(&blocks_in_if_conditions::BLOCKS_IN_IF_CONDITIONS), LintId::of(&collapsible_if::COLLAPSIBLE_IF), LintId::of(&comparison_chain::COMPARISON_CHAIN), + LintId::of(&default::FIELD_REASSIGN_WITH_DEFAULT), LintId::of(&doc::MISSING_SAFETY_DOC), LintId::of(&doc::NEEDLESS_DOCTEST_MAIN), LintId::of(&enum_variants::ENUM_VARIANT_NAMES), diff --git a/src/lintlist/mod.rs b/src/lintlist/mod.rs index 016bda77ef5..a3645a65182 100644 --- a/src/lintlist/mod.rs +++ b/src/lintlist/mod.rs @@ -359,7 +359,7 @@ group: "pedantic", desc: "checks for literal calls to `Default::default()`", deprecation: None, - module: "default_trait_access", + module: "default", }, Lint { name: "deprecated_cfg_attr", @@ -627,6 +627,13 @@ deprecation: None, module: "fallible_impl_from", }, + Lint { + name: "field_reassign_with_default", + group: "style", + desc: "binding initialized with Default should have its fields set in the initializer", + deprecation: None, + module: "default", + }, Lint { name: "filetype_is_file", group: "restriction", diff --git a/tests/ui/field_reassign_with_default.rs b/tests/ui/field_reassign_with_default.rs new file mode 100644 index 00000000000..79a30c22f95 --- /dev/null +++ b/tests/ui/field_reassign_with_default.rs @@ -0,0 +1,110 @@ +#![warn(clippy::field_reassign_with_default)] + +#[derive(Default)] +struct A { + i: i32, + j: i64, +} + +struct B { + i: i32, + j: i64, +} + +/// Implements .next() that returns a different number each time. +struct SideEffect(i32); + +impl SideEffect { + fn new() -> SideEffect { + SideEffect(0) + } + fn next(&mut self) -> i32 { + self.0 += 1; + self.0 + } +} + +fn main() { + // wrong, produces first error in stderr + let mut a: A = Default::default(); + a.i = 42; + + // right + let mut a: A = Default::default(); + + // right + let a = A { + i: 42, + ..Default::default() + }; + + // right + let mut a: A = Default::default(); + if a.i == 0 { + a.j = 12; + } + + // right + let mut a: A = Default::default(); + let b = 5; + + // right + let mut b = 32; + let mut a: A = Default::default(); + b = 2; + + // right + let b: B = B { i: 42, j: 24 }; + + // right + let mut b: B = B { i: 42, j: 24 }; + b.i = 52; + + // right + let mut b = B { i: 15, j: 16 }; + let mut a: A = Default::default(); + b.i = 2; + + // wrong, produces second error in stderr + let mut a: A = Default::default(); + a.j = 43; + a.i = 42; + + // wrong, produces third error in stderr + let mut a: A = Default::default(); + a.i = 42; + a.j = 43; + a.j = 44; + + // 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; + + // wrong, produces the fifth error in stderr + let mut a: A = Default::default(); + a.i = Default::default(); + + // wrong, produces the sixth error in stderr + let mut a: A = Default::default(); + a.i = Default::default(); + a.j = 45; + + // right, because an assignment refers to another field + let mut x = A::default(); + x.i = 42; + x.j = 21 + x.i as i64; + + // right, we bail out if there's a reassignment to the same variable, since there is a risk of + // side-effects affecting the outcome + let mut x = A::default(); + let mut side_effect = SideEffect::new(); + x.i = side_effect.next(); + x.j = 2; + x.i = side_effect.next(); +} diff --git a/tests/ui/field_reassign_with_default.stderr b/tests/ui/field_reassign_with_default.stderr new file mode 100644 index 00000000000..c788ebae552 --- /dev/null +++ b/tests/ui/field_reassign_with_default.stderr @@ -0,0 +1,75 @@ +error: field assignment outside of initializer for an instance created with Default::default() + --> $DIR/field_reassign_with_default.rs:30:5 + | +LL | a.i = 42; + | ^^^^^^^^^ + | + = note: `-D clippy::field-reassign-with-default` implied by `-D warnings` +note: consider initializing the variable with `A { i: 42, ..Default::default() }` and removing relevant reassignments + --> $DIR/field_reassign_with_default.rs:29:5 + | +LL | let mut a: A = Default::default(); + | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ + +error: field assignment outside of initializer for an instance created with Default::default() + --> $DIR/field_reassign_with_default.rs:70:5 + | +LL | a.j = 43; + | ^^^^^^^^^ + | +note: consider initializing the variable with `A { j: 43, i: 42 }` and removing relevant reassignments + --> $DIR/field_reassign_with_default.rs:69:5 + | +LL | let mut a: A = Default::default(); + | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ + +error: field assignment outside of initializer for an instance created with Default::default() + --> $DIR/field_reassign_with_default.rs:75:5 + | +LL | a.i = 42; + | ^^^^^^^^^ + | +note: consider initializing the variable with `A { i: 42, j: 44 }` and removing relevant reassignments + --> $DIR/field_reassign_with_default.rs:74:5 + | +LL | let mut a: A = Default::default(); + | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ + +error: field assignment outside of initializer for an instance created with Default::default() + --> $DIR/field_reassign_with_default.rs:81:5 + | +LL | a.i = 42; + | ^^^^^^^^^ + | +note: consider initializing the variable with `A { i: 42, ..Default::default() }` and removing relevant reassignments + --> $DIR/field_reassign_with_default.rs:80:5 + | +LL | let mut a = A::default(); + | ^^^^^^^^^^^^^^^^^^^^^^^^^ + +error: field assignment outside of initializer for an instance created with Default::default() + --> $DIR/field_reassign_with_default.rs:91:5 + | +LL | a.i = Default::default(); + | ^^^^^^^^^^^^^^^^^^^^^^^^^ + | +note: consider initializing the variable with `A::default()` and removing relevant reassignments + --> $DIR/field_reassign_with_default.rs:90:5 + | +LL | let mut a: A = Default::default(); + | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ + +error: field assignment outside of initializer for an instance created with Default::default() + --> $DIR/field_reassign_with_default.rs:95:5 + | +LL | a.i = Default::default(); + | ^^^^^^^^^^^^^^^^^^^^^^^^^ + | +note: consider initializing the variable with `A { j: 45, ..Default::default() }` and removing relevant reassignments + --> $DIR/field_reassign_with_default.rs:94:5 + | +LL | let mut a: A = Default::default(); + | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ + +error: aborting due to 6 previous errors +