From 22f8c13cf5650d6c9d6ee7b4f0e88bffba9076ca Mon Sep 17 00:00:00 2001 From: Jason Newcomb Date: Thu, 1 Apr 2021 22:46:10 -0400 Subject: [PATCH] Improve `implicit_return` Better suggestions when returning macro calls. Suggest changeing all the break expressions in a loop, not just the final statement. Don't lint divergent functions. Don't suggest returning the result of any divergent fuction. --- clippy_lints/src/implicit_return.rs | 241 ++++++++++++++++++---------- clippy_utils/src/source.rs | 31 ++-- clippy_utils/src/visitors.rs | 55 ++++++- tests/ui/implicit_return.fixed | 62 +++++-- tests/ui/implicit_return.rs | 62 +++++-- tests/ui/implicit_return.stderr | 55 +++++-- 6 files changed, 366 insertions(+), 140 deletions(-) diff --git a/clippy_lints/src/implicit_return.rs b/clippy_lints/src/implicit_return.rs index 6b379b0d59b..251a7361871 100644 --- a/clippy_lints/src/implicit_return.rs +++ b/clippy_lints/src/implicit_return.rs @@ -1,13 +1,15 @@ -use clippy_utils::diagnostics::span_lint_and_then; -use clippy_utils::match_panic_def_id; -use clippy_utils::source::snippet_opt; -use if_chain::if_chain; +use clippy_utils::{ + diagnostics::span_lint_and_sugg, + source::{snippet_with_applicability, snippet_with_context, walk_span_to_context}, + visitors::visit_break_exprs, +}; use rustc_errors::Applicability; use rustc_hir::intravisit::FnKind; -use rustc_hir::{Body, Expr, ExprKind, FnDecl, HirId, MatchSource, StmtKind}; -use rustc_lint::{LateContext, LateLintPass}; +use rustc_hir::{Block, Body, Expr, ExprKind, FnDecl, FnRetTy, HirId}; +use rustc_lint::{LateContext, LateLintPass, LintContext}; +use rustc_middle::lint::in_external_macro; use rustc_session::{declare_lint_pass, declare_tool_lint}; -use rustc_span::source_map::Span; +use rustc_span::{Span, SyntaxContext}; declare_clippy_lint! { /// **What it does:** Checks for missing return statements at the end of a block. @@ -39,89 +41,159 @@ declare_lint_pass!(ImplicitReturn => [IMPLICIT_RETURN]); -static LINT_BREAK: &str = "change `break` to `return` as shown"; -static LINT_RETURN: &str = "add `return` as shown"; - -fn lint(cx: &LateContext<'_>, outer_span: Span, inner_span: Span, msg: &str) { - let outer_span = outer_span.source_callsite(); - let inner_span = inner_span.source_callsite(); - - span_lint_and_then(cx, IMPLICIT_RETURN, outer_span, "missing `return` statement", |diag| { - if let Some(snippet) = snippet_opt(cx, inner_span) { - diag.span_suggestion( - outer_span, - msg, - format!("return {}", snippet), - Applicability::MachineApplicable, - ); - } - }); +fn lint_return(cx: &LateContext<'_>, span: Span) { + let mut app = Applicability::MachineApplicable; + let snip = snippet_with_applicability(cx, span, "..", &mut app); + span_lint_and_sugg( + cx, + IMPLICIT_RETURN, + span, + "missing `return` statement", + "add `return` as shown", + format!("return {}", snip), + app, + ); +} + +fn lint_break(cx: &LateContext<'_>, break_span: Span, expr_span: Span) { + let mut app = Applicability::MachineApplicable; + let snip = snippet_with_context(cx, expr_span, break_span.ctxt(), "..", &mut app).0; + span_lint_and_sugg( + cx, + IMPLICIT_RETURN, + break_span, + "missing `return` statement", + "change `break` to `return` as shown", + format!("return {}", snip), + app, + ) +} + +enum LintLocation { + /// The lint was applied to a parent expression. + Parent, + /// The lint was applied to this expression, a child, or not applied. + Inner, } +impl LintLocation { + fn still_parent(self, b: bool) -> Self { + if b { self } else { Self::Inner } + } -fn expr_match(cx: &LateContext<'_>, expr: &Expr<'_>) { + fn is_parent(&self) -> bool { + matches!(*self, Self::Parent) + } +} + +// Gets the call site if the span is in a child context. Otherwise returns `None`. +fn get_call_site(span: Span, ctxt: SyntaxContext) -> Option { + (span.ctxt() != ctxt).then(|| walk_span_to_context(span, ctxt).unwrap_or(span)) +} + +fn lint_implicit_returns( + cx: &LateContext<'tcx>, + expr: &'tcx Expr<'_>, + // The context of the function body. + ctxt: SyntaxContext, + // Whether the expression is from a macro expansion. + call_site_span: Option, +) -> LintLocation { match expr.kind { - // loops could be using `break` instead of `return` - ExprKind::Block(block, ..) | ExprKind::Loop(block, ..) => { - if let Some(expr) = &block.expr { - expr_match(cx, expr); - } - // only needed in the case of `break` with `;` at the end - else if let Some(stmt) = block.stmts.last() { - if_chain! { - if let StmtKind::Semi(expr, ..) = &stmt.kind; - // make sure it's a break, otherwise we want to skip - if let ExprKind::Break(.., Some(break_expr)) = &expr.kind; - then { - lint(cx, expr.span, break_expr.span, LINT_BREAK); - } - } - } - }, - // use `return` instead of `break` - ExprKind::Break(.., break_expr) => { - if let Some(break_expr) = break_expr { - lint(cx, expr.span, break_expr.span, LINT_BREAK); + ExprKind::Block( + Block { + expr: Some(block_expr), .. + }, + _, + ) => lint_implicit_returns( + cx, + block_expr, + ctxt, + call_site_span.or_else(|| get_call_site(block_expr.span, ctxt)), + ) + .still_parent(call_site_span.is_some()), + + ExprKind::If(_, then_expr, Some(else_expr)) => { + // Both `then_expr` or `else_expr` are required to be blocks in the same context as the `if`. Don't + // bother checking. + let res = lint_implicit_returns(cx, then_expr, ctxt, call_site_span).still_parent(call_site_span.is_some()); + if res.is_parent() { + // The return was added as a parent of this if expression. + return res; } + lint_implicit_returns(cx, else_expr, ctxt, call_site_span).still_parent(call_site_span.is_some()) }, - ExprKind::If(.., if_expr, else_expr) => { - expr_match(cx, if_expr); - if let Some(else_expr) = else_expr { - expr_match(cx, else_expr); + ExprKind::Match(_, arms, _) => { + for arm in arms { + let res = lint_implicit_returns( + cx, + arm.body, + ctxt, + call_site_span.or_else(|| get_call_site(arm.body.span, ctxt)), + ) + .still_parent(call_site_span.is_some()); + if res.is_parent() { + // The return was added as a parent of this match expression. + return res; + } } + LintLocation::Inner }, - ExprKind::Match(.., arms, source) => { - let check_all_arms = match source { - MatchSource::IfLetDesugar { - contains_else_clause: has_else, - } => has_else, - _ => true, - }; - - if check_all_arms { - for arm in arms { - expr_match(cx, arm.body); + + ExprKind::Loop(block, ..) => { + let mut add_return = false; + visit_break_exprs(block, |break_expr, dest, sub_expr| { + if dest.target_id.ok() == Some(expr.hir_id) { + if call_site_span.is_none() && break_expr.span.ctxt() == ctxt { + lint_break(cx, break_expr.span, sub_expr.unwrap().span); + } else { + // the break expression is from a macro call, add a return to the loop + add_return = true; + } + } + }); + if add_return { + #[allow(clippy::option_if_let_else)] + if let Some(span) = call_site_span { + lint_return(cx, span); + LintLocation::Parent + } else { + lint_return(cx, expr.span); + LintLocation::Inner } } else { - expr_match(cx, arms.first().expect("`if let` doesn't have a single arm").body); + LintLocation::Inner } }, - // skip if it already has a return statement - ExprKind::Ret(..) => (), - // make sure it's not a call that panics - ExprKind::Call(expr, ..) => { - if_chain! { - if let ExprKind::Path(qpath) = &expr.kind; - if let Some(path_def_id) = cx.qpath_res(qpath, expr.hir_id).opt_def_id(); - if match_panic_def_id(cx, path_def_id); - then { } - else { - lint(cx, expr.span, expr.span, LINT_RETURN) - } + + // If expressions without an else clause, and blocks without a final expression can only be the final expression + // if they are divergent, or return the unit type. + ExprKind::If(_, _, None) | ExprKind::Block(Block { expr: None, .. }, _) | ExprKind::Ret(_) => { + LintLocation::Inner + }, + + // Any divergent expression doesn't need a return statement. + ExprKind::MethodCall(..) + | ExprKind::Call(..) + | ExprKind::Binary(..) + | ExprKind::Unary(..) + | ExprKind::Index(..) + if cx.typeck_results().expr_ty(expr).is_never() => + { + LintLocation::Inner + }, + + _ => + { + #[allow(clippy::option_if_let_else)] + if let Some(span) = call_site_span { + lint_return(cx, span); + LintLocation::Parent + } else { + lint_return(cx, expr.span); + LintLocation::Inner } }, - // everything else is missing `return` - _ => lint(cx, expr.span, expr.span, LINT_RETURN), } } @@ -129,19 +201,24 @@ impl<'tcx> LateLintPass<'tcx> for ImplicitReturn { fn check_fn( &mut self, cx: &LateContext<'tcx>, - _: FnKind<'tcx>, - _: &'tcx FnDecl<'_>, + kind: FnKind<'tcx>, + decl: &'tcx FnDecl<'_>, body: &'tcx Body<'_>, span: Span, _: HirId, ) { - if span.from_expansion() { + if (!matches!(kind, FnKind::Closure) && matches!(decl.output, FnRetTy::DefaultReturn(_))) + || span.ctxt() != body.value.span.ctxt() + || in_external_macro(cx.sess(), span) + { return; } - let body = cx.tcx.hir().body(body.id()); - if cx.typeck_results().expr_ty(&body.value).is_unit() { + + let res_ty = cx.typeck_results().expr_ty(&body.value); + if res_ty.is_unit() || res_ty.is_never() { return; } - expr_match(cx, &body.value); + + lint_implicit_returns(cx, &body.value, body.value.span.ctxt(), None); } } diff --git a/clippy_utils/src/source.rs b/clippy_utils/src/source.rs index 53180d1f9f5..2e731c182ec 100644 --- a/clippy_utils/src/source.rs +++ b/clippy_utils/src/source.rs @@ -280,17 +280,17 @@ pub fn snippet_with_context( default: &'a str, applicability: &mut Applicability, ) -> (Cow<'a, str>, bool) { - let outer_span = hygiene::walk_chain(span, outer); - let (span, is_macro_call) = if outer_span.ctxt() == outer { - (outer_span, span.ctxt() != outer) - } else { - // The span is from a macro argument, and the outer context is the macro using the argument - if *applicability != Applicability::Unspecified { - *applicability = Applicability::MaybeIncorrect; - } - // TODO: get the argument span. - (span, false) - }; + let (span, is_macro_call) = walk_span_to_context(span, outer).map_or_else( + || { + // The span is from a macro argument, and the outer context is the macro using the argument + if *applicability != Applicability::Unspecified { + *applicability = Applicability::MaybeIncorrect; + } + // TODO: get the argument span. + (span, false) + }, + |outer_span| (outer_span, span.ctxt() != outer), + ); ( snippet_with_applicability(cx, span, default, applicability), @@ -298,6 +298,15 @@ pub fn snippet_with_context( ) } +/// Walks the span up to the target context, thereby returning the macro call site if the span is +/// inside a macro expansion, or the original span if it is not. Note this will return `None` in the +/// case of the span being in a macro expansion, but the target context is from expanding a macro +/// argument. +pub fn walk_span_to_context(span: Span, outer: SyntaxContext) -> Option { + let outer_span = hygiene::walk_chain(span, outer); + (outer_span.ctxt() == outer).then(|| outer_span) +} + /// Removes block comments from the given `Vec` of lines. /// /// # Examples diff --git a/clippy_utils/src/visitors.rs b/clippy_utils/src/visitors.rs index 5a8c629e333..d431bdf34ee 100644 --- a/clippy_utils/src/visitors.rs +++ b/clippy_utils/src/visitors.rs @@ -1,7 +1,7 @@ use crate::path_to_local_id; use rustc_hir as hir; -use rustc_hir::intravisit::{self, walk_expr, NestedVisitorMap, Visitor}; -use rustc_hir::{Arm, Body, Expr, HirId, Stmt}; +use rustc_hir::intravisit::{self, walk_expr, ErasedMap, NestedVisitorMap, Visitor}; +use rustc_hir::{Arm, Block, Body, Destination, Expr, ExprKind, HirId, Stmt}; use rustc_lint::LateContext; use rustc_middle::hir::map::Map; @@ -188,3 +188,54 @@ fn nested_visit_map(&mut self) -> NestedVisitorMap { NestedVisitorMap::OnlyBodies(self.hir) } } + +pub trait Visitable<'tcx> { + fn visit>(self, v: &mut V); +} +impl Visitable<'tcx> for &'tcx Expr<'tcx> { + fn visit>(self, v: &mut V) { + v.visit_expr(self) + } +} +impl Visitable<'tcx> for &'tcx Block<'tcx> { + fn visit>(self, v: &mut V) { + v.visit_block(self) + } +} +impl<'tcx> Visitable<'tcx> for &'tcx Stmt<'tcx> { + fn visit>(self, v: &mut V) { + v.visit_stmt(self) + } +} +impl<'tcx> Visitable<'tcx> for &'tcx Body<'tcx> { + fn visit>(self, v: &mut V) { + v.visit_body(self) + } +} +impl<'tcx> Visitable<'tcx> for &'tcx Arm<'tcx> { + fn visit>(self, v: &mut V) { + v.visit_arm(self) + } +} + +pub fn visit_break_exprs<'tcx>( + node: impl Visitable<'tcx>, + f: impl FnMut(&'tcx Expr<'tcx>, Destination, Option<&'tcx Expr<'tcx>>), +) { + struct V(F); + impl<'tcx, F: FnMut(&'tcx Expr<'tcx>, Destination, Option<&'tcx Expr<'tcx>>)> Visitor<'tcx> for V { + type Map = ErasedMap<'tcx>; + fn nested_visit_map(&mut self) -> NestedVisitorMap { + NestedVisitorMap::None + } + + fn visit_expr(&mut self, e: &'tcx Expr<'_>) { + if let ExprKind::Break(dest, sub_expr) = e.kind { + self.0(e, dest, sub_expr) + } + walk_expr(self, e); + } + } + + node.visit(&mut V(f)); +} diff --git a/tests/ui/implicit_return.fixed b/tests/ui/implicit_return.fixed index 59f7ad9c106..c0fc4b926a0 100644 --- a/tests/ui/implicit_return.fixed +++ b/tests/ui/implicit_return.fixed @@ -1,7 +1,7 @@ // run-rustfix #![warn(clippy::implicit_return)] -#![allow(clippy::needless_return, unused)] +#![allow(clippy::needless_return, clippy::needless_bool, unused, clippy::never_loop)] fn test_end_of_fn() -> bool { if true { @@ -12,7 +12,6 @@ fn test_end_of_fn() -> bool { return true } -#[allow(clippy::needless_bool)] fn test_if_block() -> bool { if true { return true } else { return false } } @@ -25,7 +24,6 @@ fn test_match(x: bool) -> bool { } } -#[allow(clippy::needless_return)] fn test_match_with_unreachable(x: bool) -> bool { match x { true => return false, @@ -33,14 +31,12 @@ fn test_match_with_unreachable(x: bool) -> bool { } } -#[allow(clippy::never_loop)] fn test_loop() -> bool { loop { return true; } } -#[allow(clippy::never_loop)] fn test_loop_with_block() -> bool { loop { { @@ -49,7 +45,6 @@ fn test_loop_with_block() -> bool { } } -#[allow(clippy::never_loop)] fn test_loop_with_nests() -> bool { loop { if true { @@ -83,15 +78,48 @@ fn test_return_macro() -> String { return format!("test {}", "test") } -fn main() { - let _ = test_end_of_fn(); - let _ = test_if_block(); - let _ = test_match(true); - let _ = test_match_with_unreachable(true); - let _ = test_loop(); - let _ = test_loop_with_block(); - let _ = test_loop_with_nests(); - let _ = test_loop_with_if_let(); - test_closure(); - let _ = test_return_macro(); +fn macro_branch_test() -> bool { + macro_rules! m { + ($t:expr, $f:expr) => { + if true { $t } else { $f } + }; + } + return m!(true, false) +} + +fn loop_test() -> bool { + 'outer: loop { + if true { + return true; + } + + let _ = loop { + if false { + return false; + } + if true { + break true; + } + }; + } } + +fn loop_macro_test() -> bool { + macro_rules! m { + ($e:expr) => { + break $e + }; + } + return loop { + m!(true); + } +} + +fn divergent_test() -> bool { + fn diverge() -> ! { + panic!() + } + diverge() +} + +fn main() {} diff --git a/tests/ui/implicit_return.rs b/tests/ui/implicit_return.rs index 2c1bc046515..737ffd5ddce 100644 --- a/tests/ui/implicit_return.rs +++ b/tests/ui/implicit_return.rs @@ -1,7 +1,7 @@ // run-rustfix #![warn(clippy::implicit_return)] -#![allow(clippy::needless_return, unused)] +#![allow(clippy::needless_return, clippy::needless_bool, unused, clippy::never_loop)] fn test_end_of_fn() -> bool { if true { @@ -12,7 +12,6 @@ fn test_end_of_fn() -> bool { true } -#[allow(clippy::needless_bool)] fn test_if_block() -> bool { if true { true } else { false } } @@ -25,7 +24,6 @@ fn test_match(x: bool) -> bool { } } -#[allow(clippy::needless_return)] fn test_match_with_unreachable(x: bool) -> bool { match x { true => return false, @@ -33,14 +31,12 @@ fn test_match_with_unreachable(x: bool) -> bool { } } -#[allow(clippy::never_loop)] fn test_loop() -> bool { loop { break true; } } -#[allow(clippy::never_loop)] fn test_loop_with_block() -> bool { loop { { @@ -49,7 +45,6 @@ fn test_loop_with_block() -> bool { } } -#[allow(clippy::never_loop)] fn test_loop_with_nests() -> bool { loop { if true { @@ -83,15 +78,48 @@ fn test_return_macro() -> String { format!("test {}", "test") } -fn main() { - let _ = test_end_of_fn(); - let _ = test_if_block(); - let _ = test_match(true); - let _ = test_match_with_unreachable(true); - let _ = test_loop(); - let _ = test_loop_with_block(); - let _ = test_loop_with_nests(); - let _ = test_loop_with_if_let(); - test_closure(); - let _ = test_return_macro(); +fn macro_branch_test() -> bool { + macro_rules! m { + ($t:expr, $f:expr) => { + if true { $t } else { $f } + }; + } + m!(true, false) } + +fn loop_test() -> bool { + 'outer: loop { + if true { + break true; + } + + let _ = loop { + if false { + break 'outer false; + } + if true { + break true; + } + }; + } +} + +fn loop_macro_test() -> bool { + macro_rules! m { + ($e:expr) => { + break $e + }; + } + loop { + m!(true); + } +} + +fn divergent_test() -> bool { + fn diverge() -> ! { + panic!() + } + diverge() +} + +fn main() {} diff --git a/tests/ui/implicit_return.stderr b/tests/ui/implicit_return.stderr index 3608319e5bd..632e30cbdc6 100644 --- a/tests/ui/implicit_return.stderr +++ b/tests/ui/implicit_return.stderr @@ -7,64 +7,97 @@ LL | true = note: `-D clippy::implicit-return` implied by `-D warnings` error: missing `return` statement - --> $DIR/implicit_return.rs:17:15 + --> $DIR/implicit_return.rs:16:15 | LL | if true { true } else { false } | ^^^^ help: add `return` as shown: `return true` error: missing `return` statement - --> $DIR/implicit_return.rs:17:29 + --> $DIR/implicit_return.rs:16:29 | LL | if true { true } else { false } | ^^^^^ help: add `return` as shown: `return false` error: missing `return` statement - --> $DIR/implicit_return.rs:23:17 + --> $DIR/implicit_return.rs:22:17 | LL | true => false, | ^^^^^ help: add `return` as shown: `return false` error: missing `return` statement - --> $DIR/implicit_return.rs:24:20 + --> $DIR/implicit_return.rs:23:20 | LL | false => { true }, | ^^^^ help: add `return` as shown: `return true` error: missing `return` statement - --> $DIR/implicit_return.rs:39:9 + --> $DIR/implicit_return.rs:36:9 | LL | break true; | ^^^^^^^^^^ help: change `break` to `return` as shown: `return true` error: missing `return` statement - --> $DIR/implicit_return.rs:47:13 + --> $DIR/implicit_return.rs:43:13 | LL | break true; | ^^^^^^^^^^ help: change `break` to `return` as shown: `return true` error: missing `return` statement - --> $DIR/implicit_return.rs:56:13 + --> $DIR/implicit_return.rs:51:13 | LL | break true; | ^^^^^^^^^^ help: change `break` to `return` as shown: `return true` error: missing `return` statement - --> $DIR/implicit_return.rs:74:18 + --> $DIR/implicit_return.rs:69:18 | LL | let _ = || { true }; | ^^^^ help: add `return` as shown: `return true` error: missing `return` statement - --> $DIR/implicit_return.rs:75:16 + --> $DIR/implicit_return.rs:70:16 | LL | let _ = || true; | ^^^^ help: add `return` as shown: `return true` error: missing `return` statement - --> $DIR/implicit_return.rs:83:5 + --> $DIR/implicit_return.rs:78:5 | LL | format!("test {}", "test") | ^^^^^^^^^^^^^^^^^^^^^^^^^^ help: add `return` as shown: `return format!("test {}", "test")` -error: aborting due to 11 previous errors +error: missing `return` statement + --> $DIR/implicit_return.rs:87:5 + | +LL | m!(true, false) + | ^^^^^^^^^^^^^^^ help: add `return` as shown: `return m!(true, false)` + +error: missing `return` statement + --> $DIR/implicit_return.rs:93:13 + | +LL | break true; + | ^^^^^^^^^^ help: change `break` to `return` as shown: `return true` + +error: missing `return` statement + --> $DIR/implicit_return.rs:98:17 + | +LL | break 'outer false; + | ^^^^^^^^^^^^^^^^^^ help: change `break` to `return` as shown: `return false` + +error: missing `return` statement + --> $DIR/implicit_return.rs:113:5 + | +LL | / loop { +LL | | m!(true); +LL | | } + | |_____^ + | +help: add `return` as shown + | +LL | return loop { +LL | m!(true); +LL | } + | + +error: aborting due to 15 previous errors -- 2.44.0