use if_chain::if_chain;
+use rustc::declare_lint_pass;
use rustc::lint::{in_external_macro, EarlyContext, EarlyLintPass, LintArray, LintContext, LintPass};
-use rustc::{declare_lint_pass, declare_tool_lint};
use rustc_errors::Applicability;
+use rustc_session::declare_tool_lint;
use syntax::ast;
use syntax::source_map::Span;
use syntax::visit::FnKind;
use syntax_pos::BytePos;
-use crate::utils::sym;
-use crate::utils::{in_macro_or_desugar, match_path_ast, snippet_opt, span_lint_and_then, span_note_and_lint};
+use crate::utils::{match_path_ast, snippet_opt, span_lint_and_then};
declare_clippy_lint! {
/// **What it does:** Checks for return statements at the end of a block.
"needless unit expression"
}
+#[derive(PartialEq, Eq, Copy, Clone)]
+enum RetReplacement {
+ Empty,
+ Block,
+}
+
declare_lint_pass!(Return => [NEEDLESS_RETURN, LET_AND_RETURN, UNUSED_UNIT]);
impl Return {
// Check the final stmt or expr in a block for unnecessary return.
fn check_block_return(&mut self, cx: &EarlyContext<'_>, block: &ast::Block) {
if let Some(stmt) = block.stmts.last() {
- match stmt.node {
+ match stmt.kind {
ast::StmtKind::Expr(ref expr) | ast::StmtKind::Semi(ref expr) => {
- self.check_final_expr(cx, expr, Some(stmt.span));
+ self.check_final_expr(cx, expr, Some(stmt.span), RetReplacement::Empty);
},
_ => (),
}
}
// Check a the final expression in a block if it's a return.
- fn check_final_expr(&mut self, cx: &EarlyContext<'_>, expr: &ast::Expr, span: Option<Span>) {
- match expr.node {
+ fn check_final_expr(
+ &mut self,
+ cx: &EarlyContext<'_>,
+ expr: &ast::Expr,
+ span: Option<Span>,
+ replacement: RetReplacement,
+ ) {
+ match expr.kind {
// simple return is always "bad"
- ast::ExprKind::Ret(Some(ref inner)) => {
+ ast::ExprKind::Ret(ref inner) => {
// allow `#[cfg(a)] return a; #[cfg(b)] return b;`
if !expr.attrs.iter().any(attr_is_cfg) {
- self.emit_return_lint(cx, span.expect("`else return` is not possible"), inner.span);
+ Self::emit_return_lint(
+ cx,
+ span.expect("`else return` is not possible"),
+ inner.as_ref().map(|i| i.span),
+ replacement,
+ );
}
},
// a whole block? check it!
// (except for unit type functions) so we don't match it
ast::ExprKind::If(_, ref ifblock, Some(ref elsexpr)) => {
self.check_block_return(cx, ifblock);
- self.check_final_expr(cx, elsexpr, None);
+ self.check_final_expr(cx, elsexpr, None, RetReplacement::Empty);
},
// a match expr, check all arms
ast::ExprKind::Match(_, ref arms) => {
for arm in arms {
- self.check_final_expr(cx, &arm.body, Some(arm.body.span));
+ self.check_final_expr(cx, &arm.body, Some(arm.body.span), RetReplacement::Block);
}
},
_ => (),
}
}
- fn emit_return_lint(&mut self, cx: &EarlyContext<'_>, ret_span: Span, inner_span: Span) {
- if in_external_macro(cx.sess(), inner_span) || in_macro_or_desugar(inner_span) {
- return;
+ fn emit_return_lint(cx: &EarlyContext<'_>, ret_span: Span, inner_span: Option<Span>, replacement: RetReplacement) {
+ match inner_span {
+ Some(inner_span) => {
+ if in_external_macro(cx.sess(), inner_span) || inner_span.from_expansion() {
+ return;
+ }
+
+ span_lint_and_then(cx, NEEDLESS_RETURN, ret_span, "unneeded return statement", |db| {
+ if let Some(snippet) = snippet_opt(cx, inner_span) {
+ db.span_suggestion(ret_span, "remove `return`", snippet, Applicability::MachineApplicable);
+ }
+ })
+ },
+ None => match replacement {
+ RetReplacement::Empty => {
+ span_lint_and_then(cx, NEEDLESS_RETURN, ret_span, "unneeded return statement", |db| {
+ db.span_suggestion(
+ ret_span,
+ "remove `return`",
+ String::new(),
+ Applicability::MachineApplicable,
+ );
+ });
+ },
+ RetReplacement::Block => {
+ span_lint_and_then(cx, NEEDLESS_RETURN, ret_span, "unneeded return statement", |db| {
+ db.span_suggestion(
+ ret_span,
+ "replace `return` with an empty block",
+ "{}".to_string(),
+ Applicability::MachineApplicable,
+ );
+ });
+ },
+ },
}
- span_lint_and_then(cx, NEEDLESS_RETURN, ret_span, "unneeded return statement", |db| {
- if let Some(snippet) = snippet_opt(cx, inner_span) {
- db.span_suggestion(
- ret_span,
- "remove `return` as shown",
- snippet,
- Applicability::MachineApplicable,
- );
- }
- });
}
// Check for "let x = EXPR; x"
- fn check_let_return(&mut self, cx: &EarlyContext<'_>, block: &ast::Block) {
+ fn check_let_return(cx: &EarlyContext<'_>, block: &ast::Block) {
let mut it = block.stmts.iter();
// we need both a let-binding stmt and an expr
if_chain! {
if let Some(retexpr) = it.next_back();
- if let ast::StmtKind::Expr(ref retexpr) = retexpr.node;
+ if let ast::StmtKind::Expr(ref retexpr) = retexpr.kind;
if let Some(stmt) = it.next_back();
- if let ast::StmtKind::Local(ref local) = stmt.node;
+ if let ast::StmtKind::Local(ref local) = stmt.kind;
// don't lint in the presence of type inference
if local.ty.is_none();
if local.attrs.is_empty();
if let Some(ref initexpr) = local.init;
- if let ast::PatKind::Ident(_, ident, _) = local.pat.node;
- if let ast::ExprKind::Path(_, ref path) = retexpr.node;
- if match_path_ast(path, &[ident.name]);
+ if let ast::PatKind::Ident(_, ident, _) = local.pat.kind;
+ if let ast::ExprKind::Path(_, ref path) = retexpr.kind;
+ if match_path_ast(path, &[&*ident.name.as_str()]);
if !in_external_macro(cx.sess(), initexpr.span);
+ if !in_external_macro(cx.sess(), retexpr.span);
+ if !in_external_macro(cx.sess(), local.span);
then {
- span_note_and_lint(cx,
- LET_AND_RETURN,
- retexpr.span,
- "returning the result of a let binding from a block. \
- Consider returning the expression directly.",
- initexpr.span,
- "this expression can be directly returned");
+ span_lint_and_then(
+ cx,
+ LET_AND_RETURN,
+ retexpr.span,
+ "returning the result of a let binding from a block",
+ |err| {
+ err.span_label(local.span, "unnecessary let binding");
+
+ if let Some(snippet) = snippet_opt(cx, initexpr.span) {
+ err.multipart_suggestion(
+ "return the expression directly",
+ vec![
+ (local.span, String::new()),
+ (retexpr.span, snippet),
+ ],
+ Applicability::MachineApplicable,
+ );
+ } else {
+ err.span_help(initexpr.span, "this expression can be directly returned");
+ }
+ },
+ );
}
}
}
fn check_fn(&mut self, cx: &EarlyContext<'_>, kind: FnKind<'_>, decl: &ast::FnDecl, span: Span, _: ast::NodeId) {
match kind {
FnKind::ItemFn(.., block) | FnKind::Method(.., block) => self.check_block_return(cx, block),
- FnKind::Closure(body) => self.check_final_expr(cx, body, Some(body.span)),
+ FnKind::Closure(body) => self.check_final_expr(cx, body, Some(body.span), RetReplacement::Empty),
}
if_chain! {
if let ast::FunctionRetTy::Ty(ref ty) = decl.output;
- if let ast::TyKind::Tup(ref vals) = ty.node;
- if vals.is_empty() && !in_macro_or_desugar(ty.span) && get_def(span) == get_def(ty.span);
+ if let ast::TyKind::Tup(ref vals) = ty.kind;
+ if vals.is_empty() && !ty.span.from_expansion() && get_def(span) == get_def(ty.span);
then {
let (rspan, appl) = if let Ok(fn_source) =
cx.sess().source_map()
}
fn check_block(&mut self, cx: &EarlyContext<'_>, block: &ast::Block) {
- self.check_let_return(cx, block);
+ Self::check_let_return(cx, block);
if_chain! {
if let Some(ref stmt) = block.stmts.last();
- if let ast::StmtKind::Expr(ref expr) = stmt.node;
- if is_unit_expr(expr) && !in_macro_or_desugar(expr.span);
+ if let ast::StmtKind::Expr(ref expr) = stmt.kind;
+ if is_unit_expr(expr) && !stmt.span.from_expansion();
then {
let sp = expr.span;
span_lint_and_then(cx, UNUSED_UNIT, sp, "unneeded unit expression", |db| {
}
fn check_expr(&mut self, cx: &EarlyContext<'_>, e: &ast::Expr) {
- match e.node {
+ match e.kind {
ast::ExprKind::Ret(Some(ref expr)) | ast::ExprKind::Break(_, Some(ref expr)) => {
- if is_unit_expr(expr) && !in_macro_or_desugar(expr.span) {
+ if is_unit_expr(expr) && !expr.span.from_expansion() {
span_lint_and_then(cx, UNUSED_UNIT, expr.span, "unneeded `()`", |db| {
db.span_suggestion(
expr.span,
}
fn attr_is_cfg(attr: &ast::Attribute) -> bool {
- attr.meta_item_list().is_some() && attr.check_name(*sym::cfg)
+ attr.meta_item_list().is_some() && attr.check_name(sym!(cfg))
}
// get the def site
+#[must_use]
fn get_def(span: Span) -> Option<Span> {
- span.ctxt().outer().expn_info().and_then(|info| info.def_site)
+ if span.from_expansion() {
+ Some(span.ctxt().outer_expn_data().def_site)
+ } else {
+ None
+ }
}
// is this expr a `()` unit?
fn is_unit_expr(expr: &ast::Expr) -> bool {
- if let ast::ExprKind::Tup(ref vals) = expr.node {
+ if let ast::ExprKind::Tup(ref vals) = expr.kind {
vals.is_empty()
} else {
false
projects / rust.git / blobdiff