-use syntax::ast;
+use rustc::lint::*;
use syntax::ast::*;
+// use reexport::*;
use syntax::codemap::{Span, Spanned};
use syntax::visit::FnKind;
-use rustc::lint::{Context, LintPass, LintArray, Level};
-use utils::{span_lint, snippet, match_path};
+use utils::{span_lint, span_lint_and_then, snippet_opt, match_path_ast, in_external_macro};
+/// **What it does:** This lint checks for return statements at the end of a block. It is `Warn` by default.
+///
+/// **Why is this bad?** Removing the `return` and semicolon will make the code more rusty.
+///
+/// **Known problems:** None
+///
+/// **Example:** `fn foo(x: usize) { return x; }`
declare_lint!(pub NEEDLESS_RETURN, Warn,
- "Warn on using a return statement where an expression would be enough");
+ "using a return statement like `return expr;` where an expression would suffice");
+/// **What it does:** This lint checks for `let`-bindings, which are subsequently returned. It is `Warn` by default.
+///
+/// **Why is this bad?** It is just extraneous code. Remove it to make your code more rusty.
+///
+/// **Known problems:** None
+///
+/// **Example:** `{ let x = ..; x }`
declare_lint!(pub LET_AND_RETURN, Warn,
- "Warn on creating a let-binding and then immediately returning it");
+ "creating a let-binding and then immediately returning it like `let x = expr; x` at \
+ the end of a block");
-#[derive(Copy,Clone)]
+#[derive(Copy, Clone)]
pub struct ReturnPass;
impl ReturnPass {
// Check the final stmt or expr in a block for unnecessary return.
- fn check_block_return(&mut self, cx: &Context, block: &Block) {
+ fn check_block_return(&mut self, cx: &EarlyContext, block: &Block) {
if let Some(ref expr) = block.expr {
self.check_final_expr(cx, expr);
} else if let Some(stmt) = block.stmts.last() {
if let StmtSemi(ref expr, _) = stmt.node {
if let ExprRet(Some(ref inner)) = expr.node {
- self.emit_return_lint(cx, (expr.span, inner.span));
+ self.emit_return_lint(cx, (stmt.span, inner.span));
}
}
}
}
// Check a the final expression in a block if it's a return.
- fn check_final_expr(&mut self, cx: &Context, expr: &Expr) {
+ fn check_final_expr(&mut self, cx: &EarlyContext, expr: &Expr) {
match expr.node {
// simple return is always "bad"
ExprRet(Some(ref inner)) => {
// an if/if let expr, check both exprs
// note, if without else is going to be a type checking error anyways
// (except for unit type functions) so we don't match it
- ExprIf(_, ref ifblock, Some(ref elsexpr)) |
- ExprIfLet(_, _, ref ifblock, Some(ref elsexpr)) => {
+ ExprIf(_, ref ifblock, Some(ref elsexpr)) => {
self.check_block_return(cx, ifblock);
self.check_final_expr(cx, elsexpr);
}
// a match expr, check all arms
- ExprMatch(_, ref arms, _) => {
+ ExprMatch(_, ref arms) => {
for arm in arms {
- self.check_final_expr(cx, &*arm.body);
+ self.check_final_expr(cx, &arm.body);
}
}
- _ => { }
+ _ => {}
}
}
- fn emit_return_lint(&mut self, cx: &Context, spans: (Span, Span)) {
- span_lint(cx, NEEDLESS_RETURN, spans.0, &format!(
- "unneeded return statement. Consider using `{}` \
- without the trailing semicolon",
- snippet(cx, spans.1, "..")))
+ fn emit_return_lint(&mut self, cx: &EarlyContext, spans: (Span, Span)) {
+ if in_external_macro(cx, spans.1) {
+ return;
+ }
+ span_lint_and_then(cx, NEEDLESS_RETURN, spans.0, "unneeded return statement", |db| {
+ if let Some(snippet) = snippet_opt(cx, spans.1) {
+ db.span_suggestion(spans.0, "remove `return` as shown:", snippet);
+ }
+ });
}
// Check for "let x = EXPR; x"
- fn check_let_return(&mut self, cx: &Context, block: &Block) {
+ fn check_let_return(&mut self, cx: &EarlyContext, block: &Block) {
// we need both a let-binding stmt and an expr
if_let_chain! {
[
let Some(stmt) = block.stmts.last(),
+ let Some(ref retexpr) = block.expr,
let StmtDecl(ref decl, _) = stmt.node,
let DeclLocal(ref local) = decl.node,
let Some(ref initexpr) = local.init,
let PatIdent(_, Spanned { node: id, .. }, _) = local.pat.node,
- let Some(ref retexpr) = block.expr,
let ExprPath(_, ref path) = retexpr.node,
- match_path(path, &[&*id.name.as_str()])
+ match_path_ast(path, &[&id.name.as_str()])
], {
self.emit_let_lint(cx, retexpr.span, initexpr.span);
}
}
}
- fn emit_let_lint(&mut self, cx: &Context, lint_span: Span, note_span: Span) {
- span_lint(cx, LET_AND_RETURN, lint_span,
- "returning the result of a let binding. \
- Consider returning the expression directly.");
+ fn emit_let_lint(&mut self, cx: &EarlyContext, lint_span: Span, note_span: Span) {
+ if in_external_macro(cx, note_span) {
+ return;
+ }
+ let mut db = span_lint(cx,
+ LET_AND_RETURN,
+ lint_span,
+ "returning the result of a let binding from a block. Consider returning the \
+ expression directly.");
if cx.current_level(LET_AND_RETURN) != Level::Allow {
- cx.sess().span_note(note_span,
- "this expression can be directly returned");
+ db.span_note(note_span, "this expression can be directly returned");
}
}
}
fn get_lints(&self) -> LintArray {
lint_array!(NEEDLESS_RETURN, LET_AND_RETURN)
}
+}
- fn check_fn(&mut self, cx: &Context, _: FnKind, _: &FnDecl,
- block: &Block, _: Span, _: ast::NodeId) {
+impl EarlyLintPass for ReturnPass {
+ fn check_fn(&mut self, cx: &EarlyContext, _: FnKind, _: &FnDecl, block: &Block, _: Span, _: NodeId) {
self.check_block_return(cx, block);
+ }
+
+ fn check_block(&mut self, cx: &EarlyContext, block: &Block) {
self.check_let_return(cx, block);
}
}
projects / rust.git / blobdiff