3a96d6b603
for file in `fd \.rs$` ; do sed -i s/span_suggestion_with_applicability/span_suggestion/g $file ; done for file in `fd \.rs$` ; do sed -i s/span_suggestion_short_with_applicability/span_suggestion_short/g $file ; done for file in `fd \.rs$` ; do sed -i s/span_suggestions_with_applicability/span_suggestions/g $file ; done
265 lines
8.4 KiB
Rust
265 lines
8.4 KiB
Rust
use crate::utils::paths;
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use crate::utils::{in_macro, iter_input_pats, match_type, method_chain_args, snippet, span_lint_and_then};
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use if_chain::if_chain;
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use rustc::hir;
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use rustc::lint::{LateContext, LateLintPass, LintArray, LintPass};
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use rustc::ty;
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use rustc::{declare_tool_lint, lint_array};
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use rustc_errors::Applicability;
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use syntax::source_map::Span;
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#[derive(Clone)]
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pub struct Pass;
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/// **What it does:** Checks for usage of `option.map(f)` where f is a function
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/// or closure that returns the unit type.
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///
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/// **Why is this bad?** Readability, this can be written more clearly with
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/// an if let statement
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///
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/// **Known problems:** None.
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///
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/// **Example:**
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///
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/// ```rust
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/// let x: Option<&str> = do_stuff();
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/// x.map(log_err_msg);
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/// x.map(|msg| log_err_msg(format_msg(msg)))
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/// ```
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///
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/// The correct use would be:
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///
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/// ```rust
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/// let x: Option<&str> = do_stuff();
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/// if let Some(msg) = x {
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/// log_err_msg(msg)
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/// }
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/// if let Some(msg) = x {
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/// log_err_msg(format_msg(msg))
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/// }
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/// ```
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declare_clippy_lint! {
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pub OPTION_MAP_UNIT_FN,
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complexity,
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"using `option.map(f)`, where f is a function or closure that returns ()"
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}
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/// **What it does:** Checks for usage of `result.map(f)` where f is a function
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/// or closure that returns the unit type.
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///
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/// **Why is this bad?** Readability, this can be written more clearly with
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/// an if let statement
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///
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/// **Known problems:** None.
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///
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/// **Example:**
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///
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/// ```rust
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/// let x: Result<&str, &str> = do_stuff();
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/// x.map(log_err_msg);
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/// x.map(|msg| log_err_msg(format_msg(msg)))
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/// ```
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///
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/// The correct use would be:
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///
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/// ```rust
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/// let x: Result<&str, &str> = do_stuff();
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/// if let Ok(msg) = x {
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/// log_err_msg(msg)
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/// }
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/// if let Ok(msg) = x {
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/// log_err_msg(format_msg(msg))
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/// }
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/// ```
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declare_clippy_lint! {
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pub RESULT_MAP_UNIT_FN,
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complexity,
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"using `result.map(f)`, where f is a function or closure that returns ()"
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}
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impl LintPass for Pass {
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fn get_lints(&self) -> LintArray {
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lint_array!(OPTION_MAP_UNIT_FN, RESULT_MAP_UNIT_FN)
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}
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fn name(&self) -> &'static str {
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"MapUnit"
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}
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}
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fn is_unit_type(ty: ty::Ty<'_>) -> bool {
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match ty.sty {
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ty::Tuple(slice) => slice.is_empty(),
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ty::Never => true,
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_ => false,
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}
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}
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fn is_unit_function(cx: &LateContext<'_, '_>, expr: &hir::Expr) -> bool {
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let ty = cx.tables.expr_ty(expr);
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if let ty::FnDef(id, _) = ty.sty {
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if let Some(fn_type) = cx.tcx.fn_sig(id).no_bound_vars() {
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return is_unit_type(fn_type.output());
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}
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}
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false
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}
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fn is_unit_expression(cx: &LateContext<'_, '_>, expr: &hir::Expr) -> bool {
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is_unit_type(cx.tables.expr_ty(expr))
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}
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/// The expression inside a closure may or may not have surrounding braces and
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/// semicolons, which causes problems when generating a suggestion. Given an
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/// expression that evaluates to '()' or '!', recursively remove useless braces
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/// and semi-colons until is suitable for including in the suggestion template
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fn reduce_unit_expression<'a>(cx: &LateContext<'_, '_>, expr: &'a hir::Expr) -> Option<Span> {
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if !is_unit_expression(cx, expr) {
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return None;
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}
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match expr.node {
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hir::ExprKind::Call(_, _) | hir::ExprKind::MethodCall(_, _, _) => {
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// Calls can't be reduced any more
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Some(expr.span)
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},
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hir::ExprKind::Block(ref block, _) => {
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match (&block.stmts[..], block.expr.as_ref()) {
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(&[], Some(inner_expr)) => {
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// If block only contains an expression,
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// reduce `{ X }` to `X`
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reduce_unit_expression(cx, inner_expr)
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},
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(&[ref inner_stmt], None) => {
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// If block only contains statements,
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// reduce `{ X; }` to `X` or `X;`
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match inner_stmt.node {
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hir::StmtKind::Local(ref local) => Some(local.span),
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hir::StmtKind::Expr(ref e) => Some(e.span),
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hir::StmtKind::Semi(..) => Some(inner_stmt.span),
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hir::StmtKind::Item(..) => None,
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}
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},
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_ => {
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// For closures that contain multiple statements
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// it's difficult to get a correct suggestion span
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// for all cases (multi-line closures specifically)
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//
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// We do not attempt to build a suggestion for those right now.
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None
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},
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}
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},
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_ => None,
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}
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}
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fn unit_closure<'a, 'tcx>(cx: &LateContext<'a, 'tcx>, expr: &'a hir::Expr) -> Option<(&'tcx hir::Arg, &'a hir::Expr)> {
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if let hir::ExprKind::Closure(_, ref decl, inner_expr_id, _, _) = expr.node {
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let body = cx.tcx.hir().body(inner_expr_id);
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let body_expr = &body.value;
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if_chain! {
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if decl.inputs.len() == 1;
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if is_unit_expression(cx, body_expr);
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if let Some(binding) = iter_input_pats(&decl, body).next();
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then {
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return Some((binding, body_expr));
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}
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}
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}
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None
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}
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/// Builds a name for the let binding variable (`var_arg`)
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///
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/// `x.field` => `x_field`
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/// `y` => `_y`
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///
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/// Anything else will return `_`.
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fn let_binding_name(cx: &LateContext<'_, '_>, var_arg: &hir::Expr) -> String {
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match &var_arg.node {
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hir::ExprKind::Field(_, _) => snippet(cx, var_arg.span, "_").replace(".", "_"),
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hir::ExprKind::Path(_) => format!("_{}", snippet(cx, var_arg.span, "")),
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_ => "_".to_string(),
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}
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}
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fn suggestion_msg(function_type: &str, map_type: &str) -> String {
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format!(
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"called `map(f)` on an {0} value where `f` is a unit {1}",
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map_type, function_type
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)
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}
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fn lint_map_unit_fn(cx: &LateContext<'_, '_>, stmt: &hir::Stmt, expr: &hir::Expr, map_args: &[hir::Expr]) {
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let var_arg = &map_args[0];
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let (map_type, variant, lint) = if match_type(cx, cx.tables.expr_ty(var_arg), &paths::OPTION) {
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("Option", "Some", OPTION_MAP_UNIT_FN)
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} else if match_type(cx, cx.tables.expr_ty(var_arg), &paths::RESULT) {
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("Result", "Ok", RESULT_MAP_UNIT_FN)
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} else {
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return;
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};
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let fn_arg = &map_args[1];
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if is_unit_function(cx, fn_arg) {
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let msg = suggestion_msg("function", map_type);
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let suggestion = format!(
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"if let {0}({1}) = {2} {{ {3}(...) }}",
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variant,
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let_binding_name(cx, var_arg),
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snippet(cx, var_arg.span, "_"),
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snippet(cx, fn_arg.span, "_")
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);
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span_lint_and_then(cx, lint, expr.span, &msg, |db| {
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db.span_suggestion(stmt.span, "try this", suggestion, Applicability::Unspecified);
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});
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} else if let Some((binding, closure_expr)) = unit_closure(cx, fn_arg) {
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let msg = suggestion_msg("closure", map_type);
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span_lint_and_then(cx, lint, expr.span, &msg, |db| {
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if let Some(reduced_expr_span) = reduce_unit_expression(cx, closure_expr) {
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let suggestion = format!(
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"if let {0}({1}) = {2} {{ {3} }}",
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variant,
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snippet(cx, binding.pat.span, "_"),
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snippet(cx, var_arg.span, "_"),
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snippet(cx, reduced_expr_span, "_")
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);
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db.span_suggestion(
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stmt.span,
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"try this",
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suggestion,
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Applicability::MachineApplicable, // snippet
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);
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} else {
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let suggestion = format!(
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"if let {0}({1}) = {2} {{ ... }}",
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variant,
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snippet(cx, binding.pat.span, "_"),
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snippet(cx, var_arg.span, "_")
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);
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db.span_suggestion(stmt.span, "try this", suggestion, Applicability::Unspecified);
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}
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});
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}
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}
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impl<'a, 'tcx> LateLintPass<'a, 'tcx> for Pass {
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fn check_stmt(&mut self, cx: &LateContext<'_, '_>, stmt: &hir::Stmt) {
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if in_macro(stmt.span) {
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return;
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}
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if let hir::StmtKind::Semi(ref expr) = stmt.node {
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if let Some(arglists) = method_chain_args(expr, &["map"]) {
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lint_map_unit_fn(cx, stmt, expr, arglists[0]);
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}
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}
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}
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}
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