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Auto merge of #5957 - xvschneider:AddUnwrapInsideResultLint, r=yaahc
Adding new lint to prevent usage of 'unwrap' inside functions that re… ### Change Adding a new lint that will emit a warning when using "unwrap" or "expect" inside a function that returns result. ### Motivation These functions promote recoverable errors to non-recoverable errors which may be undesirable in code bases which wish to avoid panics. ### Test plan Running: `TESTNAME=unwrap_in_result cargo uitest `--- changelog: none
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,140 @@ | ||
| use crate::utils::{is_type_diagnostic_item, method_chain_args, return_ty, span_lint_and_then, walk_ptrs_ty}; | ||
| use if_chain::if_chain; | ||
| use rustc_hir as hir; | ||
| use rustc_lint::{LateContext, LateLintPass}; | ||
| use rustc_middle::hir::map::Map; | ||
| use rustc_middle::ty; | ||
| use rustc_session::{declare_lint_pass, declare_tool_lint}; | ||
| use rustc_span::Span; | ||
|
|
||
| declare_clippy_lint! { | ||
| /// **What it does:** Checks for functions of type Result that contain `expect()` or `unwrap()` | ||
| /// | ||
| /// **Why is this bad?** These functions promote recoverable errors to non-recoverable errors which may be undesirable in code bases which wish to avoid panics. | ||
| /// | ||
| /// **Known problems:** This can cause false positives in functions that handle both recoverable and non recoverable errors. | ||
| /// | ||
| /// **Example:** | ||
| /// Before: | ||
| /// ```rust | ||
| /// fn divisible_by_3(i_str: String) -> Result<(), String> { | ||
| /// let i = i_str | ||
| /// .parse::<i32>() | ||
| /// .expect("cannot divide the input by three"); | ||
| /// | ||
| /// if i % 3 != 0 { | ||
| /// Err("Number is not divisible by 3")? | ||
| /// } | ||
| /// | ||
| /// Ok(()) | ||
| /// } | ||
| /// ``` | ||
| /// | ||
| /// After: | ||
| /// ```rust | ||
| /// fn divisible_by_3(i_str: String) -> Result<(), String> { | ||
| /// let i = i_str | ||
| /// .parse::<i32>() | ||
| /// .map_err(|e| format!("cannot divide the input by three: {}", e))?; | ||
| /// | ||
| /// if i % 3 != 0 { | ||
| /// Err("Number is not divisible by 3")? | ||
| /// } | ||
| /// | ||
| /// Ok(()) | ||
| /// } | ||
| /// ``` | ||
| pub UNWRAP_IN_RESULT, | ||
| restriction, | ||
| "functions of type `Result<..>` or `Option`<...> that contain `expect()` or `unwrap()`" | ||
| } | ||
|
|
||
| declare_lint_pass!(UnwrapInResult=> [UNWRAP_IN_RESULT]); | ||
|
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||
| impl<'tcx> LateLintPass<'tcx> for UnwrapInResult { | ||
| fn check_impl_item(&mut self, cx: &LateContext<'tcx>, impl_item: &'tcx hir::ImplItem<'_>) { | ||
| if_chain! { | ||
| // first check if it's a method or function | ||
| if let hir::ImplItemKind::Fn(ref _signature, _) = impl_item.kind; | ||
| // checking if its return type is `result` or `option` | ||
| if is_type_diagnostic_item(cx, return_ty(cx, impl_item.hir_id), sym!(result_type)) | ||
| || is_type_diagnostic_item(cx, return_ty(cx, impl_item.hir_id), sym!(option_type)); | ||
| then { | ||
| lint_impl_body(cx, impl_item.span, impl_item); | ||
| } | ||
| } | ||
| } | ||
| } | ||
|
|
||
| use rustc_hir::intravisit::{self, NestedVisitorMap, Visitor}; | ||
| use rustc_hir::{Expr, ImplItemKind}; | ||
|
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||
| struct FindExpectUnwrap<'a, 'tcx> { | ||
| lcx: &'a LateContext<'tcx>, | ||
| typeck_results: &'tcx ty::TypeckResults<'tcx>, | ||
| result: Vec<Span>, | ||
| } | ||
|
|
||
| impl<'a, 'tcx> Visitor<'tcx> for FindExpectUnwrap<'a, 'tcx> { | ||
| type Map = Map<'tcx>; | ||
|
|
||
| fn visit_expr(&mut self, expr: &'tcx Expr<'_>) { | ||
| // check for `expect` | ||
| if let Some(arglists) = method_chain_args(expr, &["expect"]) { | ||
| let reciever_ty = walk_ptrs_ty(self.typeck_results.expr_ty(&arglists[0][0])); | ||
| if is_type_diagnostic_item(self.lcx, reciever_ty, sym!(option_type)) | ||
| || is_type_diagnostic_item(self.lcx, reciever_ty, sym!(result_type)) | ||
| { | ||
| self.result.push(expr.span); | ||
| } | ||
| } | ||
|
|
||
| // check for `unwrap` | ||
| if let Some(arglists) = method_chain_args(expr, &["unwrap"]) { | ||
| let reciever_ty = walk_ptrs_ty(self.typeck_results.expr_ty(&arglists[0][0])); | ||
| if is_type_diagnostic_item(self.lcx, reciever_ty, sym!(option_type)) | ||
| || is_type_diagnostic_item(self.lcx, reciever_ty, sym!(result_type)) | ||
| { | ||
| self.result.push(expr.span); | ||
| } | ||
| } | ||
|
|
||
| // and check sub-expressions | ||
| intravisit::walk_expr(self, expr); | ||
| } | ||
|
|
||
| fn nested_visit_map(&mut self) -> NestedVisitorMap<Self::Map> { | ||
| NestedVisitorMap::None | ||
| } | ||
| } | ||
|
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||
| fn lint_impl_body<'tcx>(cx: &LateContext<'tcx>, impl_span: Span, impl_item: &'tcx hir::ImplItem<'_>) { | ||
| if_chain! { | ||
|
|
||
| if let ImplItemKind::Fn(_, body_id) = impl_item.kind; | ||
| then { | ||
| let body = cx.tcx.hir().body(body_id); | ||
| let impl_item_def_id = cx.tcx.hir().local_def_id(impl_item.hir_id); | ||
| let mut fpu = FindExpectUnwrap { | ||
| lcx: cx, | ||
| typeck_results: cx.tcx.typeck(impl_item_def_id), | ||
| result: Vec::new(), | ||
| }; | ||
| fpu.visit_expr(&body.value); | ||
|
|
||
| // if we've found one, lint | ||
| if !fpu.result.is_empty() { | ||
| span_lint_and_then( | ||
| cx, | ||
| UNWRAP_IN_RESULT, | ||
| impl_span, | ||
| "used unwrap or expect in a function that returns result or option", | ||
| move |diag| { | ||
| diag.help( | ||
| "unwrap and expect should not be used in a function that returns result or option" ); | ||
| diag.span_note(fpu.result, "potential non-recoverable error(s)"); | ||
| }); | ||
| } | ||
| } | ||
| } | ||
| } |
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,44 @@ | ||
| #![warn(clippy::unwrap_in_result)] | ||
|
|
||
| struct A; | ||
|
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| impl A { | ||
| // should not be detected | ||
| fn good_divisible_by_3(i_str: String) -> Result<bool, String> { | ||
| // checks whether a string represents a number divisible by 3 | ||
| let i_result = i_str.parse::<i32>(); | ||
| match i_result { | ||
| Err(_e) => Err("Not a number".to_string()), | ||
| Ok(i) => { | ||
| if i % 3 == 0 { | ||
| return Ok(true); | ||
| } | ||
| Err("Number is not divisible by 3".to_string()) | ||
| }, | ||
| } | ||
| } | ||
|
|
||
| // should be detected | ||
| fn bad_divisible_by_3(i_str: String) -> Result<bool, String> { | ||
| // checks whether a string represents a number divisible by 3 | ||
| let i = i_str.parse::<i32>().unwrap(); | ||
| if i % 3 == 0 { | ||
| Ok(true) | ||
| } else { | ||
| Err("Number is not divisible by 3".to_string()) | ||
| } | ||
| } | ||
|
|
||
| fn example_option_expect(i_str: String) -> Option<bool> { | ||
| let i = i_str.parse::<i32>().expect("not a number"); | ||
| if i % 3 == 0 { | ||
| return Some(true); | ||
| } | ||
| None | ||
| } | ||
| } | ||
|
|
||
| fn main() { | ||
| A::bad_divisible_by_3("3".to_string()); | ||
| A::good_divisible_by_3("3".to_string()); | ||
| } |
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,41 @@ | ||
| error: used unwrap or expect in a function that returns result or option | ||
| --> $DIR/unwrap_in_result.rs:22:5 | ||
| | | ||
| LL | / fn bad_divisible_by_3(i_str: String) -> Result<bool, String> { | ||
| LL | | // checks whether a string represents a number divisible by 3 | ||
| LL | | let i = i_str.parse::<i32>().unwrap(); | ||
| LL | | if i % 3 == 0 { | ||
| ... | | ||
| LL | | } | ||
| LL | | } | ||
| | |_____^ | ||
| | | ||
| = note: `-D clippy::unwrap-in-result` implied by `-D warnings` | ||
| = help: unwrap and expect should not be used in a function that returns result or option | ||
| note: potential non-recoverable error(s) | ||
| --> $DIR/unwrap_in_result.rs:24:17 | ||
| | | ||
| LL | let i = i_str.parse::<i32>().unwrap(); | ||
| | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ | ||
|
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||
| error: used unwrap or expect in a function that returns result or option | ||
| --> $DIR/unwrap_in_result.rs:32:5 | ||
| | | ||
| LL | / fn example_option_expect(i_str: String) -> Option<bool> { | ||
| LL | | let i = i_str.parse::<i32>().expect("not a number"); | ||
| LL | | if i % 3 == 0 { | ||
| LL | | return Some(true); | ||
| LL | | } | ||
| LL | | None | ||
| LL | | } | ||
| | |_____^ | ||
| | | ||
| = help: unwrap and expect should not be used in a function that returns result or option | ||
| note: potential non-recoverable error(s) | ||
| --> $DIR/unwrap_in_result.rs:33:17 | ||
| | | ||
| LL | let i = i_str.parse::<i32>().expect("not a number"); | ||
| | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ | ||
|
|
||
| error: aborting due to 2 previous errors | ||
|
|