637 lines
22 KiB
Rust
637 lines
22 KiB
Rust
use crate::utils::{
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constants, snippet_opt, snippet_with_applicability, span_lint, span_lint_and_help, span_lint_and_sugg,
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span_lint_and_then,
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};
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use if_chain::if_chain;
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use rustc_ast::ast::{
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BindingMode, Block, Expr, ExprKind, GenericParamKind, Generics, Lit, LitFloatType, LitIntType, LitKind, Mutability,
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NodeId, Pat, PatKind, StmtKind, UnOp,
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};
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use rustc_ast::visit::{walk_expr, FnKind, Visitor};
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use rustc_data_structures::fx::FxHashMap;
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use rustc_errors::Applicability;
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use rustc_lint::{EarlyContext, EarlyLintPass, LintContext};
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use rustc_middle::lint::in_external_macro;
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use rustc_session::{declare_lint_pass, declare_tool_lint};
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use rustc_span::source_map::Span;
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declare_clippy_lint! {
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/// **What it does:** Checks for structure field patterns bound to wildcards.
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///
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/// **Why is this bad?** Using `..` instead is shorter and leaves the focus on
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/// the fields that are actually bound.
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///
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/// **Known problems:** None.
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///
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/// **Example:**
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/// ```ignore
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/// let { a: _, b: ref b, c: _ } = ..
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/// ```
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pub UNNEEDED_FIELD_PATTERN,
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restriction,
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"struct fields bound to a wildcard instead of using `..`"
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}
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declare_clippy_lint! {
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/// **What it does:** Checks for function arguments having the similar names
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/// differing by an underscore.
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///
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/// **Why is this bad?** It affects code readability.
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///
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/// **Known problems:** None.
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///
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/// **Example:**
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/// ```rust
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/// fn foo(a: i32, _a: i32) {}
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/// ```
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pub DUPLICATE_UNDERSCORE_ARGUMENT,
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style,
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"function arguments having names which only differ by an underscore"
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}
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declare_clippy_lint! {
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/// **What it does:** Detects closures called in the same expression where they
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/// are defined.
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///
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/// **Why is this bad?** It is unnecessarily adding to the expression's
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/// complexity.
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///
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/// **Known problems:** None.
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///
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/// **Example:**
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/// ```rust,ignore
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/// (|| 42)()
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/// ```
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pub REDUNDANT_CLOSURE_CALL,
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complexity,
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"throwaway closures called in the expression they are defined"
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}
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declare_clippy_lint! {
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/// **What it does:** Detects expressions of the form `--x`.
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///
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/// **Why is this bad?** It can mislead C/C++ programmers to think `x` was
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/// decremented.
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///
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/// **Known problems:** None.
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///
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/// **Example:**
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/// ```rust
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/// let mut x = 3;
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/// --x;
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/// ```
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pub DOUBLE_NEG,
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style,
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"`--x`, which is a double negation of `x` and not a pre-decrement as in C/C++"
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}
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declare_clippy_lint! {
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/// **What it does:** Warns on hexadecimal literals with mixed-case letter
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/// digits.
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///
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/// **Why is this bad?** It looks confusing.
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///
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/// **Known problems:** None.
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///
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/// **Example:**
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/// ```rust
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/// let y = 0x1a9BAcD;
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/// ```
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pub MIXED_CASE_HEX_LITERALS,
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style,
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"hex literals whose letter digits are not consistently upper- or lowercased"
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}
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declare_clippy_lint! {
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/// **What it does:** Warns if literal suffixes are not separated by an
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/// underscore.
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///
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/// **Why is this bad?** It is much less readable.
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///
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/// **Known problems:** None.
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///
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/// **Example:**
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/// ```rust
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/// let y = 123832i32;
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/// ```
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pub UNSEPARATED_LITERAL_SUFFIX,
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pedantic,
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"literals whose suffix is not separated by an underscore"
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}
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declare_clippy_lint! {
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/// **What it does:** Warns if an integral constant literal starts with `0`.
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///
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/// **Why is this bad?** In some languages (including the infamous C language
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/// and most of its
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/// family), this marks an octal constant. In Rust however, this is a decimal
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/// constant. This could
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/// be confusing for both the writer and a reader of the constant.
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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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/// In Rust:
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/// ```rust
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/// fn main() {
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/// let a = 0123;
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/// println!("{}", a);
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/// }
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/// ```
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///
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/// prints `123`, while in C:
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///
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/// ```c
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/// #include <stdio.h>
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///
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/// int main() {
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/// int a = 0123;
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/// printf("%d\n", a);
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/// }
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/// ```
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///
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/// prints `83` (as `83 == 0o123` while `123 == 0o173`).
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pub ZERO_PREFIXED_LITERAL,
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complexity,
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"integer literals starting with `0`"
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}
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declare_clippy_lint! {
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/// **What it does:** Warns if a generic shadows a built-in type.
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///
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/// **Why is this bad?** This gives surprising type errors.
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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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/// ```ignore
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/// impl<u32> Foo<u32> {
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/// fn impl_func(&self) -> u32 {
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/// 42
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/// }
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/// }
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/// ```
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pub BUILTIN_TYPE_SHADOW,
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style,
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"shadowing a builtin type"
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}
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declare_clippy_lint! {
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/// **What it does:** Checks for patterns in the form `name @ _`.
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///
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/// **Why is this bad?** It's almost always more readable to just use direct
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/// bindings.
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///
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/// **Known problems:** None.
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///
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/// **Example:**
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/// ```rust
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/// # let v = Some("abc");
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///
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/// match v {
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/// Some(x) => (),
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/// y @ _ => (), // easier written as `y`,
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/// }
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/// ```
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pub REDUNDANT_PATTERN,
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style,
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"using `name @ _` in a pattern"
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}
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declare_clippy_lint! {
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/// **What it does:** Checks for tuple patterns with a wildcard
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/// pattern (`_`) is next to a rest pattern (`..`).
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///
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/// _NOTE_: While `_, ..` means there is at least one element left, `..`
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/// means there are 0 or more elements left. This can make a difference
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/// when refactoring, but shouldn't result in errors in the refactored code,
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/// since the wildcard pattern isn't used anyway.
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/// **Why is this bad?** The wildcard pattern is unneeded as the rest pattern
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/// can match that element as well.
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///
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/// **Known problems:** None.
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///
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/// **Example:**
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/// ```rust
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/// # struct TupleStruct(u32, u32, u32);
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/// # let t = TupleStruct(1, 2, 3);
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///
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/// match t {
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/// TupleStruct(0, .., _) => (),
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/// _ => (),
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/// }
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/// ```
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/// can be written as
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/// ```rust
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/// # struct TupleStruct(u32, u32, u32);
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/// # let t = TupleStruct(1, 2, 3);
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///
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/// match t {
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/// TupleStruct(0, ..) => (),
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/// _ => (),
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/// }
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/// ```
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pub UNNEEDED_WILDCARD_PATTERN,
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complexity,
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"tuple patterns with a wildcard pattern (`_`) is next to a rest pattern (`..`)"
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}
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declare_lint_pass!(MiscEarlyLints => [
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UNNEEDED_FIELD_PATTERN,
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DUPLICATE_UNDERSCORE_ARGUMENT,
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REDUNDANT_CLOSURE_CALL,
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DOUBLE_NEG,
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MIXED_CASE_HEX_LITERALS,
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UNSEPARATED_LITERAL_SUFFIX,
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ZERO_PREFIXED_LITERAL,
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BUILTIN_TYPE_SHADOW,
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REDUNDANT_PATTERN,
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UNNEEDED_WILDCARD_PATTERN,
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]);
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// Used to find `return` statements or equivalents e.g., `?`
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struct ReturnVisitor {
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found_return: bool,
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}
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impl ReturnVisitor {
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#[must_use]
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fn new() -> Self {
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Self { found_return: false }
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}
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}
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impl<'ast> Visitor<'ast> for ReturnVisitor {
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fn visit_expr(&mut self, ex: &'ast Expr) {
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if let ExprKind::Ret(_) = ex.kind {
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self.found_return = true;
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} else if let ExprKind::Try(_) = ex.kind {
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self.found_return = true;
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}
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walk_expr(self, ex)
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}
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}
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impl EarlyLintPass for MiscEarlyLints {
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fn check_generics(&mut self, cx: &EarlyContext<'_>, gen: &Generics) {
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for param in &gen.params {
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if let GenericParamKind::Type { .. } = param.kind {
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let name = param.ident.as_str();
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if constants::BUILTIN_TYPES.contains(&&*name) {
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span_lint(
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cx,
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BUILTIN_TYPE_SHADOW,
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param.ident.span,
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&format!("This generic shadows the built-in type `{}`", name),
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);
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}
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}
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}
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}
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fn check_pat(&mut self, cx: &EarlyContext<'_>, pat: &Pat) {
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if let PatKind::Struct(ref npat, ref pfields, _) = pat.kind {
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let mut wilds = 0;
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let type_name = npat
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.segments
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.last()
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.expect("A path must have at least one segment")
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.ident
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.name;
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for field in pfields {
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if let PatKind::Wild = field.pat.kind {
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wilds += 1;
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}
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}
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if !pfields.is_empty() && wilds == pfields.len() {
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span_lint_and_help(
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cx,
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UNNEEDED_FIELD_PATTERN,
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pat.span,
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"All the struct fields are matched to a wildcard pattern, consider using `..`.",
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&format!("Try with `{} {{ .. }}` instead", type_name),
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);
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return;
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}
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if wilds > 0 {
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for field in pfields {
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if let PatKind::Wild = field.pat.kind {
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wilds -= 1;
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if wilds > 0 {
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span_lint(
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cx,
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UNNEEDED_FIELD_PATTERN,
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field.span,
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"You matched a field with a wildcard pattern. Consider using `..` instead",
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);
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} else {
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let mut normal = vec![];
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for field in pfields {
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match field.pat.kind {
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PatKind::Wild => {},
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_ => {
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if let Ok(n) = cx.sess().source_map().span_to_snippet(field.span) {
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normal.push(n);
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}
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},
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}
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}
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span_lint_and_help(
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cx,
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UNNEEDED_FIELD_PATTERN,
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field.span,
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"You matched a field with a wildcard pattern. Consider using `..` \
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instead",
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&format!("Try with `{} {{ {}, .. }}`", type_name, normal[..].join(", ")),
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);
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}
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}
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}
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}
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}
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if let PatKind::Ident(left, ident, Some(ref right)) = pat.kind {
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let left_binding = match left {
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BindingMode::ByRef(Mutability::Mut) => "ref mut ",
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BindingMode::ByRef(Mutability::Not) => "ref ",
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_ => "",
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};
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if let PatKind::Wild = right.kind {
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span_lint_and_sugg(
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cx,
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REDUNDANT_PATTERN,
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pat.span,
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&format!(
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"the `{} @ _` pattern can be written as just `{}`",
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ident.name, ident.name,
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),
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"try",
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format!("{}{}", left_binding, ident.name),
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Applicability::MachineApplicable,
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);
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}
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}
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check_unneeded_wildcard_pattern(cx, pat);
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}
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fn check_fn(&mut self, cx: &EarlyContext<'_>, fn_kind: FnKind<'_>, _: Span, _: NodeId) {
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let mut registered_names: FxHashMap<String, Span> = FxHashMap::default();
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for arg in &fn_kind.decl().inputs {
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if let PatKind::Ident(_, ident, None) = arg.pat.kind {
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let arg_name = ident.to_string();
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if arg_name.starts_with('_') {
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if let Some(correspondence) = registered_names.get(&arg_name[1..]) {
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span_lint(
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cx,
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DUPLICATE_UNDERSCORE_ARGUMENT,
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*correspondence,
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&format!(
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"`{}` already exists, having another argument having almost the same \
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name makes code comprehension and documentation more difficult",
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arg_name[1..].to_owned()
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),
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);
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}
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} else {
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registered_names.insert(arg_name, arg.pat.span);
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}
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}
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}
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}
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fn check_expr(&mut self, cx: &EarlyContext<'_>, expr: &Expr) {
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if in_external_macro(cx.sess(), expr.span) {
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return;
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}
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match expr.kind {
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ExprKind::Call(ref paren, _) => {
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if let ExprKind::Paren(ref closure) = paren.kind {
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if let ExprKind::Closure(_, _, _, ref decl, ref block, _) = closure.kind {
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let mut visitor = ReturnVisitor::new();
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visitor.visit_expr(block);
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if !visitor.found_return {
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span_lint_and_then(
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cx,
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REDUNDANT_CLOSURE_CALL,
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expr.span,
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"Try not to call a closure in the expression where it is declared.",
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|db| {
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if decl.inputs.is_empty() {
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let mut app = Applicability::MachineApplicable;
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let hint =
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snippet_with_applicability(cx, block.span, "..", &mut app).into_owned();
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db.span_suggestion(expr.span, "Try doing something like: ", hint, app);
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}
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},
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);
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}
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}
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}
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},
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ExprKind::Unary(UnOp::Neg, ref inner) => {
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if let ExprKind::Unary(UnOp::Neg, _) = inner.kind {
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span_lint(
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cx,
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DOUBLE_NEG,
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expr.span,
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"`--x` could be misinterpreted as pre-decrement by C programmers, is usually a no-op",
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);
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}
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},
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ExprKind::Lit(ref lit) => Self::check_lit(cx, lit),
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_ => (),
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}
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}
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fn check_block(&mut self, cx: &EarlyContext<'_>, block: &Block) {
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for w in block.stmts.windows(2) {
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if_chain! {
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if let StmtKind::Local(ref local) = w[0].kind;
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if let Option::Some(ref t) = local.init;
|
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if let ExprKind::Closure(..) = t.kind;
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if let PatKind::Ident(_, ident, _) = local.pat.kind;
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if let StmtKind::Semi(ref second) = w[1].kind;
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if let ExprKind::Assign(_, ref call, _) = second.kind;
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if let ExprKind::Call(ref closure, _) = call.kind;
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if let ExprKind::Path(_, ref path) = closure.kind;
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then {
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if ident == path.segments[0].ident {
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span_lint(
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cx,
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REDUNDANT_CLOSURE_CALL,
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second.span,
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"Closure called just once immediately after it was declared",
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);
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}
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}
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}
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}
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}
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}
|
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impl MiscEarlyLints {
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fn check_lit(cx: &EarlyContext<'_>, lit: &Lit) {
|
|
// We test if first character in snippet is a number, because the snippet could be an expansion
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|
// from a built-in macro like `line!()` or a proc-macro like `#[wasm_bindgen]`.
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// Note that this check also covers special case that `line!()` is eagerly expanded by compiler.
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// See <https://github.com/rust-lang/rust-clippy/issues/4507> for a regression.
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// FIXME: Find a better way to detect those cases.
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let lit_snip = match snippet_opt(cx, lit.span) {
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Some(snip) if snip.chars().next().map_or(false, |c| c.is_digit(10)) => snip,
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_ => return,
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};
|
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|
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if let LitKind::Int(value, lit_int_type) = lit.kind {
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let suffix = match lit_int_type {
|
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LitIntType::Signed(ty) => ty.name_str(),
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LitIntType::Unsigned(ty) => ty.name_str(),
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LitIntType::Unsuffixed => "",
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};
|
|
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let maybe_last_sep_idx = if let Some(val) = lit_snip.len().checked_sub(suffix.len() + 1) {
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val
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} else {
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return; // It's useless so shouldn't lint.
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};
|
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// Do not lint when literal is unsuffixed.
|
|
if !suffix.is_empty() && lit_snip.as_bytes()[maybe_last_sep_idx] != b'_' {
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span_lint_and_sugg(
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cx,
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UNSEPARATED_LITERAL_SUFFIX,
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|
lit.span,
|
|
"integer type suffix should be separated by an underscore",
|
|
"add an underscore",
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|
format!("{}_{}", &lit_snip[..=maybe_last_sep_idx], suffix),
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Applicability::MachineApplicable,
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);
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}
|
|
|
|
if lit_snip.starts_with("0x") {
|
|
if maybe_last_sep_idx <= 2 {
|
|
// It's meaningless or causes range error.
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return;
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}
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|
let mut seen = (false, false);
|
|
for ch in lit_snip.as_bytes()[2..=maybe_last_sep_idx].iter() {
|
|
match ch {
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|
b'a'..=b'f' => seen.0 = true,
|
|
b'A'..=b'F' => seen.1 = true,
|
|
_ => {},
|
|
}
|
|
if seen.0 && seen.1 {
|
|
span_lint(
|
|
cx,
|
|
MIXED_CASE_HEX_LITERALS,
|
|
lit.span,
|
|
"inconsistent casing in hexadecimal literal",
|
|
);
|
|
break;
|
|
}
|
|
}
|
|
} else if lit_snip.starts_with("0b") || lit_snip.starts_with("0o") {
|
|
/* nothing to do */
|
|
} else if value != 0 && lit_snip.starts_with('0') {
|
|
span_lint_and_then(
|
|
cx,
|
|
ZERO_PREFIXED_LITERAL,
|
|
lit.span,
|
|
"this is a decimal constant",
|
|
|db| {
|
|
db.span_suggestion(
|
|
lit.span,
|
|
"if you mean to use a decimal constant, remove the `0` to avoid confusion",
|
|
lit_snip.trim_start_matches(|c| c == '_' || c == '0').to_string(),
|
|
Applicability::MaybeIncorrect,
|
|
);
|
|
db.span_suggestion(
|
|
lit.span,
|
|
"if you mean to use an octal constant, use `0o`",
|
|
format!("0o{}", lit_snip.trim_start_matches(|c| c == '_' || c == '0')),
|
|
Applicability::MaybeIncorrect,
|
|
);
|
|
},
|
|
);
|
|
}
|
|
} else if let LitKind::Float(_, LitFloatType::Suffixed(float_ty)) = lit.kind {
|
|
let suffix = float_ty.name_str();
|
|
let maybe_last_sep_idx = if let Some(val) = lit_snip.len().checked_sub(suffix.len() + 1) {
|
|
val
|
|
} else {
|
|
return; // It's useless so shouldn't lint.
|
|
};
|
|
if lit_snip.as_bytes()[maybe_last_sep_idx] != b'_' {
|
|
span_lint_and_sugg(
|
|
cx,
|
|
UNSEPARATED_LITERAL_SUFFIX,
|
|
lit.span,
|
|
"float type suffix should be separated by an underscore",
|
|
"add an underscore",
|
|
format!("{}_{}", &lit_snip[..=maybe_last_sep_idx], suffix),
|
|
Applicability::MachineApplicable,
|
|
);
|
|
}
|
|
}
|
|
}
|
|
}
|
|
|
|
fn check_unneeded_wildcard_pattern(cx: &EarlyContext<'_>, pat: &Pat) {
|
|
if let PatKind::TupleStruct(_, ref patterns) | PatKind::Tuple(ref patterns) = pat.kind {
|
|
fn span_lint(cx: &EarlyContext<'_>, span: Span, only_one: bool) {
|
|
span_lint_and_sugg(
|
|
cx,
|
|
UNNEEDED_WILDCARD_PATTERN,
|
|
span,
|
|
if only_one {
|
|
"this pattern is unneeded as the `..` pattern can match that element"
|
|
} else {
|
|
"these patterns are unneeded as the `..` pattern can match those elements"
|
|
},
|
|
if only_one { "remove it" } else { "remove them" },
|
|
"".to_string(),
|
|
Applicability::MachineApplicable,
|
|
);
|
|
}
|
|
|
|
#[allow(clippy::trivially_copy_pass_by_ref)]
|
|
fn is_wild<P: std::ops::Deref<Target = Pat>>(pat: &&P) -> bool {
|
|
if let PatKind::Wild = pat.kind {
|
|
true
|
|
} else {
|
|
false
|
|
}
|
|
}
|
|
|
|
if let Some(rest_index) = patterns.iter().position(|pat| pat.is_rest()) {
|
|
if let Some((left_index, left_pat)) = patterns[..rest_index]
|
|
.iter()
|
|
.rev()
|
|
.take_while(is_wild)
|
|
.enumerate()
|
|
.last()
|
|
{
|
|
span_lint(cx, left_pat.span.until(patterns[rest_index].span), left_index == 0);
|
|
}
|
|
|
|
if let Some((right_index, right_pat)) =
|
|
patterns[rest_index + 1..].iter().take_while(is_wild).enumerate().last()
|
|
{
|
|
span_lint(
|
|
cx,
|
|
patterns[rest_index].span.shrink_to_hi().to(right_pat.span),
|
|
right_index == 0,
|
|
);
|
|
}
|
|
}
|
|
}
|
|
}
|