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rust-clippy/clippy_lints/src/functions.rs

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use crate::utils::{iter_input_pats, snippet, span_lint, type_is_unsafe_function};
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use matches::matches;
use rustc::hir;
use rustc::hir::def::Def;
use rustc::hir::intravisit;
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use rustc::lint::{in_external_macro, LateContext, LateLintPass, LintArray, LintContext, LintPass};
use rustc::ty;
use rustc::{declare_tool_lint, lint_array};
use rustc_data_structures::fx::FxHashSet;
use rustc_target::spec::abi::Abi;
use syntax::ast;
use syntax::source_map::Span;
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/// **What it does:** Checks for functions with too many parameters.
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///
/// **Why is this bad?** Functions with lots of parameters are considered bad
/// style and reduce readability (“what does the 5th parameter mean?”). Consider
/// grouping some parameters into a new type.
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///
/// **Known problems:** None.
///
/// **Example:**
/// ```rust
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/// fn foo(x: u32, y: u32, name: &str, c: Color, w: f32, h: f32, a: f32, b: f32) {
/// ..
/// }
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/// ```
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declare_clippy_lint! {
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pub TOO_MANY_ARGUMENTS,
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complexity,
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"functions with too many arguments"
}
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/// **What it does:** Checks for functions with a large amount of lines.
///
/// **Why is this bad?** Functions with a lot of lines are harder to understand
/// due to having to look at a larger amount of code to understand what the
/// function is doing. Consider splitting the body of the function into
/// multiple functions.
///
/// **Known problems:** None.
///
/// **Example:**
/// ``` rust
/// fn im_too_long() {
/// println!("");
/// // ... 100 more LoC
/// println!("");
/// }
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/// ```
declare_clippy_lint! {
pub TOO_MANY_LINES,
pedantic,
"functions with too many lines"
}
/// **What it does:** Checks for public functions that dereferences raw pointer
/// arguments but are not marked unsafe.
///
/// **Why is this bad?** The function should probably be marked `unsafe`, since
/// for an arbitrary raw pointer, there is no way of telling for sure if it is
/// valid.
///
/// **Known problems:**
///
/// * It does not check functions recursively so if the pointer is passed to a
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/// private non-`unsafe` function which does the dereferencing, the lint won't
/// trigger.
/// * It only checks for arguments whose type are raw pointers, not raw pointers
/// got from an argument in some other way (`fn foo(bar: &[*const u8])` or
/// `some_argument.get_raw_ptr()`).
///
/// **Example:**
/// ```rust
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/// pub fn foo(x: *const u8) {
/// println!("{}", unsafe { *x });
/// }
/// ```
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declare_clippy_lint! {
pub NOT_UNSAFE_PTR_ARG_DEREF,
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correctness,
"public functions dereferencing raw pointer arguments but not marked `unsafe`"
}
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#[derive(Copy, Clone)]
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pub struct Functions {
threshold: u64,
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max_lines: u64,
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}
impl Functions {
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pub fn new(threshold: u64, max_lines: u64) -> Self {
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Self { threshold, max_lines }
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}
}
impl LintPass for Functions {
fn get_lints(&self) -> LintArray {
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lint_array!(TOO_MANY_ARGUMENTS, TOO_MANY_LINES, NOT_UNSAFE_PTR_ARG_DEREF)
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}
fn name(&self) -> &'static str {
"Functions"
}
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}
impl<'a, 'tcx> LateLintPass<'a, 'tcx> for Functions {
fn check_fn(
&mut self,
cx: &LateContext<'a, 'tcx>,
kind: intravisit::FnKind<'tcx>,
decl: &'tcx hir::FnDecl,
body: &'tcx hir::Body,
span: Span,
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nodeid: ast::NodeId,
) {
let is_impl = if let Some(hir::Node::Item(item)) = cx.tcx.hir().find(cx.tcx.hir().get_parent_node(nodeid)) {
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matches!(item.node, hir::ItemKind::Impl(_, _, _, _, Some(_), _, _))
} else {
false
};
let unsafety = match kind {
hir::intravisit::FnKind::ItemFn(_, _, hir::FnHeader { unsafety, .. }, _, _) => unsafety,
hir::intravisit::FnKind::Method(_, sig, _, _) => sig.header.unsafety,
hir::intravisit::FnKind::Closure(_) => return,
};
// don't warn for implementations, it's not their fault
if !is_impl {
// don't lint extern functions decls, it's not their fault either
match kind {
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hir::intravisit::FnKind::Method(
_,
&hir::MethodSig {
header: hir::FnHeader { abi: Abi::Rust, .. },
..
},
_,
_,
)
| hir::intravisit::FnKind::ItemFn(_, _, hir::FnHeader { abi: Abi::Rust, .. }, _, _) => {
self.check_arg_number(cx, decl, span)
},
_ => {},
}
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}
self.check_raw_ptr(cx, unsafety, decl, body, nodeid);
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self.check_line_number(cx, span);
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}
fn check_trait_item(&mut self, cx: &LateContext<'a, 'tcx>, item: &'tcx hir::TraitItem) {
if let hir::TraitItemKind::Method(ref sig, ref eid) = item.node {
// don't lint extern functions decls, it's not their fault
if sig.header.abi == Abi::Rust {
self.check_arg_number(cx, &sig.decl, item.span);
}
if let hir::TraitMethod::Provided(eid) = *eid {
let body = cx.tcx.hir().body(eid);
self.check_raw_ptr(cx, sig.header.unsafety, &sig.decl, body, item.id);
}
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}
}
}
impl<'a, 'tcx> Functions {
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fn check_arg_number(self, cx: &LateContext<'_, '_>, decl: &hir::FnDecl, span: Span) {
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let args = decl.inputs.len() as u64;
if args > self.threshold {
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span_lint(
cx,
TOO_MANY_ARGUMENTS,
span,
&format!("this function has too many arguments ({}/{})", args, self.threshold),
);
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}
}
fn check_line_number(self, cx: &LateContext<'_, '_>, span: Span) {
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if in_external_macro(cx.sess(), span) {
return;
}
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let code_snippet = snippet(cx, span, "..");
let mut line_count: u64 = 0;
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let mut in_comment = false;
let mut code_in_line;
// Skip the surrounding function decl.
let start_brace_idx = match code_snippet.find('{') {
Some(i) => i + 1,
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None => 0,
};
let end_brace_idx = match code_snippet.find('}') {
Some(i) => i,
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None => code_snippet.len(),
};
let function_lines = code_snippet[start_brace_idx..end_brace_idx].lines();
for mut line in function_lines {
code_in_line = false;
loop {
line = line.trim_start();
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if line.is_empty() {
break;
}
if in_comment {
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match line.find("*/") {
Some(i) => {
line = &line[i + 2..];
in_comment = false;
continue;
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},
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None => break,
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}
} else {
let multi_idx = match line.find("/*") {
Some(i) => i,
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None => line.len(),
};
let single_idx = match line.find("//") {
Some(i) => i,
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None => line.len(),
};
code_in_line |= multi_idx > 0 && single_idx > 0;
// Implies multi_idx is below line.len()
if multi_idx < single_idx {
line = &line[multi_idx + 2..];
in_comment = true;
continue;
}
break;
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}
}
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if code_in_line {
line_count += 1;
}
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}
if line_count > self.max_lines {
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span_lint(cx, TOO_MANY_LINES, span, "This function has a large number of lines.")
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}
}
fn check_raw_ptr(
self,
cx: &LateContext<'a, 'tcx>,
unsafety: hir::Unsafety,
decl: &'tcx hir::FnDecl,
body: &'tcx hir::Body,
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nodeid: ast::NodeId,
) {
let expr = &body.value;
if unsafety == hir::Unsafety::Normal && cx.access_levels.is_exported(nodeid) {
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let raw_ptrs = iter_input_pats(decl, body)
.zip(decl.inputs.iter())
.filter_map(|(arg, ty)| raw_ptr_arg(arg, ty))
.collect::<FxHashSet<_>>();
if !raw_ptrs.is_empty() {
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let tables = cx.tcx.body_tables(body.id());
let mut v = DerefVisitor {
cx,
ptrs: raw_ptrs,
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tables,
};
hir::intravisit::walk_expr(&mut v, expr);
}
}
}
}
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fn raw_ptr_arg(arg: &hir::Arg, ty: &hir::Ty) -> Option<ast::NodeId> {
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if let (&hir::PatKind::Binding(_, id, _, _), &hir::TyKind::Ptr(_)) = (&arg.pat.node, &ty.node) {
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Some(id)
} else {
None
}
}
struct DerefVisitor<'a, 'tcx: 'a> {
cx: &'a LateContext<'a, 'tcx>,
ptrs: FxHashSet<ast::NodeId>,
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tables: &'a ty::TypeckTables<'tcx>,
}
impl<'a, 'tcx> hir::intravisit::Visitor<'tcx> for DerefVisitor<'a, 'tcx> {
fn visit_expr(&mut self, expr: &'tcx hir::Expr) {
match expr.node {
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hir::ExprKind::Call(ref f, ref args) => {
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let ty = self.tables.expr_ty(f);
if type_is_unsafe_function(self.cx, ty) {
for arg in args {
self.check_arg(arg);
}
}
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},
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hir::ExprKind::MethodCall(_, _, ref args) => {
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let def_id = self.tables.type_dependent_defs()[expr.hir_id].def_id();
let base_type = self.cx.tcx.type_of(def_id);
if type_is_unsafe_function(self.cx, base_type) {
for arg in args {
self.check_arg(arg);
}
}
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},
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hir::ExprKind::Unary(hir::UnDeref, ref ptr) => self.check_arg(ptr),
_ => (),
}
hir::intravisit::walk_expr(self, expr);
}
fn nested_visit_map<'this>(&'this mut self) -> intravisit::NestedVisitorMap<'this, 'tcx> {
intravisit::NestedVisitorMap::None
}
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}
impl<'a, 'tcx: 'a> DerefVisitor<'a, 'tcx> {
fn check_arg(&self, ptr: &hir::Expr) {
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if let hir::ExprKind::Path(ref qpath) = ptr.node {
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if let Def::Local(id) = self.cx.tables.qpath_def(qpath, ptr.hir_id) {
if self.ptrs.contains(&id) {
span_lint(
self.cx,
NOT_UNSAFE_PTR_ARG_DEREF,
ptr.span,
"this public function dereferences a raw pointer but is not marked `unsafe`",
);
}
}
}
}
}