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Auto merge of #8761 - tamaroning:fix_8505, r=Jarcho
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`undocumented_unsafe_blocks` does not trigger on unsafe trait impls

Closes #8505

changelog: This lint checks unsafe impls NOT from macro expansions and checks ones in macro declarations.
~~`unsafe impl`s from macro invocations don't trigger the lint for now.~~
~~This lint checks unsafe impls from/not from macro expansions~~
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@bors
bors committed May 16, 2022
2 parents 6ec7359 + 9e66f2d commit a1632ff
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Showing 3 changed files with 437 additions and 30 deletions.
196 changes: 168 additions & 28 deletions clippy_lints/src/undocumented_unsafe_blocks.rs
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Original file line number Diff line number Diff line change
@@ -1,17 +1,18 @@
use clippy_utils::diagnostics::span_lint_and_help;
use clippy_utils::is_lint_allowed;
use clippy_utils::source::walk_span_to_context;
use clippy_utils::{get_parent_node, is_lint_allowed};
use rustc_data_structures::sync::Lrc;
use rustc_hir::{Block, BlockCheckMode, UnsafeSource};
use rustc_hir as hir;
use rustc_hir::{Block, BlockCheckMode, ItemKind, Node, UnsafeSource};
use rustc_lexer::{tokenize, TokenKind};
use rustc_lint::{LateContext, LateLintPass, LintContext};
use rustc_middle::lint::in_external_macro;
use rustc_session::{declare_lint_pass, declare_tool_lint};
use rustc_span::{BytePos, Pos, SyntaxContext};
use rustc_span::{BytePos, Pos, Span, SyntaxContext};

declare_clippy_lint! {
/// ### What it does
/// Checks for `unsafe` blocks without a `// SAFETY: ` comment
/// Checks for `unsafe` blocks and impls without a `// SAFETY: ` comment
/// explaining why the unsafe operations performed inside
/// the block are safe.
///
Expand All @@ -34,7 +35,7 @@ declare_clippy_lint! {
/// ```
///
/// ### Why is this bad?
/// Undocumented unsafe blocks can make it difficult to
/// Undocumented unsafe blocks and impls can make it difficult to
/// read and maintain code, as well as uncover unsoundness
/// and bugs.
///
Expand Down Expand Up @@ -66,7 +67,7 @@ impl LateLintPass<'_> for UndocumentedUnsafeBlocks {
if block.rules == BlockCheckMode::UnsafeBlock(UnsafeSource::UserProvided)
&& !in_external_macro(cx.tcx.sess, block.span)
&& !is_lint_allowed(cx, UNDOCUMENTED_UNSAFE_BLOCKS, block.hir_id)
&& !is_unsafe_from_proc_macro(cx, block)
&& !is_unsafe_from_proc_macro(cx, block.span)
&& !block_has_safety_comment(cx, block)
{
let source_map = cx.tcx.sess.source_map();
Expand All @@ -86,11 +87,37 @@ impl LateLintPass<'_> for UndocumentedUnsafeBlocks {
);
}
}

fn check_item(&mut self, cx: &LateContext<'_>, item: &hir::Item<'_>) {
if let hir::ItemKind::Impl(imple) = item.kind
&& imple.unsafety == hir::Unsafety::Unsafe
&& !in_external_macro(cx.tcx.sess, item.span)
&& !is_lint_allowed(cx, UNDOCUMENTED_UNSAFE_BLOCKS, item.hir_id())
&& !is_unsafe_from_proc_macro(cx, item.span)
&& !item_has_safety_comment(cx, item)
{
let source_map = cx.tcx.sess.source_map();
let span = if source_map.is_multiline(item.span) {
source_map.span_until_char(item.span, '\n')
} else {
item.span
};

span_lint_and_help(
cx,
UNDOCUMENTED_UNSAFE_BLOCKS,
span,
"unsafe impl missing a safety comment",
None,
"consider adding a safety comment on the preceding line",
);
}
}
}

fn is_unsafe_from_proc_macro(cx: &LateContext<'_>, block: &Block<'_>) -> bool {
fn is_unsafe_from_proc_macro(cx: &LateContext<'_>, span: Span) -> bool {
let source_map = cx.sess().source_map();
let file_pos = source_map.lookup_byte_offset(block.span.lo());
let file_pos = source_map.lookup_byte_offset(span.lo());
file_pos
.sf
.src
Expand All @@ -100,7 +127,7 @@ fn is_unsafe_from_proc_macro(cx: &LateContext<'_>, block: &Block<'_>) -> bool {
}

/// Checks if the lines immediately preceding the block contain a safety comment.
fn block_has_safety_comment(cx: &LateContext<'_>, block: &Block<'_>) -> bool {
fn block_has_safety_comment(cx: &LateContext<'_>, block: &hir::Block<'_>) -> bool {
// This intentionally ignores text before the start of a function so something like:
// ```
// // SAFETY: reason
Expand All @@ -109,13 +136,115 @@ fn block_has_safety_comment(cx: &LateContext<'_>, block: &Block<'_>) -> bool {
// won't work. This is to avoid dealing with where such a comment should be place relative to
// attributes and doc comments.

span_from_macro_expansion_has_safety_comment(cx, block.span) || span_in_body_has_safety_comment(cx, block.span)
}

/// Checks if the lines immediately preceding the item contain a safety comment.
#[allow(clippy::collapsible_match)]
fn item_has_safety_comment(cx: &LateContext<'_>, item: &hir::Item<'_>) -> bool {
if span_from_macro_expansion_has_safety_comment(cx, item.span) {
return true;
}

if item.span.ctxt() == SyntaxContext::root() {
if let Some(parent_node) = get_parent_node(cx.tcx, item.hir_id()) {
let comment_start = match parent_node {
Node::Crate(parent_mod) => {
comment_start_before_impl_in_mod(cx, parent_mod, parent_mod.spans.inner_span, item)
},
Node::Item(parent_item) => {
if let ItemKind::Mod(parent_mod) = &parent_item.kind {
comment_start_before_impl_in_mod(cx, parent_mod, parent_item.span, item)
} else {
// Doesn't support impls in this position. Pretend a comment was found.
return true;
}
},
Node::Stmt(stmt) => {
if let Some(stmt_parent) = get_parent_node(cx.tcx, stmt.hir_id) {
match stmt_parent {
Node::Block(block) => walk_span_to_context(block.span, SyntaxContext::root()).map(Span::lo),
_ => {
// Doesn't support impls in this position. Pretend a comment was found.
return true;
},
}
} else {
// Problem getting the parent node. Pretend a comment was found.
return true;
}
},
_ => {
// Doesn't support impls in this position. Pretend a comment was found.
return true;
},
};

let source_map = cx.sess().source_map();
if let Some(comment_start) = comment_start
&& let Ok(unsafe_line) = source_map.lookup_line(item.span.lo())
&& let Ok(comment_start_line) = source_map.lookup_line(comment_start)
&& Lrc::ptr_eq(&unsafe_line.sf, &comment_start_line.sf)
&& let Some(src) = unsafe_line.sf.src.as_deref()
{
comment_start_line.line < unsafe_line.line && text_has_safety_comment(
src,
&unsafe_line.sf.lines[comment_start_line.line + 1..=unsafe_line.line],
unsafe_line.sf.start_pos.to_usize(),
)
} else {
// Problem getting source text. Pretend a comment was found.
true
}
} else {
// No parent node. Pretend a comment was found.
true
}
} else {
false
}
}

fn comment_start_before_impl_in_mod(
cx: &LateContext<'_>,
parent_mod: &hir::Mod<'_>,
parent_mod_span: Span,
imple: &hir::Item<'_>,
) -> Option<BytePos> {
parent_mod.item_ids.iter().enumerate().find_map(|(idx, item_id)| {
if *item_id == imple.item_id() {
if idx == 0 {
// mod A { /* comment */ unsafe impl T {} ... }
// ^------------------------------------------^ returns the start of this span
// ^---------------------^ finally checks comments in this range
if let Some(sp) = walk_span_to_context(parent_mod_span, SyntaxContext::root()) {
return Some(sp.lo());
}
} else {
// some_item /* comment */ unsafe impl T {}
// ^-------^ returns the end of this span
// ^---------------^ finally checks comments in this range
let prev_item = cx.tcx.hir().item(parent_mod.item_ids[idx - 1]);
if let Some(sp) = walk_span_to_context(prev_item.span, SyntaxContext::root()) {
return Some(sp.hi());
}
}
}
None
})
}

fn span_from_macro_expansion_has_safety_comment(cx: &LateContext<'_>, span: Span) -> bool {
let source_map = cx.sess().source_map();
let ctxt = block.span.ctxt();
if ctxt != SyntaxContext::root() {
// From a macro expansion. Get the text from the start of the macro declaration to start of the unsafe block.
let ctxt = span.ctxt();
if ctxt == SyntaxContext::root() {
false
} else {
// From a macro expansion. Get the text from the start of the macro declaration to start of the
// unsafe block.
// macro_rules! foo { () => { stuff }; (x) => { unsafe { stuff } }; }
// ^--------------------------------------------^
if let Ok(unsafe_line) = source_map.lookup_line(block.span.lo())
if let Ok(unsafe_line) = source_map.lookup_line(span.lo())
&& let Ok(macro_line) = source_map.lookup_line(ctxt.outer_expn_data().def_site.lo())
&& Lrc::ptr_eq(&unsafe_line.sf, &macro_line.sf)
&& let Some(src) = unsafe_line.sf.src.as_deref()
Expand All @@ -129,24 +258,35 @@ fn block_has_safety_comment(cx: &LateContext<'_>, block: &Block<'_>) -> bool {
// Problem getting source text. Pretend a comment was found.
true
}
} else if let Ok(unsafe_line) = source_map.lookup_line(block.span.lo())
}
}

fn span_in_body_has_safety_comment(cx: &LateContext<'_>, span: Span) -> bool {
let source_map = cx.sess().source_map();
let ctxt = span.ctxt();
if ctxt == SyntaxContext::root()
&& let Some(body) = cx.enclosing_body
&& let Some(body_span) = walk_span_to_context(cx.tcx.hir().body(body).value.span, SyntaxContext::root())
&& let Ok(body_line) = source_map.lookup_line(body_span.lo())
&& Lrc::ptr_eq(&unsafe_line.sf, &body_line.sf)
&& let Some(src) = unsafe_line.sf.src.as_deref()
{
// Get the text from the start of function body to the unsafe block.
// fn foo() { some_stuff; unsafe { stuff }; other_stuff; }
// ^-------------^
body_line.line < unsafe_line.line && text_has_safety_comment(
src,
&unsafe_line.sf.lines[body_line.line + 1..=unsafe_line.line],
unsafe_line.sf.start_pos.to_usize(),
)
if let Ok(unsafe_line) = source_map.lookup_line(span.lo())
&& let Some(body_span) = walk_span_to_context(cx.tcx.hir().body(body).value.span, SyntaxContext::root())
&& let Ok(body_line) = source_map.lookup_line(body_span.lo())
&& Lrc::ptr_eq(&unsafe_line.sf, &body_line.sf)
&& let Some(src) = unsafe_line.sf.src.as_deref()
{
// Get the text from the start of function body to the unsafe block.
// fn foo() { some_stuff; unsafe { stuff }; other_stuff; }
// ^-------------^
body_line.line < unsafe_line.line && text_has_safety_comment(
src,
&unsafe_line.sf.lines[body_line.line + 1..=unsafe_line.line],
unsafe_line.sf.start_pos.to_usize(),
)
} else {
// Problem getting source text. Pretend a comment was found.
true
}
} else {
// Problem getting source text. Pretend a comment was found.
true
false
}
}

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