Don't lint undocumented_unsafe_blocks on bad proc-macro spans.

clippy_lints/src/undocumented_unsafe_blocks.rs

@@ -48,6 +48,7 @@ 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)
             && !block_has_safety_comment(cx, block)
         {
             let source_map = cx.tcx.sess.source_map();
@@ -69,6 +70,17 @@ impl LateLintPass<'_> for UndocumentedUnsafeBlocks {
     }
 }
 
+fn is_unsafe_from_proc_macro(cx: &LateContext<'_>, block: &Block<'_>) -> bool {
+    let source_map = cx.sess().source_map();
+    let file_pos = source_map.lookup_byte_offset(block.span.lo());
+    file_pos
+        .sf
+        .src
+        .as_deref()
+        .and_then(|src| src.get(file_pos.pos.to_usize()..))
+        .map_or(true, |src| !src.starts_with("unsafe"))
+}
+
 /// Checks if the lines immediately preceding the block contain a safety comment.
 fn block_has_safety_comment(cx: &LateContext<'_>, block: &Block<'_>) -> bool {
     // This intentionally ignores text before the start of a function so something like:

tests/ui/auxiliary/proc_macro_unsafe.rs

@@ -0,0 +1,18 @@
+// compile-flags: --emit=link
+// no-prefer-dynamic
+
+#![crate_type = "proc-macro"]
+
+extern crate proc_macro;
+
+use proc_macro::{Delimiter, Group, Ident, TokenStream, TokenTree};
+
+#[proc_macro]
+pub fn unsafe_block(input: TokenStream) -> TokenStream {
+    let span = input.into_iter().next().unwrap().span();
+    TokenStream::from_iter([TokenTree::Ident(Ident::new("unsafe", span)), {
+        let mut group = Group::new(Delimiter::Brace, TokenStream::new());
+        group.set_span(span);
+        TokenTree::Group(group)
+    }])
+}

tests/ui/undocumented_unsafe_blocks.rs

@@ -1,5 +1,9 @@
+// aux-build:proc_macro_unsafe.rs
+
 #![warn(clippy::undocumented_unsafe_blocks)]
 
+extern crate proc_macro_unsafe;
+
 // Valid comments
 
 fn nested_local() {
@@ -241,6 +245,10 @@ fn in_multiline_macro_call(x: *const u32) {
     );
 }
 
+fn from_proc_macro() {
+    proc_macro_unsafe::unsafe_block!(token);
+}
+
 // Invalid comments
 
 fn no_comment() {

tests/ui/undocumented_unsafe_blocks.stderr

@@ -1,5 +1,5 @@
 error: unsafe block missing a safety comment
-  --> $DIR/undocumented_unsafe_blocks.rs:247:5
+  --> $DIR/undocumented_unsafe_blocks.rs:255:5
    |
 LL |     unsafe {}
    |     ^^^^^^^^^
@@ -8,95 +8,95 @@ LL |     unsafe {}
    = help: consider adding a safety comment on the preceding line
 
 error: unsafe block missing a safety comment
-  --> $DIR/undocumented_unsafe_blocks.rs:251:14
+  --> $DIR/undocumented_unsafe_blocks.rs:259:14
    |
 LL |     let _ = [unsafe { 14 }, unsafe { 15 }, 42, unsafe { 16 }];
    |              ^^^^^^^^^^^^^
    |
    = help: consider adding a safety comment on the preceding line
 
 error: unsafe block missing a safety comment
-  --> $DIR/undocumented_unsafe_blocks.rs:251:29
+  --> $DIR/undocumented_unsafe_blocks.rs:259:29
    |
 LL |     let _ = [unsafe { 14 }, unsafe { 15 }, 42, unsafe { 16 }];
    |                             ^^^^^^^^^^^^^
    |
    = help: consider adding a safety comment on the preceding line
 
 error: unsafe block missing a safety comment
-  --> $DIR/undocumented_unsafe_blocks.rs:251:48
+  --> $DIR/undocumented_unsafe_blocks.rs:259:48
    |
 LL |     let _ = [unsafe { 14 }, unsafe { 15 }, 42, unsafe { 16 }];
    |                                                ^^^^^^^^^^^^^
    |
    = help: consider adding a safety comment on the preceding line
 
 error: unsafe block missing a safety comment
-  --> $DIR/undocumented_unsafe_blocks.rs:255:18
+  --> $DIR/undocumented_unsafe_blocks.rs:263:18
    |
 LL |     let _ = (42, unsafe {}, "test", unsafe {});
    |                  ^^^^^^^^^
    |
    = help: consider adding a safety comment on the preceding line
 
 error: unsafe block missing a safety comment
-  --> $DIR/undocumented_unsafe_blocks.rs:255:37
+  --> $DIR/undocumented_unsafe_blocks.rs:263:37
    |
 LL |     let _ = (42, unsafe {}, "test", unsafe {});
    |                                     ^^^^^^^^^
    |
    = help: consider adding a safety comment on the preceding line
 
 error: unsafe block missing a safety comment
-  --> $DIR/undocumented_unsafe_blocks.rs:259:14
+  --> $DIR/undocumented_unsafe_blocks.rs:267:14
    |
 LL |     let _ = *unsafe { &42 };
    |              ^^^^^^^^^^^^^^
    |
    = help: consider adding a safety comment on the preceding line
 
 error: unsafe block missing a safety comment
-  --> $DIR/undocumented_unsafe_blocks.rs:264:19
+  --> $DIR/undocumented_unsafe_blocks.rs:272:19
    |
 LL |     let _ = match unsafe {} {
    |                   ^^^^^^^^^
    |
    = help: consider adding a safety comment on the preceding line
 
 error: unsafe block missing a safety comment
-  --> $DIR/undocumented_unsafe_blocks.rs:270:14
+  --> $DIR/undocumented_unsafe_blocks.rs:278:14
    |
 LL |     let _ = &unsafe {};
    |              ^^^^^^^^^
    |
    = help: consider adding a safety comment on the preceding line
 
 error: unsafe block missing a safety comment
-  --> $DIR/undocumented_unsafe_blocks.rs:274:14
+  --> $DIR/undocumented_unsafe_blocks.rs:282:14
    |
 LL |     let _ = [unsafe {}; 5];
    |              ^^^^^^^^^
    |
    = help: consider adding a safety comment on the preceding line
 
 error: unsafe block missing a safety comment
-  --> $DIR/undocumented_unsafe_blocks.rs:278:13
+  --> $DIR/undocumented_unsafe_blocks.rs:286:13
    |
 LL |     let _ = unsafe {};
    |             ^^^^^^^^^
    |
    = help: consider adding a safety comment on the preceding line
 
 error: unsafe block missing a safety comment
-  --> $DIR/undocumented_unsafe_blocks.rs:288:8
+  --> $DIR/undocumented_unsafe_blocks.rs:296:8
    |
 LL |     t!(unsafe {});
    |        ^^^^^^^^^
    |
    = help: consider adding a safety comment on the preceding line
 
 error: unsafe block missing a safety comment
-  --> $DIR/undocumented_unsafe_blocks.rs:294:13
+  --> $DIR/undocumented_unsafe_blocks.rs:302:13
    |
 LL |             unsafe {}
    |             ^^^^^^^^^
@@ -108,31 +108,31 @@ LL |     t!();
    = note: this error originates in the macro `t` (in Nightly builds, run with -Z macro-backtrace for more info)
 
 error: unsafe block missing a safety comment
-  --> $DIR/undocumented_unsafe_blocks.rs:302:5
+  --> $DIR/undocumented_unsafe_blocks.rs:310:5
    |
 LL |     unsafe {} // SAFETY:
    |     ^^^^^^^^^
    |
    = help: consider adding a safety comment on the preceding line
 
 error: unsafe block missing a safety comment
-  --> $DIR/undocumented_unsafe_blocks.rs:306:5
+  --> $DIR/undocumented_unsafe_blocks.rs:314:5
    |
 LL |     unsafe {
    |     ^^^^^^^^
    |
    = help: consider adding a safety comment on the preceding line
 
 error: unsafe block missing a safety comment
-  --> $DIR/undocumented_unsafe_blocks.rs:316:5
+  --> $DIR/undocumented_unsafe_blocks.rs:324:5
    |
 LL |     unsafe {};
    |     ^^^^^^^^^
    |
    = help: consider adding a safety comment on the preceding line
 
 error: unsafe block missing a safety comment
-  --> $DIR/undocumented_unsafe_blocks.rs:320:20
+  --> $DIR/undocumented_unsafe_blocks.rs:328:20
    |
 LL |     println!("{}", unsafe { String::from_utf8_unchecked(vec![]) });
    |                    ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^