Don't lint various match lints when expanded by a proc-macro

1 files changed, 19 insertions, 0 deletions

diff --git a/clippy_utils/src/source.rs b/clippy_utils/src/source.rs
index dbad607c58e..beed7326803 100644
--- a/clippy_utils/src/source.rs
+++ b/clippy_utils/src/source.rs
@@ -7,9 +7,28 @@ use rustc_errors::Applicability;
 use rustc_hir::{Expr, ExprKind};
 use rustc_lint::{LateContext, LintContext};
 use rustc_span::hygiene;
+use rustc_span::source_map::SourceMap;
 use rustc_span::{BytePos, Pos, Span, SyntaxContext};
 use std::borrow::Cow;
 
+/// Checks if the span starts with the given text. This will return false if the span crosses
+/// multiple files or if source is not available.
+///
+/// This is used to check for proc macros giving unhelpful spans to things.
+pub fn span_starts_with<T: LintContext>(cx: &T, span: Span, text: &str) -> bool {
+    fn helper(sm: &SourceMap, span: Span, text: &str) -> bool {
+        let pos = sm.lookup_byte_offset(span.lo());
+        let Some(ref src) = pos.sf.src else {
+            return false;
+        };
+        let end = span.hi() - pos.sf.start_pos;
+        src.get(pos.pos.0 as usize..end.0 as usize)
+            // Expression spans can include wrapping parenthesis. Remove them first.
+            .map_or(false, |s| s.trim_start_matches('(').starts_with(text))
+    }
+    helper(cx.sess().source_map(), span, text)
+}
+
 /// Like `snippet_block`, but add braces if the expr is not an `ExprKind::Block`.
 /// Also takes an `Option<String>` which can be put inside the braces.
 pub fn expr_block<'a, T: LintContext>(