Print the first possible panic location in the lint message

rust-lang · Jan 7, 2021 · c222abf · c222abf
1 parent 3632212
commit c222abf
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Showing 3 changed files with 45 additions and 29 deletions.
diff --git a/clippy_lints/src/doc.rs b/clippy_lints/src/doc.rs
@@ -1,6 +1,6 @@
 use crate::utils::{
     implements_trait, is_entrypoint_fn, is_type_diagnostic_item, match_panic_def_id, method_chain_args, return_ty,
-    span_lint,
+    span_lint, span_lint_and_note,
 };
 use if_chain::if_chain;
 use itertools::Itertools;
@@ -13,7 +13,7 @@ use rustc_errors::Handler;
 use rustc_hir as hir;
 use rustc_hir::intravisit::{self, NestedVisitorMap, Visitor};
 use rustc_hir::{Expr, ExprKind, QPath};
-use rustc_lint::{LateContext, LateLintPass};
+use rustc_lint::{LateContext, LateLintPass, LintContext};
 use rustc_middle::hir::map::Map;
 use rustc_middle::lint::in_external_macro;
 use rustc_middle::ty;
@@ -223,18 +223,10 @@ impl<'tcx> LateLintPass<'tcx> for DocMarkdown {
                     let mut fpu = FindPanicUnwrap {
                         cx,
                         typeck_results: cx.tcx.typeck(impl_item_def_id),
-                        found_panicking: false,
+                        panic_span: None,
                     };
                     fpu.visit_expr(&body.value);
-                    lint_for_missing_headers(
-                        cx,
-                        item.hir_id,
-                        item.span,
-                        sig,
-                        headers,
-                        Some(body_id),
-                        fpu.found_panicking,
-                    );
+                    lint_for_missing_headers(cx, item.hir_id, item.span, sig, headers, Some(body_id), fpu.panic_span);
                 }
             },
             hir::ItemKind::Impl {
@@ -257,7 +249,7 @@ impl<'tcx> LateLintPass<'tcx> for DocMarkdown {
         let headers = check_attrs(cx, &self.valid_idents, &item.attrs);
         if let hir::TraitItemKind::Fn(ref sig, ..) = item.kind {
             if !in_external_macro(cx.tcx.sess, item.span) {
-                lint_for_missing_headers(cx, item.hir_id, item.span, sig, headers, None, false);
+                lint_for_missing_headers(cx, item.hir_id, item.span, sig, headers, None, None);
             }
         }
     }
@@ -272,19 +264,11 @@ impl<'tcx> LateLintPass<'tcx> for DocMarkdown {
             let impl_item_def_id = cx.tcx.hir().local_def_id(item.hir_id);
             let mut fpu = FindPanicUnwrap {
                 cx,
-                found_panicking: false,
                 typeck_results: cx.tcx.typeck(impl_item_def_id),
+                panic_span: None,
             };
             fpu.visit_expr(&body.value);
-            lint_for_missing_headers(
-                cx,
-                item.hir_id,
-                item.span,
-                sig,
-                headers,
-                Some(body_id),
-                fpu.found_panicking,
-            );
+            lint_for_missing_headers(cx, item.hir_id, item.span, sig, headers, Some(body_id), fpu.panic_span);
         }
     }
 }
@@ -296,7 +280,7 @@ fn lint_for_missing_headers<'tcx>(
     sig: &hir::FnSig<'_>,
     headers: DocHeaders,
     body_id: Option<hir::BodyId>,
-    found_panicking: bool,
+    panic_span: Option<Span>,
 ) {
     if !cx.access_levels.is_exported(hir_id) {
         return; // Private functions do not require doc comments
@@ -309,12 +293,14 @@ fn lint_for_missing_headers<'tcx>(
             "unsafe function's docs miss `# Safety` section",
         );
     }
-    if !headers.panics && found_panicking {
-        span_lint(
+    if !headers.panics && panic_span.is_some() {
+        span_lint_and_note(
             cx,
             MISSING_PANICS_DOC,
             span,
             "docs for function which may panic missing `# Panics` section",
+            panic_span,
+            "first possible panic found here",
         );
     }
     if !headers.errors {
@@ -697,22 +683,26 @@ fn check_word(cx: &LateContext<'_>, word: &str, span: Span) {
 
 struct FindPanicUnwrap<'a, 'tcx> {
     cx: &'a LateContext<'tcx>,
-    found_panicking: bool,
+    panic_span: Option<Span>,
     typeck_results: &'tcx ty::TypeckResults<'tcx>,
 }
 
 impl<'a, 'tcx> Visitor<'tcx> for FindPanicUnwrap<'a, 'tcx> {
     type Map = Map<'tcx>;
 
     fn visit_expr(&mut self, expr: &'tcx Expr<'_>) {
+        if self.panic_span.is_some() {
+            return;
+        }
+
         // check for `begin_panic`
         if_chain! {
             if let ExprKind::Call(ref func_expr, _) = expr.kind;
             if let ExprKind::Path(QPath::Resolved(_, ref path)) = func_expr.kind;
             if let Some(path_def_id) = path.res.opt_def_id();
             if match_panic_def_id(self.cx, path_def_id);
             then {
-                self.found_panicking = true;
+                self.panic_span = Some(expr.span);
             }
         }
 

diff --git a/clippy_lints/src/utils/diagnostics.rs b/clippy_lints/src/utils/diagnostics.rs
@@ -110,7 +110,7 @@ pub fn span_lint_and_help<'a, T: LintContext>(
 pub fn span_lint_and_note<'a, T: LintContext>(
     cx: &'a T,
     lint: &'static Lint,
-    span: Span,
+    span: impl Into<MultiSpan>,
     msg: &str,
     note_span: Option<Span>,
     note: &str,

diff --git a/tests/ui/doc_panics.stderr b/tests/ui/doc_panics.stderr
@@ -8,6 +8,11 @@ LL | | }
    | |_^
    |
    = note: `-D clippy::missing-panics-doc` implied by `-D warnings`
+note: first possible panic found here
+  --> $DIR/doc_panics.rs:9:5
+   |
+LL |     result.unwrap()
+   |     ^^^^^^^^^^^^^^^
 
 error: docs for function which may panic missing `# Panics` section
   --> $DIR/doc_panics.rs:13:1
@@ -16,6 +21,13 @@ LL | / pub fn panic() {
 LL | |     panic!("This function panics")
 LL | | }
    | |_^
+   |
+note: first possible panic found here
+  --> $DIR/doc_panics.rs:14:5
+   |
+LL |     panic!("This function panics")
+   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+   = note: this error originates in a macro (in Nightly builds, run with -Z macro-backtrace for more info)
 
 error: docs for function which may panic missing `# Panics` section
   --> $DIR/doc_panics.rs:18:1
@@ -24,6 +36,13 @@ LL | / pub fn todo() {
 LL | |     todo!()
 LL | | }
    | |_^
+   |
+note: first possible panic found here
+  --> $DIR/doc_panics.rs:19:5
+   |
+LL |     todo!()
+   |     ^^^^^^^
+   = note: this error originates in a macro (in Nightly builds, run with -Z macro-backtrace for more info)
 
 error: docs for function which may panic missing `# Panics` section
   --> $DIR/doc_panics.rs:23:1
@@ -36,6 +55,13 @@ LL | |         }
 LL | |     });
 LL | | }
    | |_^
+   |
+note: first possible panic found here
+  --> $DIR/doc_panics.rs:26:13
+   |
+LL |             panic!()
+   |             ^^^^^^^^
+   = note: this error originates in a macro (in Nightly builds, run with -Z macro-backtrace for more info)
 
 error: aborting due to 4 previous errors