fix(collapsible_match): exclude binding modes from struct field pattern suggestions

Author: ada4a

clippy_lints/src/matches/collapsible_match.rs

@@ -13,6 +13,7 @@ use rustc_hir::LangItem::OptionNone;
 use rustc_hir::{Arm, Expr, ExprKind, HirId, Pat, PatExpr, PatExprKind, PatKind};
 use rustc_lint::LateContext;
 use rustc_span::Span;
+use rustc_span::symbol::Ident;
 
 use super::{COLLAPSIBLE_MATCH, pat_contains_disallowed_or};
 
@@ -70,7 +71,7 @@ fn check_arm<'tcx>(
         && !pat_contains_disallowed_or(cx, inner_then_pat, msrv)
         // the binding must come from the pattern of the containing match arm
         // ..<local>.. => match <local> { .. }
-        && let (Some(binding_span), is_innermost_parent_pat_struct) =
+        && let (Some((binding_ident, binding_span)), is_innermost_parent_pat_struct) =
             find_pat_binding_and_is_innermost_parent_pat_struct(outer_pat, binding_id)
         // the "else" branches must be equal
         && match (outer_else_body, inner_else_body) {
@@ -103,7 +104,7 @@ fn check_arm<'tcx>(
         // collapsing patterns need an explicit field name in struct pattern matching
         // ex: Struct {x: Some(1)}
         let replace_msg = if is_innermost_parent_pat_struct {
-            format!(", prefixed by `{}: `", snippet(cx, binding_span, "their field name"))
+            format!(", prefixed by `{}: `", binding_ident)
         } else {
             String::new()
         };
@@ -140,16 +141,16 @@ fn arm_is_wild_like(cx: &LateContext<'_>, arm: &Arm<'_>) -> bool {
     }
 }
 
-fn find_pat_binding_and_is_innermost_parent_pat_struct(pat: &Pat<'_>, hir_id: HirId) -> (Option<Span>, bool) {
-    let mut span = None;
+fn find_pat_binding_and_is_innermost_parent_pat_struct(pat: &Pat<'_>, hir_id: HirId) -> (Option<(Ident, Span)>, bool) {
+    let mut binding = None;
     let mut is_innermost_parent_pat_struct = false;
-    pat.walk_short(|p| match &p.kind {
+    pat.walk_short(|p| match p.kind {
         // ignore OR patterns
         PatKind::Or(_) => false,
-        PatKind::Binding(_bm, _, _ident, _) => {
+        PatKind::Binding(_bm, _, ident, _) => {
             let found = p.hir_id == hir_id;
             if found {
-                span = Some(p.span);
+                binding = Some((ident, p.span));
             }
             !found
         },
@@ -158,7 +159,7 @@ fn find_pat_binding_and_is_innermost_parent_pat_struct(pat: &Pat<'_>, hir_id: Hi
             true
         },
     });
-    (span, is_innermost_parent_pat_struct)
+    (binding, is_innermost_parent_pat_struct)
 }
 
 /// Builds a chain of reference-manipulation method calls (e.g., `.as_ref()`, `.as_mut()`,

tests/ui/collapsible_match.rs

@@ -304,6 +304,27 @@ pub fn test_2(x: Issue9647) {
     }
 }
 
+mod issue_13287 {
+    enum Token {
+        Name,
+        Other,
+    }
+
+    struct Error {
+        location: u32,
+        token: Option<Token>,
+    }
+
+    fn struct_field_pat_with_binding_mode(err: Option<Error>) {
+        if let Some(Error { ref token, .. }) = err {
+            if let Some(Token::Name) = token {
+                //~^ collapsible_match
+                println!("token used as a ref");
+            }
+        }
+    }
+}
+
 pub fn issue_14155() {
     let mut arr = ["a", "b", "c"];
     if let Some(last) = arr.last() {

tests/ui/collapsible_match.stderr

@@ -250,8 +250,25 @@ LL |     if let Issue9647::A { a: Some(a), .. } = x {
 LL |         if let Some(u) = a {
    |                ^^^^^^^ with this pattern
 
+error: this `if let` can be collapsed into the outer `if let`
+  --> tests/ui/collapsible_match.rs:320:13
+   |
+LL | /             if let Some(Token::Name) = token {
+LL | |
+LL | |                 println!("token used as a ref");
+LL | |             }
+   | |_____________^
+   |
+help: the outer pattern can be modified to include the inner pattern
+  --> tests/ui/collapsible_match.rs:319:29
+   |
+LL |         if let Some(Error { ref token, .. }) = err {
+   |                             ^^^^^^^^^ replace this binding
+LL |             if let Some(Token::Name) = token {
+   |                    ^^^^^^^^^^^^^^^^^ with this pattern, prefixed by `token: `
+
 error: this `match` can be collapsed into the outer `if let`
-  --> tests/ui/collapsible_match.rs:310:9
+  --> tests/ui/collapsible_match.rs:331:9
    |
 LL | /         match *last {
 LL | |
@@ -263,7 +280,7 @@ LL | |         }
    | |_________^
    |
 help: the outer pattern can be modified to include the inner pattern
-  --> tests/ui/collapsible_match.rs:309:17
+  --> tests/ui/collapsible_match.rs:330:17
    |
 LL |     if let Some(last) = arr.last() {
    |                 ^^^^    ---------- use: `arr.last().copied()`
@@ -274,7 +291,7 @@ LL |             "a" | "b" => {
    |             ^^^^^^^^^ with this pattern
 
 error: this `match` can be collapsed into the outer `if let`
-  --> tests/ui/collapsible_match.rs:320:9
+  --> tests/ui/collapsible_match.rs:341:9
    |
 LL | /         match &last {
 LL | |
@@ -286,7 +303,7 @@ LL | |         }
    | |_________^
    |
 help: the outer pattern can be modified to include the inner pattern
-  --> tests/ui/collapsible_match.rs:319:17
+  --> tests/ui/collapsible_match.rs:340:17
    |
 LL |     if let Some(last) = arr.last() {
    |                 ^^^^    ---------- use: `arr.last().as_ref()`
@@ -297,7 +314,7 @@ LL |             &&"a" | &&"b" => {
    |             ^^^^^^^^^^^^^ with this pattern
 
 error: this `match` can be collapsed into the outer `if let`
-  --> tests/ui/collapsible_match.rs:330:9
+  --> tests/ui/collapsible_match.rs:351:9
    |
 LL | /         match &mut last {
 LL | |
@@ -309,7 +326,7 @@ LL | |         }
    | |_________^
    |
 help: the outer pattern can be modified to include the inner pattern
-  --> tests/ui/collapsible_match.rs:329:17
+  --> tests/ui/collapsible_match.rs:350:17
    |
 LL |     if let Some(mut last) = arr.last_mut() {
    |                 ^^^^^^^^    -------------- use: `arr.last_mut().as_mut()`
@@ -319,5 +336,5 @@ LL |     if let Some(mut last) = arr.last_mut() {
 LL |             &mut &mut "a" | &mut &mut "b" => {
    |             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ with this pattern
 
-error: aborting due to 16 previous errors
+error: aborting due to 17 previous errors