Add visitors for PatField and ExprField.

This helps simplify the code. It also fixes it to use the correct parent
when lowering. One consequence is the `non_snake_case` lint needed
to change the way it looked for parent nodes in a struct pattern.

This also includes a small fix to use the correct `Target` for
expression field attribute validation.

6 files changed, 55 insertions, 73 deletions

diff --git a/compiler/rustc_ast_lowering/src/index.rs b/compiler/rustc_ast_lowering/src/index.rs
index ea35cf3de04..899e0dd5cc3 100644
--- a/compiler/rustc_ast_lowering/src/index.rs
+++ b/compiler/rustc_ast_lowering/src/index.rs
@@ -193,17 +193,19 @@ impl<'a, 'hir> Visitor<'hir> for NodeCollector<'a, 'hir> {
 
     fn visit_pat(&mut self, pat: &'hir Pat<'hir>) {
         self.insert(pat.span, pat.hir_id, Node::Pat(pat));
-        if let PatKind::Struct(_, fields, _) = pat.kind {
-            for field in fields {
-                self.insert(field.span, field.hir_id, Node::PatField(field));
-            }
-        }
 
         self.with_parent(pat.hir_id, |this| {
             intravisit::walk_pat(this, pat);
         });
     }
 
+    fn visit_pat_field(&mut self, field: &'hir PatField<'hir>) {
+        self.insert(field.span, field.hir_id, Node::PatField(field));
+        self.with_parent(field.hir_id, |this| {
+            intravisit::walk_pat_field(this, field);
+        });
+    }
+
     fn visit_arm(&mut self, arm: &'hir Arm<'hir>) {
         let node = Node::Arm(arm);
 
diff --git a/compiler/rustc_hir/src/intravisit.rs b/compiler/rustc_hir/src/intravisit.rs
index 51b1bfad8a0..900370937f7 100644
--- a/compiler/rustc_hir/src/intravisit.rs
+++ b/compiler/rustc_hir/src/intravisit.rs
@@ -325,6 +325,9 @@ pub trait Visitor<'v>: Sized {
     fn visit_pat(&mut self, p: &'v Pat<'v>) {
         walk_pat(self, p)
     }
+    fn visit_pat_field(&mut self, f: &'v PatField<'v>) {
+        walk_pat_field(self, f)
+    }
     fn visit_array_length(&mut self, len: &'v ArrayLen) {
         walk_array_len(self, len)
     }
@@ -337,6 +340,9 @@ pub trait Visitor<'v>: Sized {
     fn visit_let_expr(&mut self, lex: &'v Let<'v>) {
         walk_let_expr(self, lex)
     }
+    fn visit_expr_field(&mut self, field: &'v ExprField<'v>) {
+        walk_expr_field(self, field)
+    }
     fn visit_ty(&mut self, t: &'v Ty<'v>) {
         walk_ty(self, t)
     }
@@ -761,11 +767,7 @@ pub fn walk_pat<'v, V: Visitor<'v>>(visitor: &mut V, pattern: &'v Pat<'v>) {
         }
         PatKind::Struct(ref qpath, fields, _) => {
             visitor.visit_qpath(qpath, pattern.hir_id, pattern.span);
-            for field in fields {
-                visitor.visit_id(field.hir_id);
-                visitor.visit_ident(field.ident);
-                visitor.visit_pat(&field.pat)
-            }
+            walk_list!(visitor, visit_pat_field, fields);
         }
         PatKind::Or(pats) => walk_list!(visitor, visit_pat, pats),
         PatKind::Tuple(tuple_elements, _) => {
@@ -792,6 +794,12 @@ pub fn walk_pat<'v, V: Visitor<'v>>(visitor: &mut V, pattern: &'v Pat<'v>) {
     }
 }
 
+pub fn walk_pat_field<'v, V: Visitor<'v>>(visitor: &mut V, field: &'v PatField<'v>) {
+    visitor.visit_id(field.hir_id);
+    visitor.visit_ident(field.ident);
+    visitor.visit_pat(&field.pat)
+}
+
 pub fn walk_foreign_item<'v, V: Visitor<'v>>(visitor: &mut V, foreign_item: &'v ForeignItem<'v>) {
     visitor.visit_id(foreign_item.hir_id());
     visitor.visit_ident(foreign_item.ident);
@@ -1059,6 +1067,12 @@ pub fn walk_let_expr<'v, V: Visitor<'v>>(visitor: &mut V, let_expr: &'v Let<'v>)
     walk_list!(visitor, visit_ty, let_expr.ty);
 }
 
+pub fn walk_expr_field<'v, V: Visitor<'v>>(visitor: &mut V, field: &'v ExprField<'v>) {
+    visitor.visit_id(field.hir_id);
+    visitor.visit_ident(field.ident);
+    visitor.visit_expr(&field.expr)
+}
+
 pub fn walk_expr<'v, V: Visitor<'v>>(visitor: &mut V, expression: &'v Expr<'v>) {
     visitor.visit_id(expression.hir_id);
     match expression.kind {
@@ -1073,11 +1087,7 @@ pub fn walk_expr<'v, V: Visitor<'v>>(visitor: &mut V, expression: &'v Expr<'v>)
         }
         ExprKind::Struct(ref qpath, fields, ref optional_base) => {
             visitor.visit_qpath(qpath, expression.hir_id, expression.span);
-            for field in fields {
-                visitor.visit_id(field.hir_id);
-                visitor.visit_ident(field.ident);
-                visitor.visit_expr(&field.expr)
-            }
+            walk_list!(visitor, visit_expr_field, fields);
             walk_list!(visitor, visit_expr, optional_base);
         }
         ExprKind::Tup(subexpressions) => {
diff --git a/compiler/rustc_lint/src/levels.rs b/compiler/rustc_lint/src/levels.rs
index bae36647992..1cabb58bbeb 100644
--- a/compiler/rustc_lint/src/levels.rs
+++ b/compiler/rustc_lint/src/levels.rs
@@ -761,26 +761,15 @@ impl<'tcx> intravisit::Visitor<'tcx> for LintLevelMapBuilder<'tcx> {
     }
 
     fn visit_expr(&mut self, e: &'tcx hir::Expr<'tcx>) {
-        match e.kind {
-            hir::ExprKind::Struct(qpath, fields, base_expr) => {
-                self.with_lint_attrs(e.hir_id, |builder| {
-                    builder.visit_qpath(qpath, e.hir_id, e.span);
-                    for field in fields {
-                        builder.with_lint_attrs(field.hir_id, |field_builder| {
-                            field_builder.visit_id(field.hir_id);
-                            field_builder.visit_ident(field.ident);
-                            field_builder.visit_expr(field.expr);
-                        });
-                    }
-                    if let Some(base_expr) = base_expr {
-                        builder.visit_expr(base_expr);
-                    }
-                });
-            }
-            _ => self.with_lint_attrs(e.hir_id, |builder| {
-                intravisit::walk_expr(builder, e);
-            }),
-        }
+        self.with_lint_attrs(e.hir_id, |builder| {
+            intravisit::walk_expr(builder, e);
+        })
+    }
+
+    fn visit_expr_field(&mut self, field: &'tcx hir::ExprField<'tcx>) {
+        self.with_lint_attrs(field.hir_id, |builder| {
+            intravisit::walk_expr_field(builder, field);
+        })
     }
 
     fn visit_field_def(&mut self, s: &'tcx hir::FieldDef<'tcx>) {
@@ -819,20 +808,10 @@ impl<'tcx> intravisit::Visitor<'tcx> for LintLevelMapBuilder<'tcx> {
         });
     }
 
-    fn visit_pat(&mut self, p: &'tcx hir::Pat<'tcx>) {
-        match &p.kind {
-            hir::PatKind::Struct(qpath, fields, _) => {
-                self.visit_qpath(&qpath, p.hir_id, p.span);
-                for field in *fields {
-                    self.with_lint_attrs(field.hir_id, |builder| {
-                        builder.visit_id(field.hir_id);
-                        builder.visit_ident(field.ident);
-                        builder.visit_pat(field.pat);
-                    })
-                }
-            }
-            _ => intravisit::walk_pat(self, p),
-        }
+    fn visit_pat_field(&mut self, field: &'tcx hir::PatField<'tcx>) {
+        self.with_lint_attrs(field.hir_id, |builder| {
+            intravisit::walk_pat_field(builder, field);
+        })
     }
 
     fn visit_generic_param(&mut self, p: &'tcx hir::GenericParam<'tcx>) {
diff --git a/compiler/rustc_lint/src/nonstandard_style.rs b/compiler/rustc_lint/src/nonstandard_style.rs
index 8d04d68bf1c..2868aabfa07 100644
--- a/compiler/rustc_lint/src/nonstandard_style.rs
+++ b/compiler/rustc_lint/src/nonstandard_style.rs
@@ -437,19 +437,14 @@ impl<'tcx> LateLintPass<'tcx> for NonSnakeCase {
 
     fn check_pat(&mut self, cx: &LateContext<'_>, p: &hir::Pat<'_>) {
         if let PatKind::Binding(_, hid, ident, _) = p.kind {
-            if let hir::Node::Pat(parent_pat) = cx.tcx.hir().get(cx.tcx.hir().get_parent_node(hid))
+            if let hir::Node::PatField(field) = cx.tcx.hir().get(cx.tcx.hir().get_parent_node(hid))
             {
-                if let PatKind::Struct(_, field_pats, _) = &parent_pat.kind {
-                    if field_pats
-                        .iter()
-                        .any(|field| !field.is_shorthand && field.pat.hir_id == p.hir_id)
-                    {
-                        // Only check if a new name has been introduced, to avoid warning
-                        // on both the struct definition and this pattern.
-                        self.check_snake_case(cx, "variable", &ident);
-                    }
-                    return;
+                if !field.is_shorthand {
+                    // Only check if a new name has been introduced, to avoid warning
+                    // on both the struct definition and this pattern.
+                    self.check_snake_case(cx, "variable", &ident);
                 }
+                return;
             }
             self.check_snake_case(cx, "variable", &ident);
         }
diff --git a/compiler/rustc_passes/src/check_attr.rs b/compiler/rustc_passes/src/check_attr.rs
index 0eb6f401b38..5789531d2ff 100644
--- a/compiler/rustc_passes/src/check_attr.rs
+++ b/compiler/rustc_passes/src/check_attr.rs
@@ -2065,14 +2065,14 @@ impl<'tcx> Visitor<'tcx> for CheckAttrVisitor<'tcx> {
         };
 
         self.check_attributes(expr.hir_id, expr.span, target, None);
-        if let hir::ExprKind::Struct(_, fields, _) = expr.kind {
-            for field in fields {
-                self.check_attributes(field.hir_id, field.span, Target::PatField, None);
-            }
-        }
         intravisit::walk_expr(self, expr)
     }
 
+    fn visit_expr_field(&mut self, field: &'tcx hir::ExprField<'tcx>) {
+        self.check_attributes(field.hir_id, field.span, Target::ExprField, None);
+        intravisit::walk_expr_field(self, field)
+    }
+
     fn visit_variant(&mut self, variant: &'tcx hir::Variant<'tcx>) {
         self.check_attributes(variant.id, variant.span, Target::Variant, None);
         intravisit::walk_variant(self, variant)
@@ -2084,13 +2084,9 @@ impl<'tcx> Visitor<'tcx> for CheckAttrVisitor<'tcx> {
         intravisit::walk_param(self, param);
     }
 
-    fn visit_pat(&mut self, p: &'tcx hir::Pat<'tcx>) {
-        if let hir::PatKind::Struct(_, fields, _) = p.kind {
-            for field in fields {
-                self.check_attributes(field.hir_id, field.span, Target::PatField, None);
-            }
-        }
-        intravisit::walk_pat(self, p);
+    fn visit_pat_field(&mut self, field: &'tcx hir::PatField<'tcx>) {
+        self.check_attributes(field.hir_id, field.span, Target::PatField, None);
+        intravisit::walk_pat_field(self, field);
     }
 }
 
diff --git a/src/test/ui/lint/unused/unused_attributes-must_use.stderr b/src/test/ui/lint/unused/unused_attributes-must_use.stderr
index 69cd5302c5c..dd112c23e5d 100644
--- a/src/test/ui/lint/unused/unused_attributes-must_use.stderr
+++ b/src/test/ui/lint/unused/unused_attributes-must_use.stderr
@@ -105,7 +105,7 @@ error: `#[must_use]` has no effect when applied to an match arm
 LL |         #[must_use]
    |         ^^^^^^^^^^^
 
-error: `#[must_use]` has no effect when applied to a pattern field
+error: `#[must_use]` has no effect when applied to a struct field
   --> $DIR/unused_attributes-must_use.rs:129:28
    |
 LL |     let s = PatternField { #[must_use]  foo: 123 };