style: move precondition checking to the match guard

the match arms above put the "sanity" checks in the guard, and call only
`check_pat` in the body. With this commit, the (tuple) struct cases
follow that convention as well. Well, almost -- I think the ident check
belongs to the second category of checks, so I put it in the body as
well

Author: ada4a

clippy_utils/src/lib.rs

@@ -1983,16 +1983,25 @@ pub fn is_expr_identity_of_pat(cx: &LateContext<'_>, pat: &Pat<'_>, expr: &Expr<
             zip(before.iter().chain(after), arr).all(|(pat, expr)| is_expr_identity_of_pat(cx, pat, expr, by_hir))
         },
         (PatKind::TupleStruct(pat_ident, field_pats, dotdot), ExprKind::Call(ident, fields))
-            if dotdot.as_opt_usize().is_none()
-                && let ExprKind::Path(ident) = ident.kind =>
+            if dotdot.as_opt_usize().is_none() && field_pats.len() == fields.len() =>
         {
-            field_pats.len() == fields.len()
-                && qpath_res(&pat_ident, pat.hir_id) == qpath_res(&ident, expr.hir_id)
-                && zip(field_pats, fields).all(|(pat, expr)| is_expr_identity_of_pat(cx, pat, expr, by_hir))
-        },
-        (PatKind::Struct(pat_ident, field_pats, false), ExprKind::Struct(ident, fields, hir::StructTailExpr::None)) => {
-            field_pats.len() == fields.len()
+            // check ident
+            if let ExprKind::Path(ident) = &ident.kind
                 && qpath_res(&pat_ident, pat.hir_id) == qpath_res(ident, expr.hir_id)
+                // check fields
+                && zip(field_pats, fields).all(|(pat, expr)| is_expr_identity_of_pat(cx, pat, expr,by_hir))
+            {
+                true
+            } else {
+                false
+            }
+        },
+        (PatKind::Struct(pat_ident, field_pats, false), ExprKind::Struct(ident, fields, hir::StructTailExpr::None))
+            if field_pats.len() == fields.len() =>
+        {
+            // check ident
+            qpath_res(&pat_ident, pat.hir_id) == qpath_res(ident, expr.hir_id)
+                // check fields
                 && field_pats.iter().all(|field_pat| {
                     fields.iter().any(|field| {
                         field_pat.ident == field.ident && is_expr_identity_of_pat(cx, field_pat.pat, field.expr, by_hir)