Simplify collect expr_ty

Author: camsteffen

clippy_lints/src/loops/needless_collect.rs

@@ -7,7 +7,7 @@ use clippy_utils::{is_trait_method, path_to_local_id};
 use if_chain::if_chain;
 use rustc_errors::Applicability;
 use rustc_hir::intravisit::{walk_block, walk_expr, NestedVisitorMap, Visitor};
-use rustc_hir::{Block, Expr, ExprKind, GenericArg, GenericArgs, HirId, PatKind, StmtKind, Ty};
+use rustc_hir::{Block, Expr, ExprKind, HirId, PatKind, StmtKind};
 use rustc_lint::LateContext;
 use rustc_middle::hir::map::Map;
 use rustc_span::sym;
@@ -24,10 +24,8 @@ fn check_needless_collect_direct_usage<'tcx>(expr: &'tcx Expr<'_>, cx: &LateCont
         if let ExprKind::MethodCall(method, _, args, _) = expr.kind;
         if let ExprKind::MethodCall(chain_method, method0_span, _, _) = args[0].kind;
         if chain_method.ident.name == sym!(collect) && is_trait_method(cx, &args[0], sym::Iterator);
-        if let Some(generic_args) = chain_method.args;
-        if let Some(GenericArg::Type(ref ty)) = generic_args.args.get(0);
-        if let Some(ty) = cx.typeck_results().node_type_opt(ty.hir_id);
         then {
+            let ty = cx.typeck_results().expr_ty(&args[0]);
             let mut applicability = Applicability::MachineApplicable;
             let is_empty_sugg = "next().is_none()".to_string();
             let method_name = &*method.ident.name.as_str();
@@ -72,19 +70,6 @@ fn check_needless_collect_direct_usage<'tcx>(expr: &'tcx Expr<'_>, cx: &LateCont
 }
 
 fn check_needless_collect_indirect_usage<'tcx>(expr: &'tcx Expr<'_>, cx: &LateContext<'tcx>) {
-    fn get_hir_id<'tcx>(ty: Option<&Ty<'tcx>>, method_args: Option<&GenericArgs<'tcx>>) -> Option<HirId> {
-        if let Some(ty) = ty {
-            return Some(ty.hir_id);
-        }
-
-        if let Some(generic_args) = method_args {
-            if let Some(GenericArg::Type(ref ty)) = generic_args.args.get(0) {
-                return Some(ty.hir_id);
-            }
-        }
-
-        None
-    }
     if let ExprKind::Block(block, _) = expr.kind {
         for stmt in block.stmts {
             if_chain! {
@@ -93,8 +78,7 @@ fn check_needless_collect_indirect_usage<'tcx>(expr: &'tcx Expr<'_>, cx: &LateCo
                 if let Some(init_expr) = local.init;
                 if let ExprKind::MethodCall(method_name, collect_span, &[ref iter_source], ..) = init_expr.kind;
                 if method_name.ident.name == sym!(collect) && is_trait_method(cx, init_expr, sym::Iterator);
-                if let Some(hir_id) = get_hir_id(local.ty, method_name.args);
-                if let Some(ty) = cx.typeck_results().node_type_opt(hir_id);
+                let ty = cx.typeck_results().expr_ty(init_expr);
                 if is_type_diagnostic_item(cx, ty, sym::vec_type) ||
                     is_type_diagnostic_item(cx, ty, sym::vecdeque_type) ||
                     is_type_diagnostic_item(cx, ty, sym::BinaryHeap) ||