Move unnecessary_filter_map to a submodule

2 files changed, 148 insertions, 140 deletions

diff --git a/clippy_lints/src/methods.rs b/clippy_lints/src/methods/mod.rs
index a0c9e34b861..828ef5b12bd 100644
--- a/clippy_lints/src/methods.rs
+++ b/clippy_lints/src/methods/mod.rs
@@ -1,6 +1,5 @@
 use crate::rustc::hir;
 use crate::rustc::hir::def::Def;
-use crate::rustc::hir::intravisit::{walk_expr, NestedVisitorMap, Visitor};
 use crate::rustc::lint::{in_external_macro, LateContext, LateLintPass, Lint, LintArray, LintContext, LintPass};
 use crate::rustc::ty::{self, Ty};
 use crate::rustc::{declare_tool_lint, lint_array};
@@ -9,7 +8,6 @@ use crate::syntax::ast;
 use crate::syntax::source_map::{BytePos, Span};
 use crate::utils::paths;
 use crate::utils::sugg;
-use crate::utils::usage::mutated_variables;
 use crate::utils::{
     get_arg_name, get_trait_def_id, implements_trait, in_macro, is_copy, is_expn_of, is_self, is_self_ty,
     iter_input_pats, last_path_segment, match_def_path, match_path, match_qpath, match_trait_method, match_type,
@@ -22,6 +20,8 @@ use std::borrow::Cow;
 use std::fmt;
 use std::iter;
 
+mod unnecessary_filter_map;
+
 #[derive(Clone)]
 pub struct Pass;
 
@@ -1424,144 +1424,6 @@ fn lint_unnecessary_fold(cx: &LateContext<'_, '_>, expr: &hir::Expr, fold_args:
     };
 }
 
-mod unnecessary_filter_map {
-    use super::*;
-
-    pub(super) fn lint(cx: &LateContext<'_, '_>, expr: &hir::Expr, args: &[hir::Expr]) {
-
-        if !match_trait_method(cx, expr, &paths::ITERATOR) {
-            return;
-        }
-
-        if let hir::ExprKind::Closure(_, _, body_id, ..) = args[1].node {
-
-            let body = cx.tcx.hir.body(body_id);
-            let arg_id = body.arguments[0].pat.id;
-            let mutates_arg = match mutated_variables(&body.value, cx) {
-                    Some(used_mutably) => used_mutably.contains(&arg_id),
-                    None => true,
-            };
-
-            let (mut found_mapping, mut found_filtering) = check_expression(&cx, arg_id, &body.value);
-
-            let mut return_visitor = ReturnVisitor::new(&cx, arg_id);
-            return_visitor.visit_expr(&body.value);
-            found_mapping |= return_visitor.found_mapping;
-            found_filtering |= return_visitor.found_filtering;
-
-            if !found_filtering {
-                span_lint(
-                    cx,
-                    UNNECESSARY_FILTER_MAP,
-                    expr.span,
-                    "this `.filter_map` can be written more simply using `.map`",
-                );
-                return;
-            }
-
-            if !found_mapping && !mutates_arg {
-                span_lint(
-                    cx,
-                    UNNECESSARY_FILTER_MAP,
-                    expr.span,
-                    "this `.filter_map` can be written more simply using `.filter`",
-                );
-                return;
-            }
-        }
-    }
-
-    // returns (found_mapping, found_filtering)
-    fn check_expression<'a, 'tcx: 'a>(cx: &'a LateContext<'a, 'tcx>, arg_id: ast::NodeId, expr: &'tcx hir::Expr) -> (bool, bool) {
-        match &expr.node {
-            hir::ExprKind::Call(ref func, ref args) => {
-                if_chain! {
-                    if let hir::ExprKind::Path(ref path) = func.node;
-                    then {
-                        if match_qpath(path, &paths::OPTION_SOME) {
-                            if_chain! {
-                                if let hir::ExprKind::Path(path) = &args[0].node;
-                                if let Def::Local(ref local) = cx.tables.qpath_def(path, args[0].hir_id);
-                                then {
-                                    if arg_id == *local {
-                                        return (false, false)
-                                    }
-                                }
-                            }
-                            return (true, false);
-                        } else {
-                            // We don't know. It might do anything.
-                            return (true, true);
-                        }
-                    }
-                }
-                (true, true)
-            },
-            hir::ExprKind::Block(ref block, _) => {
-                if let Some(expr) = &block.expr {
-                    check_expression(cx, arg_id, &expr)
-                } else {
-                    (false, false)
-                }
-            },
-            // There must be an else_arm or there will be a type error
-            hir::ExprKind::If(_, ref if_arm, Some(ref else_arm)) => {
-                let if_check = check_expression(cx, arg_id, if_arm);
-                let else_check = check_expression(cx, arg_id, else_arm);
-                (if_check.0 | else_check.0, if_check.1 | else_check.1)
-            },
-            hir::ExprKind::Match(_, ref arms, _) => {
-                let mut found_mapping = false;
-                let mut found_filtering = false;
-                for arm in arms {
-                    let (m, f) = check_expression(cx, arg_id, &arm.body);
-                    found_mapping |= m;
-                    found_filtering |= f;
-                }
-                (found_mapping, found_filtering)
-            },
-            hir::ExprKind::Path(path) if match_qpath(path, &paths::OPTION_NONE) => (false, true),
-            _ => (true, true)
-        }
-    }
-
-    struct ReturnVisitor<'a, 'tcx: 'a> {
-        cx: &'a LateContext<'a, 'tcx>,
-        arg_id: ast::NodeId,
-        // Found a non-None return that isn't Some(input)
-        found_mapping: bool,
-        // Found a return that isn't Some
-        found_filtering: bool,
-    }
-
-    impl<'a, 'tcx: 'a> ReturnVisitor<'a, 'tcx> {
-        fn new(cx: &'a LateContext<'a, 'tcx>, arg_id: ast::NodeId) -> ReturnVisitor<'a, 'tcx> {
-            ReturnVisitor {
-                cx,
-                arg_id,
-                found_mapping: false,
-                found_filtering: false,
-            }
-        }
-    }
-
-    impl<'a, 'tcx> Visitor<'tcx> for ReturnVisitor<'a, 'tcx> {
-        fn visit_expr(&mut self, expr: &'tcx hir::Expr) {
-            if let hir::ExprKind::Ret(Some(expr)) = &expr.node {
-                let (found_mapping, found_filtering) = check_expression(self.cx, self.arg_id, expr);
-                self.found_mapping |= found_mapping;
-                self.found_filtering |= found_filtering;
-            } else {
-                walk_expr(self, expr);
-            }
-        }
-
-        fn nested_visit_map<'this>(&'this mut self) -> NestedVisitorMap<'this, 'tcx> {
-            NestedVisitorMap::None
-        }
-    }
-}
-
 fn lint_iter_nth(cx: &LateContext<'_, '_>, expr: &hir::Expr, iter_args: &[hir::Expr], is_mut: bool) {
     let mut_str = if is_mut { "_mut" } else { "" };
     let caller_type = if derefs_to_slice(cx, &iter_args[0], cx.tables.expr_ty(&iter_args[0])).is_some() {
diff --git a/clippy_lints/src/methods/unnecessary_filter_map.rs b/clippy_lints/src/methods/unnecessary_filter_map.rs
new file mode 100644
index 00000000000..691c08ef0cc
--- /dev/null
+++ b/clippy_lints/src/methods/unnecessary_filter_map.rs
@@ -0,0 +1,146 @@
+use crate::rustc::hir::intravisit::{walk_expr, NestedVisitorMap, Visitor};
+use crate::rustc::lint::LateContext;
+use crate::rustc::hir;
+use crate::rustc::hir::def::Def;
+use crate::syntax::ast;
+use crate::utils::{match_qpath, match_trait_method, span_lint};
+use crate::utils::paths;
+use crate::utils::usage::mutated_variables;
+
+use if_chain::if_chain;
+
+use super::UNNECESSARY_FILTER_MAP;
+
+pub(super) fn lint(cx: &LateContext<'_, '_>, expr: &hir::Expr, args: &[hir::Expr]) {
+
+    if !match_trait_method(cx, expr, &paths::ITERATOR) {
+        return;
+    }
+
+    if let hir::ExprKind::Closure(_, _, body_id, ..) = args[1].node {
+
+        let body = cx.tcx.hir.body(body_id);
+        let arg_id = body.arguments[0].pat.id;
+        let mutates_arg = match mutated_variables(&body.value, cx) {
+                Some(used_mutably) => used_mutably.contains(&arg_id),
+                None => true,
+        };
+
+        let (mut found_mapping, mut found_filtering) = check_expression(&cx, arg_id, &body.value);
+
+        let mut return_visitor = ReturnVisitor::new(&cx, arg_id);
+        return_visitor.visit_expr(&body.value);
+        found_mapping |= return_visitor.found_mapping;
+        found_filtering |= return_visitor.found_filtering;
+
+        if !found_filtering {
+            span_lint(
+                cx,
+                UNNECESSARY_FILTER_MAP,
+                expr.span,
+                "this `.filter_map` can be written more simply using `.map`",
+            );
+            return;
+        }
+
+        if !found_mapping && !mutates_arg {
+            span_lint(
+                cx,
+                UNNECESSARY_FILTER_MAP,
+                expr.span,
+                "this `.filter_map` can be written more simply using `.filter`",
+            );
+            return;
+        }
+    }
+}
+
+// returns (found_mapping, found_filtering)
+fn check_expression<'a, 'tcx: 'a>(cx: &'a LateContext<'a, 'tcx>, arg_id: ast::NodeId, expr: &'tcx hir::Expr) -> (bool, bool) {
+    match &expr.node {
+        hir::ExprKind::Call(ref func, ref args) => {
+            if_chain! {
+                if let hir::ExprKind::Path(ref path) = func.node;
+                then {
+                    if match_qpath(path, &paths::OPTION_SOME) {
+                        if_chain! {
+                            if let hir::ExprKind::Path(path) = &args[0].node;
+                            if let Def::Local(ref local) = cx.tables.qpath_def(path, args[0].hir_id);
+                            then {
+                                if arg_id == *local {
+                                    return (false, false)
+                                }
+                            }
+                        }
+                        return (true, false);
+                    } else {
+                        // We don't know. It might do anything.
+                        return (true, true);
+                    }
+                }
+            }
+            (true, true)
+        },
+        hir::ExprKind::Block(ref block, _) => {
+            if let Some(expr) = &block.expr {
+                check_expression(cx, arg_id, &expr)
+            } else {
+                (false, false)
+            }
+        },
+        // There must be an else_arm or there will be a type error
+        hir::ExprKind::If(_, ref if_arm, Some(ref else_arm)) => {
+            let if_check = check_expression(cx, arg_id, if_arm);
+            let else_check = check_expression(cx, arg_id, else_arm);
+            (if_check.0 | else_check.0, if_check.1 | else_check.1)
+        },
+        hir::ExprKind::Match(_, ref arms, _) => {
+            let mut found_mapping = false;
+            let mut found_filtering = false;
+            for arm in arms {
+                let (m, f) = check_expression(cx, arg_id, &arm.body);
+                found_mapping |= m;
+                found_filtering |= f;
+            }
+            (found_mapping, found_filtering)
+        },
+        hir::ExprKind::Path(path) if match_qpath(path, &paths::OPTION_NONE) => (false, true),
+        _ => (true, true)
+    }
+}
+
+struct ReturnVisitor<'a, 'tcx: 'a> {
+    cx: &'a LateContext<'a, 'tcx>,
+    arg_id: ast::NodeId,
+    // Found a non-None return that isn't Some(input)
+    found_mapping: bool,
+    // Found a return that isn't Some
+    found_filtering: bool,
+}
+
+impl<'a, 'tcx: 'a> ReturnVisitor<'a, 'tcx> {
+    fn new(cx: &'a LateContext<'a, 'tcx>, arg_id: ast::NodeId) -> ReturnVisitor<'a, 'tcx> {
+        ReturnVisitor {
+            cx,
+            arg_id,
+            found_mapping: false,
+            found_filtering: false,
+        }
+    }
+}
+
+impl<'a, 'tcx> Visitor<'tcx> for ReturnVisitor<'a, 'tcx> {
+    fn visit_expr(&mut self, expr: &'tcx hir::Expr) {
+        if let hir::ExprKind::Ret(Some(expr)) = &expr.node {
+            let (found_mapping, found_filtering) = check_expression(self.cx, self.arg_id, expr);
+            self.found_mapping |= found_mapping;
+            self.found_filtering |= found_filtering;
+        } else {
+            walk_expr(self, expr);
+        }
+    }
+
+    fn nested_visit_map<'this>(&'this mut self) -> NestedVisitorMap<'this, 'tcx> {
+        NestedVisitorMap::None
+    }
+}