New upstream version 1.52.1+dfsg1

[rustc.git] / src / tools / clippy / clippy_lints / src / methods / option_map_or_none.rs

diff --git a/src/tools/clippy/clippy_lints/src/methods/option_map_or_none.rs b/src/tools/clippy/clippy_lints/src/methods/option_map_or_none.rs
new file mode 100644 (file)
index 0000000..64f6ebc
--- /dev/null
+++ b/src/tools/clippy/clippy_lints/src/methods/option_map_or_none.rs
@@ -0,0 +1,78 @@
+use crate::utils::{is_type_diagnostic_item, match_qpath, paths, snippet, span_lint_and_sugg};
+use rustc_errors::Applicability;
+use rustc_hir as hir;
+use rustc_lint::LateContext;
+use rustc_span::symbol::sym;
+
+use super::OPTION_MAP_OR_NONE;
+use super::RESULT_MAP_OR_INTO_OPTION;
+
+/// lint use of `_.map_or(None, _)` for `Option`s and `Result`s
+pub(super) fn check<'tcx>(cx: &LateContext<'tcx>, expr: &'tcx hir::Expr<'_>, map_or_args: &'tcx [hir::Expr<'_>]) {
+    let is_option = is_type_diagnostic_item(cx, cx.typeck_results().expr_ty(&map_or_args[0]), sym::option_type);
+    let is_result = is_type_diagnostic_item(cx, cx.typeck_results().expr_ty(&map_or_args[0]), sym::result_type);
+
+    // There are two variants of this `map_or` lint:
+    // (1) using `map_or` as an adapter from `Result<T,E>` to `Option<T>`
+    // (2) using `map_or` as a combinator instead of `and_then`
+    //
+    // (For this lint) we don't care if any other type calls `map_or`
+    if !is_option && !is_result {
+        return;
+    }
+
+    let (lint_name, msg, instead, hint) = {
+        let default_arg_is_none = if let hir::ExprKind::Path(ref qpath) = map_or_args[1].kind {
+            match_qpath(qpath, &paths::OPTION_NONE)
+        } else {
+            return;
+        };
+
+        if !default_arg_is_none {
+            // nothing to lint!
+            return;
+        }
+
+        let f_arg_is_some = if let hir::ExprKind::Path(ref qpath) = map_or_args[2].kind {
+            match_qpath(qpath, &paths::OPTION_SOME)
+        } else {
+            false
+        };
+
+        if is_option {
+            let self_snippet = snippet(cx, map_or_args[0].span, "..");
+            let func_snippet = snippet(cx, map_or_args[2].span, "..");
+            let msg = "called `map_or(None, ..)` on an `Option` value. This can be done more directly by calling \
+                       `and_then(..)` instead";
+            (
+                OPTION_MAP_OR_NONE,
+                msg,
+                "try using `and_then` instead",
+                format!("{0}.and_then({1})", self_snippet, func_snippet),
+            )
+        } else if f_arg_is_some {
+            let msg = "called `map_or(None, Some)` on a `Result` value. This can be done more directly by calling \
+                       `ok()` instead";
+            let self_snippet = snippet(cx, map_or_args[0].span, "..");
+            (
+                RESULT_MAP_OR_INTO_OPTION,
+                msg,
+                "try using `ok` instead",
+                format!("{0}.ok()", self_snippet),
+            )
+        } else {
+            // nothing to lint!
+            return;
+        }
+    };
+
+    span_lint_and_sugg(
+        cx,
+        lint_name,
+        expr.span,
+        msg,
+        instead,
+        hint,
+        Applicability::MachineApplicable,
+    );
+}