Merge commit '6ed6f1e6a1a8f414ba7e6d9b8222e7e5a1686e42' into clippyup

1 files changed, 76 insertions, 0 deletions

diff --git a/clippy_lints/src/methods/map_unwrap_or.rs b/clippy_lints/src/methods/map_unwrap_or.rs
new file mode 100644
index 00000000000..63b2cf87f32
--- /dev/null
+++ b/clippy_lints/src/methods/map_unwrap_or.rs
@@ -0,0 +1,76 @@
+use crate::utils::usage::mutated_variables;
+use crate::utils::{is_type_diagnostic_item, meets_msrv, snippet, span_lint, span_lint_and_sugg};
+use rustc_errors::Applicability;
+use rustc_hir as hir;
+use rustc_lint::LateContext;
+use rustc_semver::RustcVersion;
+use rustc_span::symbol::sym;
+
+use super::MAP_UNWRAP_OR;
+
+const MAP_UNWRAP_OR_MSRV: RustcVersion = RustcVersion::new(1, 41, 0);
+
+/// lint use of `map().unwrap_or_else()` for `Option`s and `Result`s
+/// Return true if lint triggered
+pub(super) fn check<'tcx>(
+    cx: &LateContext<'tcx>,
+    expr: &'tcx hir::Expr<'_>,
+    map_args: &'tcx [hir::Expr<'_>],
+    unwrap_args: &'tcx [hir::Expr<'_>],
+    msrv: Option<&RustcVersion>,
+) -> bool {
+    if !meets_msrv(msrv, &MAP_UNWRAP_OR_MSRV) {
+        return false;
+    }
+    // lint if the caller of `map()` is an `Option`
+    let is_option = is_type_diagnostic_item(cx, cx.typeck_results().expr_ty(&map_args[0]), sym::option_type);
+    let is_result = is_type_diagnostic_item(cx, cx.typeck_results().expr_ty(&map_args[0]), sym::result_type);
+
+    if is_option || is_result {
+        // Don't make a suggestion that may fail to compile due to mutably borrowing
+        // the same variable twice.
+        let map_mutated_vars = mutated_variables(&map_args[0], cx);
+        let unwrap_mutated_vars = mutated_variables(&unwrap_args[1], cx);
+        if let (Some(map_mutated_vars), Some(unwrap_mutated_vars)) = (map_mutated_vars, unwrap_mutated_vars) {
+            if map_mutated_vars.intersection(&unwrap_mutated_vars).next().is_some() {
+                return false;
+            }
+        } else {
+            return false;
+        }
+
+        // lint message
+        let msg = if is_option {
+            "called `map(<f>).unwrap_or_else(<g>)` on an `Option` value. This can be done more directly by calling \
+            `map_or_else(<g>, <f>)` instead"
+        } else {
+            "called `map(<f>).unwrap_or_else(<g>)` on a `Result` value. This can be done more directly by calling \
+            `.map_or_else(<g>, <f>)` instead"
+        };
+        // get snippets for args to map() and unwrap_or_else()
+        let map_snippet = snippet(cx, map_args[1].span, "..");
+        let unwrap_snippet = snippet(cx, unwrap_args[1].span, "..");
+        // lint, with note if neither arg is > 1 line and both map() and
+        // unwrap_or_else() have the same span
+        let multiline = map_snippet.lines().count() > 1 || unwrap_snippet.lines().count() > 1;
+        let same_span = map_args[1].span.ctxt() == unwrap_args[1].span.ctxt();
+        if same_span && !multiline {
+            let var_snippet = snippet(cx, map_args[0].span, "..");
+            span_lint_and_sugg(
+                cx,
+                MAP_UNWRAP_OR,
+                expr.span,
+                msg,
+                "try this",
+                format!("{}.map_or_else({}, {})", var_snippet, unwrap_snippet, map_snippet),
+                Applicability::MachineApplicable,
+            );
+            return true;
+        } else if same_span && multiline {
+            span_lint(cx, MAP_UNWRAP_OR, expr.span, msg);
+            return true;
+        }
+    }
+
+    false
+}