Auto merge of rust-lang#6917 - MysteryJump:fix-manual-unwrap-or-const-fn, r=giraffate

Fix false-positive `manual_unwrap_or` inside const fn

Fixes rust-lang#6898

changelog:  Fix false-positive for manual_unwrap_or in const fn.

Author: bors

clippy_lints/src/manual_unwrap_or.rs

@@ -1,6 +1,6 @@
 use crate::consts::constant_simple;
 use crate::utils;
-use crate::utils::{path_to_local_id, sugg};
+use crate::utils::{in_constant, path_to_local_id, sugg};
 use clippy_utils::diagnostics::span_lint_and_sugg;
 use clippy_utils::source::{indent_of, reindent_multiline, snippet_opt};
 use clippy_utils::ty::is_type_diagnostic_item;
@@ -45,7 +45,7 @@ declare_lint_pass!(ManualUnwrapOr => [MANUAL_UNWRAP_OR]);
 
 impl LateLintPass<'_> for ManualUnwrapOr {
     fn check_expr(&mut self, cx: &LateContext<'tcx>, expr: &'tcx Expr<'tcx>) {
-        if in_external_macro(cx.sess(), expr.span) {
+        if in_external_macro(cx.sess(), expr.span) || in_constant(cx, expr.hir_id) {
             return;
         }
         lint_manual_unwrap_or(cx, expr);

tests/ui/manual_unwrap_or.fixed

@@ -136,4 +136,19 @@ fn result_unwrap_or() {
     };
 }
 
+// don't lint in const fn
+const fn const_fn_option_unwrap_or() {
+    match Some(1) {
+        Some(s) => s,
+        None => 0,
+    };
+}
+
+const fn const_fn_result_unwrap_or() {
+    match Ok::<&str, &str>("Alice") {
+        Ok(s) => s,
+        Err(_) => "Bob",
+    };
+}
+
 fn main() {}

tests/ui/manual_unwrap_or.rs

@@ -175,4 +175,19 @@ fn result_unwrap_or() {
     };
 }
 
+// don't lint in const fn
+const fn const_fn_option_unwrap_or() {
+    match Some(1) {
+        Some(s) => s,
+        None => 0,
+    };
+}
+
+const fn const_fn_result_unwrap_or() {
+    match Ok::<&str, &str>("Alice") {
+        Ok(s) => s,
+        Err(_) => "Bob",
+    };
+}
+
 fn main() {}