Unrolled build for #149344

Rollup merge of #149344 - lapla-cogito:const_unwrap_sugg, r=Kivooeo

Don't suggest unwrap for Result in const

close #149316

Regarding `const fn` that returns `Result`, we should avoid suggesting unwrapping. The original issue reported cases where types didn't match, but in practice, such suggestions may also appear when methods are not found, so this PR includes a fix for that case as well.

Author: rust-timer

compiler/rustc_hir_typeck/src/fn_ctxt/suggestions.rs

@@ -2106,14 +2106,16 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
             )),
         );
 
-        let (article, kind, variant, sugg_operator) =
-            if self.tcx.is_diagnostic_item(sym::Result, adt.did()) {
-                ("a", "Result", "Err", ret_ty_matches(sym::Result))
-            } else if self.tcx.is_diagnostic_item(sym::Option, adt.did()) {
-                ("an", "Option", "None", ret_ty_matches(sym::Option))
-            } else {
-                return false;
-            };
+        let (article, kind, variant, sugg_operator) = if self.tcx.is_diagnostic_item(sym::Result, adt.did())
+            // Do not suggest `.expect()` in const context where it's not available. rust-lang/rust#149316
+            && !self.tcx.hir_is_inside_const_context(expr.hir_id)
+        {
+            ("a", "Result", "Err", ret_ty_matches(sym::Result))
+        } else if self.tcx.is_diagnostic_item(sym::Option, adt.did()) {
+            ("an", "Option", "None", ret_ty_matches(sym::Option))
+        } else {
+            return false;
+        };
         if is_ctor || !self.may_coerce(args.type_at(0), expected) {
             return false;
         }

compiler/rustc_hir_typeck/src/method/suggest.rs

@@ -3041,14 +3041,16 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                             tcx.def_span(pick.item.def_id),
                             format!("the method `{item_name}` exists on the type `{self_ty}`"),
                         );
-                        let (article, kind, variant, question) =
-                            if tcx.is_diagnostic_item(sym::Result, kind.did()) {
-                                ("a", "Result", "Err", ret_ty_matches(sym::Result))
-                            } else if tcx.is_diagnostic_item(sym::Option, kind.did()) {
-                                ("an", "Option", "None", ret_ty_matches(sym::Option))
-                            } else {
-                                return;
-                            };
+                        let (article, kind, variant, question) = if tcx.is_diagnostic_item(sym::Result, kind.did())
+                            // Do not suggest `.expect()` in const context where it's not available. rust-lang/rust#149316
+                            && !tcx.hir_is_inside_const_context(expr.hir_id)
+                        {
+                            ("a", "Result", "Err", ret_ty_matches(sym::Result))
+                        } else if tcx.is_diagnostic_item(sym::Option, kind.did()) {
+                            ("an", "Option", "None", ret_ty_matches(sym::Option))
+                        } else {
+                            return;
+                        };
                         if question {
                             err.span_suggestion_verbose(
                                 expr.span.shrink_to_hi(),

tests/ui/consts/const-result-no-expect-suggestion.rs

@@ -0,0 +1,15 @@
+const fn f(value: u32) -> Result<u32, ()> {
+    Ok(value)
+}
+
+const TEST: u32 = f(2);
+//~^ ERROR: mismatched types
+
+const fn g() -> Result<String, ()> {
+    Ok(String::new())
+}
+
+const TEST2: usize = g().len();
+//~^ ERROR: no method named `len` found for enum `Result<T, E>`
+
+fn main() {}

tests/ui/consts/const-result-no-expect-suggestion.stderr

@@ -0,0 +1,24 @@
+error[E0308]: mismatched types
+  --> $DIR/const-result-no-expect-suggestion.rs:5:19
+   |
+LL | const TEST: u32 = f(2);
+   |                   ^^^^ expected `u32`, found `Result<u32, ()>`
+   |
+   = note: expected type `u32`
+              found enum `Result<u32, ()>`
+
+error[E0599]: no method named `len` found for enum `Result<T, E>` in the current scope
+  --> $DIR/const-result-no-expect-suggestion.rs:12:26
+   |
+LL | const TEST2: usize = g().len();
+   |                          ^^^
+   |
+note: the method `len` exists on the type `String`
+  --> $SRC_DIR/alloc/src/string.rs:LL:COL
+help: there is a method `le` with a similar name, but with different arguments
+  --> $SRC_DIR/core/src/cmp.rs:LL:COL
+
+error: aborting due to 2 previous errors
+
+Some errors have detailed explanations: E0308, E0599.
+For more information about an error, try `rustc --explain E0308`.