fix #104700, account for item-local in inner scope for E0425

Author: chenyukang

compiler/rustc_resolve/src/late.rs

@@ -566,6 +566,9 @@ struct LateResolutionVisitor<'a, 'b, 'ast> {
     /// FIXME #4948: Reuse ribs to avoid allocation.
     ribs: PerNS<Vec<Rib<'a>>>,
 
+    /// Previous poped `rib`, only used for diagnostic.
+    last_block_rib: Option<Rib<'a>>,
+
     /// The current set of local scopes, for labels.
     label_ribs: Vec<Rib<'a, NodeId>>,
 
@@ -1168,6 +1171,7 @@ impl<'a: 'ast, 'b, 'ast> LateResolutionVisitor<'a, 'b, 'ast> {
                 type_ns: vec![Rib::new(start_rib_kind)],
                 macro_ns: vec![Rib::new(start_rib_kind)],
             },
+            last_block_rib: None,
             label_ribs: Vec::new(),
             lifetime_ribs: Vec::new(),
             lifetime_elision_candidates: None,
@@ -3756,7 +3760,7 @@ impl<'a: 'ast, 'b, 'ast> LateResolutionVisitor<'a, 'b, 'ast> {
             self.ribs[ValueNS].pop();
             self.label_ribs.pop();
         }
-        self.ribs[ValueNS].pop();
+        self.last_block_rib = self.ribs[ValueNS].pop();
         if anonymous_module.is_some() {
             self.ribs[TypeNS].pop();
         }

compiler/rustc_resolve/src/late/diagnostics.rs

@@ -614,6 +614,22 @@ impl<'a: 'ast, 'ast> LateResolutionVisitor<'a, '_, 'ast> {
                 return (true, candidates);
             }
         }
+
+        // Try to find in last block rib
+        if let Some(rib) = &self.last_block_rib {
+            for (ident, &res) in &rib.bindings {
+                if let Res::Local(_) = res && path.len() == 1 &&
+                    ident.span.eq_ctxt(path[0].ident.span) &&
+                    ident.name == path[0].ident.name {
+                    err.span_help(
+                        ident.span,
+                        &format!("the binding `{}` is available in a different scope in the same function", path_str),
+                    );
+                    return (true, candidates);
+                }
+            }
+        }
+
         return (false, candidates);
     }
 

src/test/ui/resolve/issue-104700-inner_scope.rs

@@ -0,0 +1,11 @@
+fn main() {
+    let foo = 1;
+    {
+        let bar = 2;
+        let test_func = |x| x > 3;
+    }
+    if bar == 2 { //~ ERROR cannot find value
+        println!("yes");
+    }
+    test_func(1); //~ ERROR cannot find function
+}

src/test/ui/resolve/issue-104700-inner_scope.stderr

@@ -0,0 +1,21 @@
+error[E0425]: cannot find value `bar` in this scope
+  --> $DIR/issue-104700-inner_scope.rs:7:8
+   |
+LL |     if bar == 2 {
+   |        ^^^
+   |
+help: the binding `bar` is available in a different scope in the same function
+  --> $DIR/issue-104700-inner_scope.rs:4:13
+   |
+LL |         let bar = 2;
+   |             ^^^
+
+error[E0425]: cannot find function `test_func` in this scope
+  --> $DIR/issue-104700-inner_scope.rs:10:5
+   |
+LL |     test_func(1);
+   |     ^^^^^^^^^ not found in this scope
+
+error: aborting due to 2 previous errors
+
+For more information about this error, try `rustc --explain E0425`.