From 7b837e075a335d482c583b574ebaf5006738655e Mon Sep 17 00:00:00 2001
From: Kevin Reid <kpreid@switchb.org>
Date: Tue, 29 Aug 2023 13:41:33 -0700
Subject: [PATCH] Don't suggest adding parentheses to call an inaccessible
 method.

Previously, the test code would emit E0615, thus revealing the existence
of private methods that the programmer probably does not care about.
Now it ignores their existence instead, producing error E0609 (no field).

The motivating example is:

```rust
let x = std::rc::Rc::new(());
x.inner;
```

which would previously mention the private method `Rc::inner()`, even
though `Rc<T>` intentionally has no public methods so that it can be a
transparent smart pointer for any `T`.
---
 compiler/rustc_hir_typeck/src/expr.rs            |  2 +-
 tests/ui/error-codes/E0609-private-method.rs     | 16 ++++++++++++++++
 tests/ui/error-codes/E0609-private-method.stderr |  9 +++++++++
 3 files changed, 26 insertions(+), 1 deletion(-)
 create mode 100644 tests/ui/error-codes/E0609-private-method.rs
 create mode 100644 tests/ui/error-codes/E0609-private-method.stderr

diff --git a/compiler/rustc_hir_typeck/src/expr.rs b/compiler/rustc_hir_typeck/src/expr.rs
index 7cea40fdd64c..72c58bf1c2d6 100644
--- a/compiler/rustc_hir_typeck/src/expr.rs
+++ b/compiler/rustc_hir_typeck/src/expr.rs
@@ -2314,7 +2314,7 @@ fn check_field(
             field,
             base_ty,
             expr.hir_id,
-            true,
+            false, // don't mention or suggest non-accessible methods
             expected.only_has_type(self),
         ) {
             self.ban_take_value_of_method(expr, base_ty, field)
diff --git a/tests/ui/error-codes/E0609-private-method.rs b/tests/ui/error-codes/E0609-private-method.rs
new file mode 100644
index 000000000000..dfa97ad9a6f4
--- /dev/null
+++ b/tests/ui/error-codes/E0609-private-method.rs
@@ -0,0 +1,16 @@
+// This error is an E0609 and *not* an E0615 because the fact that the method exists is not
+// relevant.
+mod foo {
+    pub struct Foo {
+        x: u32,
+    }
+
+    impl Foo {
+        fn method(&self) {}
+    }
+}
+
+fn main() {
+    let f = foo::Foo { x: 0 };
+    f.method; //~ ERROR E0609
+}
diff --git a/tests/ui/error-codes/E0609-private-method.stderr b/tests/ui/error-codes/E0609-private-method.stderr
new file mode 100644
index 000000000000..d2a11e906274
--- /dev/null
+++ b/tests/ui/error-codes/E0609-private-method.stderr
@@ -0,0 +1,9 @@
+error[E0609]: no field `method` on type `Foo`
+  --> $DIR/E0609-private-method.rs:15:7
+   |
+LL |     f.method;
+   |       ^^^^^^ unknown field
+
+error: aborting due to previous error
+
+For more information about this error, try `rustc --explain E0609`.