Rollup merge of #143177 - xizheyin:143134, r=lcnr

Remove false label when `self` resolve failure does not relate to macro

Fixes rust-lang/rust#143134

In the first commit, I did some code-clean, moving `suggest*` to `suggestions/` dir.
In the second, commit, I added ui test.
In the third, I change the code, and present the test result.

r? compiler

compiler/rustc_resolve/src/late/diagnostics.rs

@@ -1183,15 +1183,23 @@ impl<'ast, 'ra, 'tcx> LateResolutionVisitor<'_, 'ast, 'ra, 'tcx> {
                 _ => "`self` value is a keyword only available in methods with a `self` parameter",
             },
         );
+
+        // using `let self` is wrong even if we're not in an associated method or if we're in a macro expansion.
+        // So, we should return early if we're in a pattern, see issue #143134.
+        if matches!(source, PathSource::Pat) {
+            return true;
+        }
+
         let is_assoc_fn = self.self_type_is_available();
         let self_from_macro = "a `self` parameter, but a macro invocation can only \
                                access identifiers it receives from parameters";
-        if let Some((fn_kind, span)) = &self.diag_metadata.current_function {
+        if let Some((fn_kind, fn_span)) = &self.diag_metadata.current_function {
             // The current function has a `self` parameter, but we were unable to resolve
             // a reference to `self`. This can only happen if the `self` identifier we
-            // are resolving came from a different hygiene context.
+            // are resolving came from a different hygiene context or a variable binding.
+            // But variable binding error is returned early above.
             if fn_kind.decl().inputs.get(0).is_some_and(|p| p.is_self()) {
-                err.span_label(*span, format!("this function has {self_from_macro}"));
+                err.span_label(*fn_span, format!("this function has {self_from_macro}"));
             } else {
                 let doesnt = if is_assoc_fn {
                     let (span, sugg) = fn_kind
@@ -1204,7 +1212,7 @@ impl<'ast, 'ra, 'tcx> LateResolutionVisitor<'_, 'ast, 'ra, 'tcx> {
                             // This avoids placing the suggestion into the visibility specifier.
                             let span = fn_kind
                                 .ident()
-                                .map_or(*span, |ident| span.with_lo(ident.span.hi()));
+                                .map_or(*fn_span, |ident| fn_span.with_lo(ident.span.hi()));
                             (
                                 self.r
                                     .tcx

tests/ui/error-codes/E0424.stderr

@@ -40,8 +40,6 @@ LL |     fn qux(&self) {
 error[E0424]: expected unit struct, unit variant or constant, found module `self`
   --> $DIR/E0424.rs:20:9
    |
-LL | fn main () {
-   |    ---- this function can't have a `self` parameter
 LL |     let self = "self";
    |         ^^^^ `self` value is a keyword and may not be bound to variables or shadowed
 

tests/ui/resolve/false-self-in-macro-issue-143134.rs

@@ -0,0 +1,10 @@
+trait T {
+    fn f(self);
+  }
+  impl T for () {
+    fn f(self) {
+        let self = (); //~ ERROR expected unit struct, unit variant or constant, found local variable `self`
+    }
+}
+
+fn main() {}

tests/ui/resolve/false-self-in-macro-issue-143134.stderr

@@ -0,0 +1,9 @@
+error[E0424]: expected unit struct, unit variant or constant, found local variable `self`
+  --> $DIR/false-self-in-macro-issue-143134.rs:6:13
+   |
+LL |         let self = ();
+   |             ^^^^ `self` value is a keyword and may not be bound to variables or shadowed
+
+error: aborting due to 1 previous error
+
+For more information about this error, try `rustc --explain E0424`.