From f85f37583d91152b967cd0d1bd7253b339a26d42 Mon Sep 17 00:00:00 2001
From: Takayuki Maeda <takoyaki0316@gmail.com>
Date: Fri, 22 Jul 2022 15:53:00 +0900
Subject: [PATCH] suggest removing the tuple struct field for the unwrapped
 value

add a test case for macro
---
 compiler/rustc_typeck/src/check/demand.rs     | 15 +++++++
 .../suggest-removing-tulpe-struct-field.fixed | 17 ++++++++
 .../suggest-removing-tulpe-struct-field.rs    | 17 ++++++++
 ...suggest-removing-tulpe-struct-field.stderr | 41 +++++++++++++++++++
 4 files changed, 90 insertions(+)
 create mode 100644 src/test/ui/mismatched_types/suggest-removing-tulpe-struct-field.fixed
 create mode 100644 src/test/ui/mismatched_types/suggest-removing-tulpe-struct-field.rs
 create mode 100644 src/test/ui/mismatched_types/suggest-removing-tulpe-struct-field.stderr

diff --git a/compiler/rustc_typeck/src/check/demand.rs b/compiler/rustc_typeck/src/check/demand.rs
index a2d8765289c55..381c3a4ea1f7e 100644
--- a/compiler/rustc_typeck/src/check/demand.rs
+++ b/compiler/rustc_typeck/src/check/demand.rs
@@ -287,6 +287,21 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
         expr_ty: Ty<'tcx>,
     ) {
         if let ty::Adt(expected_adt, substs) = expected.kind() {
+            if let hir::ExprKind::Field(base, ident) = expr.kind {
+                let base_ty = self.typeck_results.borrow().expr_ty(base);
+                if self.can_eq(self.param_env, base_ty, expected).is_ok()
+                    && let Some(base_span) = base.span.find_ancestor_inside(expr.span)
+                {
+                    err.span_suggestion_verbose(
+                        expr.span.with_lo(base_span.hi()),
+                        format!("consider removing the tuple struct field `{ident}`"),
+                        "",
+                        Applicability::MaybeIncorrect,
+                    );
+                    return
+                }
+            }
+
             // If the expression is of type () and it's the return expression of a block,
             // we suggest adding a separate return expression instead.
             // (To avoid things like suggesting `Ok(while .. { .. })`.)
diff --git a/src/test/ui/mismatched_types/suggest-removing-tulpe-struct-field.fixed b/src/test/ui/mismatched_types/suggest-removing-tulpe-struct-field.fixed
new file mode 100644
index 0000000000000..63b65ab20fea8
--- /dev/null
+++ b/src/test/ui/mismatched_types/suggest-removing-tulpe-struct-field.fixed
@@ -0,0 +1,17 @@
+// run-rustfix
+
+macro_rules! my_wrapper {
+    ($expr:expr) => { MyWrapper($expr) }
+}
+
+pub struct MyWrapper(u32);
+
+fn main() {
+    let value = MyWrapper(123);
+    some_fn(value); //~ ERROR mismatched types
+    some_fn(my_wrapper!(123)); //~ ERROR mismatched types
+}
+
+fn some_fn(wrapped: MyWrapper) {
+    drop(wrapped);
+}
diff --git a/src/test/ui/mismatched_types/suggest-removing-tulpe-struct-field.rs b/src/test/ui/mismatched_types/suggest-removing-tulpe-struct-field.rs
new file mode 100644
index 0000000000000..2ab4e3955f336
--- /dev/null
+++ b/src/test/ui/mismatched_types/suggest-removing-tulpe-struct-field.rs
@@ -0,0 +1,17 @@
+// run-rustfix
+
+macro_rules! my_wrapper {
+    ($expr:expr) => { MyWrapper($expr) }
+}
+
+pub struct MyWrapper(u32);
+
+fn main() {
+    let value = MyWrapper(123);
+    some_fn(value.0); //~ ERROR mismatched types
+    some_fn(my_wrapper!(123).0); //~ ERROR mismatched types
+}
+
+fn some_fn(wrapped: MyWrapper) {
+    drop(wrapped);
+}
diff --git a/src/test/ui/mismatched_types/suggest-removing-tulpe-struct-field.stderr b/src/test/ui/mismatched_types/suggest-removing-tulpe-struct-field.stderr
new file mode 100644
index 0000000000000..82a7f276372c9
--- /dev/null
+++ b/src/test/ui/mismatched_types/suggest-removing-tulpe-struct-field.stderr
@@ -0,0 +1,41 @@
+error[E0308]: mismatched types
+  --> $DIR/suggest-removing-tulpe-struct-field.rs:11:13
+   |
+LL |     some_fn(value.0);
+   |     ------- ^^^^^^^ expected struct `MyWrapper`, found `u32`
+   |     |
+   |     arguments to this function are incorrect
+   |
+note: function defined here
+  --> $DIR/suggest-removing-tulpe-struct-field.rs:15:4
+   |
+LL | fn some_fn(wrapped: MyWrapper) {
+   |    ^^^^^^^ ------------------
+help: consider removing the tuple struct field `0`
+   |
+LL -     some_fn(value.0);
+LL +     some_fn(value);
+   |
+
+error[E0308]: mismatched types
+  --> $DIR/suggest-removing-tulpe-struct-field.rs:12:13
+   |
+LL |     some_fn(my_wrapper!(123).0);
+   |     ------- ^^^^^^^^^^^^^^^^^^ expected struct `MyWrapper`, found `u32`
+   |     |
+   |     arguments to this function are incorrect
+   |
+note: function defined here
+  --> $DIR/suggest-removing-tulpe-struct-field.rs:15:4
+   |
+LL | fn some_fn(wrapped: MyWrapper) {
+   |    ^^^^^^^ ------------------
+help: consider removing the tuple struct field `0`
+   |
+LL -     some_fn(my_wrapper!(123).0);
+LL +     some_fn(my_wrapper!(123));
+   |
+
+error: aborting due to 2 previous errors
+
+For more information about this error, try `rustc --explain E0308`.