Rollup merge of #108971 - Ezrashaw:E0532-better-binding-names, r=WaffleLapkin

error-msg: impl better suggestion for `E0532`

Fixes #106862

No test as there is already a test which is nearly identical to the example in the linked issue.

compiler/rustc_resolve/src/late/diagnostics.rs

@@ -1289,25 +1289,41 @@ impl<'a: 'ast, 'ast, 'tcx> LateResolutionVisitor<'a, '_, 'ast, 'tcx> {
                 PathSource::Expr(_) | PathSource::TupleStruct(..) | PathSource::Pat => {
                     let span = find_span(&source, err);
                     err.span_label(self.r.def_span(def_id), &format!("`{path_str}` defined here"));
-                    let (tail, descr, applicability) = match source {
-                        PathSource::Pat | PathSource::TupleStruct(..) => {
-                            ("", "pattern", Applicability::MachineApplicable)
-                        }
-                        _ => (": val", "literal", Applicability::HasPlaceholders),
-                    };
 
+                    let (tail, descr, applicability, old_fields) = match source {
+                        PathSource::Pat => ("", "pattern", Applicability::MachineApplicable, None),
+                        PathSource::TupleStruct(_, args) => (
+                            "",
+                            "pattern",
+                            Applicability::MachineApplicable,
+                            Some(
+                                args.iter()
+                                    .map(|a| self.r.tcx.sess.source_map().span_to_snippet(*a).ok())
+                                    .collect::<Vec<Option<String>>>(),
+                            ),
+                        ),
+                        _ => (": val", "literal", Applicability::HasPlaceholders, None),
+                    };
                     let field_ids = self.r.field_def_ids(def_id);
                     let (fields, applicability) = match field_ids {
-                        Some(field_ids) => (
-                            field_ids
-                                .iter()
-                                .map(|&field_id| {
-                                    format!("{}{tail}", self.r.tcx.item_name(field_id))
-                                })
-                                .collect::<Vec<String>>()
-                                .join(", "),
-                            applicability,
-                        ),
+                        Some(field_ids) => {
+                            let fields = field_ids.iter().map(|&id| self.r.tcx.item_name(id));
+
+                            let fields = if let Some(old_fields) = old_fields {
+                                fields
+                                    .enumerate()
+                                    .map(|(idx, new)| (new, old_fields.get(idx)))
+                                    .map(|(new, old)| {
+                                        let new = new.to_ident_string();
+                                        if let Some(Some(old)) = old && new != *old { format!("{}: {}", new, old) } else { new }
+                                    })
+                                    .collect::<Vec<String>>()
+                            } else {
+                                fields.map(|f| format!("{f}{tail}")).collect::<Vec<String>>()
+                            };
+
+                            (fields.join(", "), applicability)
+                        }
                         None => ("/* fields */".to_string(), Applicability::HasPlaceholders),
                     };
                     let pad = match field_ids {

tests/ui/issues/issue-19086.stderr

@@ -5,7 +5,7 @@ LL |     FooB { x: i32, y: i32 }
    |     ----------------------- `FooB` defined here
 ...
 LL |         FooB(a, b) => println!("{} {}", a, b),
-   |         ^^^^^^^^^^ help: use struct pattern syntax instead: `FooB { x, y }`
+   |         ^^^^^^^^^^ help: use struct pattern syntax instead: `FooB { x: a, y: b }`
 
 error: aborting due to previous error
 

tests/ui/pattern/issue-106862.fixed

@@ -0,0 +1,44 @@
+// run-rustfix
+
+#![allow(unused)]
+
+use Foo::{FooB, FooA};
+
+enum Foo {
+    FooA { opt_x: Option<i32>, y: i32 },
+    FooB { x: i32, y: i32 }
+}
+
+fn main() {
+    let f = FooB { x: 3, y: 4 };
+
+    match f {
+        FooB { x: a, y: b } => println!("{} {}", a, b),
+        //~^ ERROR expected tuple struct or tuple variant, found variant `FooB`
+        _ => (),
+    }
+
+    match f {
+        FooB { x, y } => println!("{} {}", x, y),
+        //~^ ERROR expected tuple struct or tuple variant, found variant `FooB`
+        _ => (),
+    }
+
+    match f {
+        FooA { opt_x: Some(x), y } => println!("{} {}", x, y),
+        //~^ ERROR expected tuple struct or tuple variant, found variant `FooA`
+        _ => (),
+    }
+
+    match f {
+        FooB { x: a, y: _ } => println!("{}", a),
+        //~^ ERROR expected tuple struct or tuple variant, found variant `FooB`
+        _ => (),
+    }
+
+    match f {
+        FooB { x, y } => (),
+        //~^ ERROR expected tuple struct or tuple variant, found variant `FooB`
+        _ => (),
+    }
+}

tests/ui/pattern/issue-106862.rs

@@ -0,0 +1,44 @@
+// run-rustfix
+
+#![allow(unused)]
+
+use Foo::{FooB, FooA};
+
+enum Foo {
+    FooA { opt_x: Option<i32>, y: i32 },
+    FooB { x: i32, y: i32 }
+}
+
+fn main() {
+    let f = FooB { x: 3, y: 4 };
+
+    match f {
+        FooB(a, b) => println!("{} {}", a, b),
+        //~^ ERROR expected tuple struct or tuple variant, found variant `FooB`
+        _ => (),
+    }
+
+    match f {
+        FooB(x, y) => println!("{} {}", x, y),
+        //~^ ERROR expected tuple struct or tuple variant, found variant `FooB`
+        _ => (),
+    }
+
+    match f {
+        FooA(Some(x), y) => println!("{} {}", x, y),
+        //~^ ERROR expected tuple struct or tuple variant, found variant `FooA`
+        _ => (),
+    }
+
+    match f {
+        FooB(a, _, _) => println!("{}", a),
+        //~^ ERROR expected tuple struct or tuple variant, found variant `FooB`
+        _ => (),
+    }
+
+    match f {
+        FooB() => (),
+        //~^ ERROR expected tuple struct or tuple variant, found variant `FooB`
+        _ => (),
+    }
+}

tests/ui/pattern/issue-106862.stderr

@@ -0,0 +1,48 @@
+error[E0532]: expected tuple struct or tuple variant, found variant `FooB`
+  --> $DIR/issue-106862.rs:16:9
+   |
+LL |     FooB { x: i32, y: i32 }
+   |     ----------------------- `FooB` defined here
+...
+LL |         FooB(a, b) => println!("{} {}", a, b),
+   |         ^^^^^^^^^^ help: use struct pattern syntax instead: `FooB { x: a, y: b }`
+
+error[E0532]: expected tuple struct or tuple variant, found variant `FooB`
+  --> $DIR/issue-106862.rs:22:9
+   |
+LL |     FooB { x: i32, y: i32 }
+   |     ----------------------- `FooB` defined here
+...
+LL |         FooB(x, y) => println!("{} {}", x, y),
+   |         ^^^^^^^^^^ help: use struct pattern syntax instead: `FooB { x, y }`
+
+error[E0532]: expected tuple struct or tuple variant, found variant `FooA`
+  --> $DIR/issue-106862.rs:28:9
+   |
+LL |     FooA { opt_x: Option<i32>, y: i32 },
+   |     ----------------------------------- `FooA` defined here
+...
+LL |         FooA(Some(x), y) => println!("{} {}", x, y),
+   |         ^^^^^^^^^^^^^^^^ help: use struct pattern syntax instead: `FooA { opt_x: Some(x), y }`
+
+error[E0532]: expected tuple struct or tuple variant, found variant `FooB`
+  --> $DIR/issue-106862.rs:34:9
+   |
+LL |     FooB { x: i32, y: i32 }
+   |     ----------------------- `FooB` defined here
+...
+LL |         FooB(a, _, _) => println!("{}", a),
+   |         ^^^^^^^^^^^^^ help: use struct pattern syntax instead: `FooB { x: a, y: _ }`
+
+error[E0532]: expected tuple struct or tuple variant, found variant `FooB`
+  --> $DIR/issue-106862.rs:40:9
+   |
+LL |     FooB { x: i32, y: i32 }
+   |     ----------------------- `FooB` defined here
+...
+LL |         FooB() => (),
+   |         ^^^^^^ help: use struct pattern syntax instead: `FooB { x, y }`
+
+error: aborting due to 5 previous errors
+
+For more information about this error, try `rustc --explain E0532`.