Support struct patterns

Author: est31

clippy_lints/src/manual_let_else.rs

@@ -147,8 +147,8 @@ fn emit_manual_let_else(
         "this could be rewritten as `let...else`",
         |diag| {
             // This is far from perfect, for example there needs to be:
-            // * tracking for multi-binding cases: let (foo, bar) = if let (Some(foo), Ok(bar)) = ...
-            // * renamings of the bindings for many `PatKind`s like structs, slices, etc.
+            // * renamings of the bindings for many `PatKind`s like slices, etc.
+            // * limitations in the existing replacement algorithms
             // * unused binding collision detection with existing ones
             // for this to be machine applicable.
             let mut app = Applicability::HasPlaceholders;
@@ -227,6 +227,33 @@ fn replace_in_pattern(
                 }
                 return or_pat;
             },
+            PatKind::Struct(path, fields, has_dot_dot) => {
+                let fields = fields
+                    .iter()
+                    .map(|fld| {
+                        if let PatKind::Binding(_, _, name, None) = fld.pat.kind &&
+                            let Some(pat_to_put) = ident_map.get(&name.name)
+                        {
+                            let (sn_fld_name, _) = snippet_with_context(cx, fld.ident.span, span.ctxt(), "", app);
+                            let (sn_ptp, _) = snippet_with_context(cx, pat_to_put.span, span.ctxt(), "", app);
+                            // TODO: this is a bit of a hack, but it does its job. Ideally, we'd check if pat_to_put is
+                            // a PatKind::Binding but that is also hard to get right.
+                            if sn_fld_name == sn_ptp {
+                                // Field init shorthand
+                                return format!("{sn_fld_name}");
+                            }
+                            return format!("{sn_fld_name}: {sn_ptp}");
+                        }
+                        let (sn_fld, _) = snippet_with_context(cx, fld.span, span.ctxt(), "", app);
+                        sn_fld.into_owned()
+                    })
+                    .collect::<Vec<_>>();
+                let fields_string = fields.join(", ");
+
+                let dot_dot_str = if has_dot_dot { " .." } else { "" };
+                let (sn_pth, _) = snippet_with_context(cx, path.span(), span.ctxt(), "", app);
+                return format!("{sn_pth} {{ {fields_string}{dot_dot_str} }}");
+            },
             // Replace the variable name iff `TupleStruct` has one argument like `Variant(v)`.
             PatKind::TupleStruct(ref w, args, dot_dot_pos) => {
                 let mut args = args

tests/ui/manual_let_else.rs

@@ -163,6 +163,27 @@ fn fire() {
 
     // () is preserved: a bit of an edge case but make sure it stays around
     let w = if let (Some(v), ()) = (g(), ()) { v } else { return };
+
+    // Tuple structs work
+    let w = if let Some(S { v: x }) = Some(S { v: 0 }) {
+        x
+    } else {
+        return;
+    };
+
+    // Field init shorthand is suggested
+    let v = if let Some(S { v: x }) = Some(S { v: 0 }) {
+        x
+    } else {
+        return;
+    };
+
+    // Multi-field structs also work
+    let (x, S { v }, w) = if let Some(U { v, w, x }) = None::<U<S<()>>> {
+        (x, v, w)
+    } else {
+        return;
+    };
 }
 
 fn not_fire() {
@@ -298,6 +319,12 @@ fn not_fire() {
     };
 }
 
-struct S {
-    v: u32,
+struct S<T> {
+    v: T,
+}
+
+struct U<T> {
+    v: T,
+    w: T,
+    x: T,
 }

tests/ui/manual_let_else.stderr

@@ -301,13 +301,64 @@ LL |     let w = if let (Some(v), ()) = (g(), ()) { v } else { return };
    |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: consider writing: `let (Some(w), ()) = (g(), ()) else { return };`
 
 error: this could be rewritten as `let...else`
-  --> $DIR/manual_let_else.rs:275:5
+  --> $DIR/manual_let_else.rs:168:5
+   |
+LL | /     let w = if let Some(S { v: x }) = Some(S { v: 0 }) {
+LL | |         x
+LL | |     } else {
+LL | |         return;
+LL | |     };
+   | |______^
+   |
+help: consider writing
+   |
+LL ~     let Some(S { v: w }) = Some(S { v: 0 }) else {
+LL +         return;
+LL +     };
+   |
+
+error: this could be rewritten as `let...else`
+  --> $DIR/manual_let_else.rs:175:5
+   |
+LL | /     let v = if let Some(S { v: x }) = Some(S { v: 0 }) {
+LL | |         x
+LL | |     } else {
+LL | |         return;
+LL | |     };
+   | |______^
+   |
+help: consider writing
+   |
+LL ~     let Some(S { v }) = Some(S { v: 0 }) else {
+LL +         return;
+LL +     };
+   |
+
+error: this could be rewritten as `let...else`
+  --> $DIR/manual_let_else.rs:182:5
+   |
+LL | /     let (x, S { v }, w) = if let Some(U { v, w, x }) = None::<U<S<()>>> {
+LL | |         (x, v, w)
+LL | |     } else {
+LL | |         return;
+LL | |     };
+   | |______^
+   |
+help: consider writing
+   |
+LL ~     let Some(U { v: S { v }, w, x }) = None::<U<S<()>>> else {
+LL +         return;
+LL +     };
+   |
+
+error: this could be rewritten as `let...else`
+  --> $DIR/manual_let_else.rs:296:5
    |
 LL | /     let _ = match ff {
 LL | |         Some(value) => value,
 LL | |         _ => macro_call!(),
 LL | |     };
    | |______^ help: consider writing: `let Some(_) = ff else { macro_call!() };`
 
-error: aborting due to 23 previous errors
+error: aborting due to 26 previous errors