Account for short-hand init structs when suggesting conversion

Author: estebank

src/librustc_typeck/check/demand.rs

@@ -270,7 +270,11 @@ impl<'a, 'gcx, 'tcx> FnCtxt<'a, 'gcx, 'tcx> {
         None
     }
 
-    fn is_hir_id_from_struct_pattern_shorthand_field(&self, hir_id: hir::HirId, sp: Span) -> bool {
+    crate fn is_hir_id_from_struct_pattern_shorthand_field(
+        &self,
+        hir_id: hir::HirId,
+        sp: Span,
+    ) -> bool {
         let cm = self.sess().source_map();
         let parent_id = self.tcx.hir().get_parent_node_by_hir_id(hir_id);
         if let Some(parent) = self.tcx.hir().find_by_hir_id(parent_id) {

src/librustc_typeck/check/mod.rs

@@ -5014,6 +5014,10 @@ impl<'a, 'gcx, 'tcx> FnCtxt<'a, 'gcx, 'tcx> {
                 Applicability::MachineApplicable,
             );
         } else if !self.check_for_cast(err, expr, found, expected) {
+            let is_struct_pat_shorthand_field = self.is_hir_id_from_struct_pattern_shorthand_field(
+                expr.hir_id,
+                expr.span,
+            );
             let methods = self.get_conversion_methods(expr.span, expected, found);
             if let Ok(expr_text) = self.sess().source_map().span_to_snippet(expr.span) {
                 let mut suggestions = iter::repeat(&expr_text).zip(methods.iter())
@@ -5023,14 +5027,18 @@ impl<'a, 'gcx, 'tcx> FnCtxt<'a, 'gcx, 'tcx> {
                             None  // do not suggest code that is already there (#53348)
                         } else {
                             let method_call_list = [".to_vec()", ".to_string()"];
-                            if receiver.ends_with(".clone()")
+                            let sugg = if receiver.ends_with(".clone()")
                                     && method_call_list.contains(&method_call.as_str()) {
                                 let max_len = receiver.rfind(".").unwrap();
-                                Some(format!("{}{}", &receiver[..max_len], method_call))
-                            }
-                            else {
-                                Some(format!("{}{}", receiver, method_call))
-                            }
+                                format!("{}{}", &receiver[..max_len], method_call)
+                            } else {
+                                format!("{}{}", receiver, method_call)
+                            };
+                            Some(if is_struct_pat_shorthand_field {
+                                format!("{}: {}", receiver, sugg)
+                            } else {
+                                sugg
+                            })
                         }
                     }).peekable();
                 if suggestions.peek().is_some() {

src/test/ui/suggestions/issue-52820.rs

@@ -0,0 +1,12 @@
+struct Bravery {
+    guts: String,
+    brains: String,
+}
+
+fn main() {
+    let guts = "mettle";
+    let _ = Bravery {
+        guts, //~ ERROR mismatched types
+        brains: guts.clone(), //~ ERROR mismatched types
+    };
+}

src/test/ui/suggestions/issue-52820.stderr

@@ -0,0 +1,27 @@
+error[E0308]: mismatched types
+  --> $DIR/issue-52820.rs:9:9
+   |
+LL |         guts,
+   |         ^^^^
+   |         |
+   |         expected struct `std::string::String`, found &str
+   |         help: try using a conversion method: `guts: guts.to_string()`
+   |
+   = note: expected type `std::string::String`
+              found type `&str`
+
+error[E0308]: mismatched types
+  --> $DIR/issue-52820.rs:10:17
+   |
+LL |         brains: guts.clone(),
+   |                 ^^^^^^^^^^^^
+   |                 |
+   |                 expected struct `std::string::String`, found &str
+   |                 help: try using a conversion method: `guts.to_string()`
+   |
+   = note: expected type `std::string::String`
+              found type `&str`
+
+error: aborting due to 2 previous errors
+
+For more information about this error, try `rustc --explain E0308`.