Suggest better place to add call parentheses for method expressions wrapped in parentheses

Author: Kobzol

compiler/rustc_typeck/src/check/expr.rs

@@ -1844,6 +1844,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                 field,
                 expr_t,
                 expr,
+                None,
             );
         }
         err.emit();
@@ -1870,9 +1871,11 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
             };
         let expr_snippet =
             self.tcx.sess.source_map().span_to_snippet(expr.span).unwrap_or(String::new());
-        if expr_is_call && expr_snippet.starts_with("(") && expr_snippet.ends_with(")") {
-            let after_open = expr.span.lo() + rustc_span::BytePos(1);
-            let before_close = expr.span.hi() - rustc_span::BytePos(1);
+        let is_wrapped = expr_snippet.starts_with("(") && expr_snippet.ends_with(")");
+        let after_open = expr.span.lo() + rustc_span::BytePos(1);
+        let before_close = expr.span.hi() - rustc_span::BytePos(1);
+
+        if expr_is_call && is_wrapped {
             err.multipart_suggestion(
                 "remove wrapping parentheses to call the method",
                 vec![
@@ -1882,12 +1885,19 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                 Applicability::MachineApplicable,
             );
         } else if !self.expr_in_place(expr.hir_id) {
+            // Suggest call parentheses inside the wrapping parentheses
+            let span = if is_wrapped {
+                expr.span.with_lo(after_open).with_hi(before_close)
+            } else {
+                expr.span
+            };
             self.suggest_method_call(
                 &mut err,
                 "use parentheses to call the method",
                 field,
                 expr_t,
                 expr,
+                Some(span),
             );
         } else {
             err.help("methods are immutable and cannot be assigned to");

compiler/rustc_typeck/src/check/method/mod.rs

@@ -141,6 +141,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
         method_name: Ident,
         self_ty: Ty<'tcx>,
         call_expr: &hir::Expr<'_>,
+        span: Option<Span>,
     ) {
         let params = self
             .probe_for_name(
@@ -159,7 +160,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
             .unwrap_or(0);
 
         // Account for `foo.bar<T>`;
-        let sugg_span = call_expr.span.shrink_to_hi();
+        let sugg_span = span.unwrap_or_else(|| call_expr.span).shrink_to_hi();
         let (suggestion, applicability) = (
             format!("({})", (0..params).map(|_| "_").collect::<Vec<_>>().join(", ")),
             if params > 0 { Applicability::HasPlaceholders } else { Applicability::MaybeIncorrect },

src/test/ui/typeck/issue-89044-wrapped-expr-method.fixed

@@ -0,0 +1,9 @@
+// run-rustfix
+
+fn main() {
+    let a = Some(42);
+    println!(
+        "The value is {}.",
+        (a.unwrap()) //~ERROR [E0615]
+    );
+}

src/test/ui/typeck/issue-89044-wrapped-expr-method.rs

@@ -0,0 +1,9 @@
+// run-rustfix
+
+fn main() {
+    let a = Some(42);
+    println!(
+        "The value is {}.",
+        (a.unwrap) //~ERROR [E0615]
+    );
+}

src/test/ui/typeck/issue-89044-wrapped-expr-method.stderr

@@ -0,0 +1,14 @@
+error[E0615]: attempted to take value of method `unwrap` on type `Option<{integer}>`
+  --> $DIR/issue-89044-wrapped-expr-method.rs:7:12
+   |
+LL |         (a.unwrap)
+   |            ^^^^^^ method, not a field
+   |
+help: use parentheses to call the method
+   |
+LL |         (a.unwrap())
+   |                  ++
+
+error: aborting due to previous error
+
+For more information about this error, try `rustc --explain E0615`.