Fix suggestion for Option to bool with proper precedence handling

compiler/rustc_hir_typeck/src/fn_ctxt/suggestions.rs

@@ -1692,12 +1692,18 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
         }
 
         let suggestion = match self.tcx.hir_maybe_get_struct_pattern_shorthand_field(expr) {
-            Some(ident) => format!(": {ident}.is_some()"),
-            None => ".is_some()".to_string(),
+            Some(ident) => vec![(expr.span.shrink_to_hi(), format!(": {ident}.is_some()"))],
+            None if self.precedence(expr) < ExprPrecedence::Unambiguous => {
+                // Apply the method to the whole expression, e.g. `(*value).is_some()`.
+                vec![
+                    (expr.span.shrink_to_lo(), "(".to_string()),
+                    (expr.span.shrink_to_hi(), ").is_some()".to_string()),
+                ]
+            }
+            None => vec![(expr.span.shrink_to_hi(), ".is_some()".to_string())],
         };
 
-        diag.span_suggestion_verbose(
-            expr.span.shrink_to_hi(),
+        diag.multipart_suggestion(
             "use `Option::is_some` to test if the `Option` has a value",
             suggestion,
             Applicability::MachineApplicable,

tests/ui/suggestions/option-to-bool.fixed

@@ -0,0 +1,35 @@
+// An `is_some()` suggestion must apply to the whole expression, preserving its precedence.
+//@ run-rustfix
+
+fn foo(x: Option<i32>) {
+    if true && x.is_some() {}
+    //~^ ERROR mismatched types
+    //~| HELP use `Option::is_some` to test if the `Option` has a value
+
+    let reference = &x;
+    if (*reference).is_some() {}
+    //~^ ERROR mismatched types
+    //~| HELP use `Option::is_some` to test if the `Option` has a value
+
+    if (&x).is_some() {}
+    //~^ ERROR mismatched types
+    //~| HELP use `Option::is_some` to test if the `Option` has a value
+
+    if (Value + Value).is_some() {}
+    //~^ ERROR mismatched types
+    //~| HELP use `Option::is_some` to test if the `Option` has a value
+}
+
+struct Value;
+
+impl std::ops::Add for Value {
+    type Output = Option<i32>;
+
+    fn add(self, _: Self) -> Self::Output {
+        Some(1)
+    }
+}
+
+fn main() {
+    foo(Some(1));
+}

tests/ui/suggestions/option-to-bool.rs

@@ -1,7 +1,35 @@
+// An `is_some()` suggestion must apply to the whole expression, preserving its precedence.
+//@ run-rustfix
+
 fn foo(x: Option<i32>) {
     if true && x {}
     //~^ ERROR mismatched types
     //~| HELP use `Option::is_some` to test if the `Option` has a value
+
+    let reference = &x;
+    if *reference {}
+    //~^ ERROR mismatched types
+    //~| HELP use `Option::is_some` to test if the `Option` has a value
+
+    if &x {}
+    //~^ ERROR mismatched types
+    //~| HELP use `Option::is_some` to test if the `Option` has a value
+
+    if Value + Value {}
+    //~^ ERROR mismatched types
+    //~| HELP use `Option::is_some` to test if the `Option` has a value
 }
 
-fn main() {}
+struct Value;
+
+impl std::ops::Add for Value {
+    type Output = Option<i32>;
+
+    fn add(self, _: Self) -> Self::Output {
+        Some(1)
+    }
+}
+
+fn main() {
+    foo(Some(1));
+}

tests/ui/suggestions/option-to-bool.stderr

@@ -1,5 +1,5 @@
 error[E0308]: mismatched types
-  --> $DIR/option-to-bool.rs:2:16
+  --> $DIR/option-to-bool.rs:5:16
    |
 LL |     if true && x {}
    |        ----    ^ expected `bool`, found `Option<i32>`
@@ -13,6 +13,45 @@ help: use `Option::is_some` to test if the `Option` has a value
 LL |     if true && x.is_some() {}
    |                 ++++++++++
 
-error: aborting due to 1 previous error
+error[E0308]: mismatched types
+  --> $DIR/option-to-bool.rs:10:8
+   |
+LL |     if *reference {}
+   |        ^^^^^^^^^^ expected `bool`, found `Option<i32>`
+   |
+   = note: expected type `bool`
+              found enum `Option<i32>`
+help: use `Option::is_some` to test if the `Option` has a value
+   |
+LL |     if (*reference).is_some() {}
+   |        +          +++++++++++
+
+error[E0308]: mismatched types
+  --> $DIR/option-to-bool.rs:14:8
+   |
+LL |     if &x {}
+   |        ^^ expected `bool`, found `&Option<i32>`
+   |
+   = note:   expected type `bool`
+           found reference `&Option<i32>`
+help: use `Option::is_some` to test if the `Option` has a value
+   |
+LL |     if (&x).is_some() {}
+   |        +  +++++++++++
+
+error[E0308]: mismatched types
+  --> $DIR/option-to-bool.rs:18:8
+   |
+LL |     if Value + Value {}
+   |        ^^^^^^^^^^^^^ expected `bool`, found `Option<i32>`
+   |
+   = note: expected type `bool`
+              found enum `Option<i32>`
+help: use `Option::is_some` to test if the `Option` has a value
+   |
+LL |     if (Value + Value).is_some() {}
+   |        +             +++++++++++
+
+error: aborting due to 4 previous errors
 
 For more information about this error, try `rustc --explain E0308`.