Suggest parentheses around if-expressions

```
error[E0308]: mismatched types
  --> $DIR/expr-as-stmt-2.rs:15:15
   |
LL |     if true { true } else { false } && true;
   |     ----------^^^^-----------------
   |     |         |
   |     |         expected `()`, found `bool`
   |     expected this to be `()`
   |
help: parentheses are required to parse this as an expression
   |
LL |     (if true { true } else { false }) && true;
   |     +                               +
```

2 files changed, 177 insertions, 2 deletions

diff --git a/tests/ui/parser/expr-as-stmt-2.rs b/tests/ui/parser/expr-as-stmt-2.rs
index 3a18bdc3b73..4b1f62d8056 100644
--- a/tests/ui/parser/expr-as-stmt-2.rs
+++ b/tests/ui/parser/expr-as-stmt-2.rs
@@ -7,4 +7,25 @@ fn foo(a: Option<u32>, b: Option<u32>) -> bool {
     if let Some(y) = a { true } else { false }
 }
 
-fn main() {}
+fn bar() -> bool {
+    false
+}
+
+fn main() {
+    if true { true } else { false } && true;
+    //~^ ERROR mismatched types
+    //~| ERROR mismatched types
+    if true { true } else { false } && if true { true } else { false };
+    //~^ ERROR mismatched types
+    //~| ERROR mismatched types
+    if true { true } else { false } if true { true } else { false };
+    //~^ ERROR mismatched types
+    //~| ERROR mismatched types
+    if true { bar() } else { bar() } && if true { bar() } else { bar() };
+    //~^ ERROR mismatched types
+    //~| ERROR mismatched types
+    if true { bar() } else { bar() } if true { bar() } else { bar() };
+    //~^ ERROR mismatched types
+    //~| ERROR mismatched types
+    let _ = if true { true } else { false } && true; // ok
+}
diff --git a/tests/ui/parser/expr-as-stmt-2.stderr b/tests/ui/parser/expr-as-stmt-2.stderr
index 2b6314c38ce..f9838ee0299 100644
--- a/tests/ui/parser/expr-as-stmt-2.stderr
+++ b/tests/ui/parser/expr-as-stmt-2.stderr
@@ -7,6 +7,10 @@ LL |     if let Some(x) = a { true } else { false }
    |     |                    expected `()`, found `bool`
    |     expected this to be `()`
    |
+help: parentheses are required to parse this as an expression
+   |
+LL |     (if let Some(x) = a { true } else { false })
+   |     +                                          +
 help: you might have meant to return this value
    |
 LL |     if let Some(x) = a { return true; } else { false }
@@ -21,6 +25,10 @@ LL |     if let Some(x) = a { true } else { false }
    |     |                                  expected `()`, found `bool`
    |     expected this to be `()`
    |
+help: parentheses are required to parse this as an expression
+   |
+LL |     (if let Some(x) = a { true } else { false })
+   |     +                                          +
 help: you might have meant to return this value
    |
 LL |     if let Some(x) = a { true } else { return false; }
@@ -41,6 +49,152 @@ help: parentheses are required to parse this as an expression
 LL |     (if let Some(x) = a { true } else { false })
    |     +                                          +
 
-error: aborting due to 3 previous errors
+error[E0308]: mismatched types
+  --> $DIR/expr-as-stmt-2.rs:15:15
+   |
+LL |     if true { true } else { false } && true;
+   |     ----------^^^^-----------------
+   |     |         |
+   |     |         expected `()`, found `bool`
+   |     expected this to be `()`
+   |
+help: parentheses are required to parse this as an expression
+   |
+LL |     (if true { true } else { false }) && true;
+   |     +                               +
+
+error[E0308]: mismatched types
+  --> $DIR/expr-as-stmt-2.rs:15:29
+   |
+LL |     if true { true } else { false } && true;
+   |     ------------------------^^^^^--
+   |     |                       |
+   |     |                       expected `()`, found `bool`
+   |     expected this to be `()`
+   |
+help: parentheses are required to parse this as an expression
+   |
+LL |     (if true { true } else { false }) && true;
+   |     +                               +
+
+error[E0308]: mismatched types
+  --> $DIR/expr-as-stmt-2.rs:18:15
+   |
+LL |     if true { true } else { false } && if true { true } else { false };
+   |     ----------^^^^-----------------
+   |     |         |
+   |     |         expected `()`, found `bool`
+   |     expected this to be `()`
+   |
+help: parentheses are required to parse this as an expression
+   |
+LL |     (if true { true } else { false }) && if true { true } else { false };
+   |     +                               +
+
+error[E0308]: mismatched types
+  --> $DIR/expr-as-stmt-2.rs:18:29
+   |
+LL |     if true { true } else { false } && if true { true } else { false };
+   |     ------------------------^^^^^--
+   |     |                       |
+   |     |                       expected `()`, found `bool`
+   |     expected this to be `()`
+   |
+help: parentheses are required to parse this as an expression
+   |
+LL |     (if true { true } else { false }) && if true { true } else { false };
+   |     +                               +
+
+error[E0308]: mismatched types
+  --> $DIR/expr-as-stmt-2.rs:21:15
+   |
+LL |     if true { true } else { false } if true { true } else { false };
+   |     ----------^^^^-----------------
+   |     |         |
+   |     |         expected `()`, found `bool`
+   |     expected this to be `()`
+
+error[E0308]: mismatched types
+  --> $DIR/expr-as-stmt-2.rs:21:29
+   |
+LL |     if true { true } else { false } if true { true } else { false };
+   |     ------------------------^^^^^--
+   |     |                       |
+   |     |                       expected `()`, found `bool`
+   |     expected this to be `()`
+
+error[E0308]: mismatched types
+  --> $DIR/expr-as-stmt-2.rs:24:15
+   |
+LL |     if true { bar() } else { bar() } && if true { bar() } else { bar() };
+   |     ----------^^^^^-----------------
+   |     |         |
+   |     |         expected `()`, found `bool`
+   |     expected this to be `()`
+   |
+help: parentheses are required to parse this as an expression
+   |
+LL |     (if true { bar() } else { bar() }) && if true { bar() } else { bar() };
+   |     +                                +
+help: consider using a semicolon here
+   |
+LL |     if true { bar() } else { bar() }; && if true { bar() } else { bar() };
+   |                                     +
+
+error[E0308]: mismatched types
+  --> $DIR/expr-as-stmt-2.rs:24:30
+   |
+LL |     if true { bar() } else { bar() } && if true { bar() } else { bar() };
+   |     -------------------------^^^^^--
+   |     |                        |
+   |     |                        expected `()`, found `bool`
+   |     expected this to be `()`
+   |
+help: parentheses are required to parse this as an expression
+   |
+LL |     (if true { bar() } else { bar() }) && if true { bar() } else { bar() };
+   |     +                                +
+help: consider using a semicolon here
+   |
+LL |     if true { bar() } else { bar() }; && if true { bar() } else { bar() };
+   |                                     +
+
+error[E0308]: mismatched types
+  --> $DIR/expr-as-stmt-2.rs:27:15
+   |
+LL |     if true { bar() } else { bar() } if true { bar() } else { bar() };
+   |     ----------^^^^^-----------------
+   |     |         |
+   |     |         expected `()`, found `bool`
+   |     expected this to be `()`
+   |
+help: consider using a semicolon here
+   |
+LL |     if true { bar(); } else { bar() } if true { bar() } else { bar() };
+   |                    +
+help: consider using a semicolon here
+   |
+LL |     if true { bar() } else { bar() }; if true { bar() } else { bar() };
+   |                                     +
+
+error[E0308]: mismatched types
+  --> $DIR/expr-as-stmt-2.rs:27:30
+   |
+LL |     if true { bar() } else { bar() } if true { bar() } else { bar() };
+   |     -------------------------^^^^^--
+   |     |                        |
+   |     |                        expected `()`, found `bool`
+   |     expected this to be `()`
+   |
+help: consider using a semicolon here
+   |
+LL |     if true { bar() } else { bar(); } if true { bar() } else { bar() };
+   |                                   +
+help: consider using a semicolon here
+   |
+LL |     if true { bar() } else { bar() }; if true { bar() } else { bar() };
+   |                                     +
+
+error: aborting due to 13 previous errors
 
 For more information about this error, try `rustc --explain E0308`.