Add suggestions for misspelled method names

Use the syntax::util::lev_distance module to provide suggestions when a
named method cannot be found.

Part of #30197

src/test/ui/block-result/issue-3563.stderr

@@ -3,6 +3,8 @@ error[E0599]: no method named `b` found for type `&Self` in the current scope
    |
 13 |         || self.b()
    |                 ^
+   |
+   = help: did you mean `a`?
 
 error[E0308]: mismatched types
   --> $DIR/issue-3563.rs:13:9

src/test/ui/suggestions/suggest-methods.rs

@@ -0,0 +1,38 @@
+// Copyright 2017 The Rust Project Developers. See the COPYRIGHT
+// file at the top-level directory of this distribution and at
+// http://rust-lang.org/COPYRIGHT.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+struct Foo;
+
+impl Foo {
+    fn bar(self) {}
+    fn baz(&self, x: f64) {}
+}
+
+trait FooT {
+    fn bag(&self);
+}
+
+impl FooT for Foo {
+    fn bag(&self) {}
+}
+
+fn main() {
+    let f = Foo;
+    f.bat(1.0);
+
+    let s = "foo".to_string();
+    let _ = s.is_emtpy();
+
+    // Generates a warning, both for count_ones and count_zeros
+    let _ = 63u32.count_eos();
+    let _ = 63u32.count_o(); // Does not generate a warning
+
+}
+

src/test/ui/suggestions/suggest-methods.stderr

@@ -0,0 +1,34 @@
+error[E0599]: no method named `bat` found for type `Foo` in the current scope
+  --> $DIR/suggest-methods.rs:28:7
+   |
+28 |     f.bat(1.0);
+   |       ^^^
+   |
+   = help: did you mean `bar`?
+   = help: did you mean `baz`?
+
+error[E0599]: no method named `is_emtpy` found for type `std::string::String` in the current scope
+  --> $DIR/suggest-methods.rs:31:15
+   |
+31 |     let _ = s.is_emtpy();
+   |               ^^^^^^^^
+   |
+   = help: did you mean `is_empty`?
+
+error[E0599]: no method named `count_eos` found for type `u32` in the current scope
+  --> $DIR/suggest-methods.rs:34:19
+   |
+34 |     let _ = 63u32.count_eos();
+   |                   ^^^^^^^^^
+   |
+   = help: did you mean `count_ones`?
+   = help: did you mean `count_zeros`?
+
+error[E0599]: no method named `count_o` found for type `u32` in the current scope
+  --> $DIR/suggest-methods.rs:35:19
+   |
+35 |     let _ = 63u32.count_o(); // Does not generate a warning
+   |                   ^^^^^^^
+
+error: aborting due to 4 previous errors
+