Include `let` assignment in suggestion

Placeholders are still given for the content of the whole block. However, if the
result of the original `if let` or `match` expression was assigned, the
assignment is reflected in the suggestion.

No-op assignments (`let x = x;`) are skipped though, unless they contain an
explicit type which might help the compiler (`let x: u32 = x;` is kept).

2 files changed, 206 insertions, 2 deletions

diff --git a/tests/ui/while_let_loop.rs b/tests/ui/while_let_loop.rs
index d591ab984cf..95062c9f46c 100644
--- a/tests/ui/while_let_loop.rs
+++ b/tests/ui/while_let_loop.rs
@@ -154,3 +154,89 @@ fn issue_5715(mut m: core::cell::RefCell<Option<u32>>) {
         m = core::cell::RefCell::new(Some(x + 1));
     }
 }
+
+mod issue_362 {
+    pub fn merge_sorted<T>(xs: Vec<T>, ys: Vec<T>) -> Vec<T>
+    where
+        T: PartialOrd,
+    {
+        let total_len = xs.len() + ys.len();
+        let mut res = Vec::with_capacity(total_len);
+        let mut ix = xs.into_iter().peekable();
+        let mut iy = ys.into_iter().peekable();
+        loop {
+            //~^ while_let_loop
+            let lt = match (ix.peek(), iy.peek()) {
+                (Some(x), Some(y)) => x < y,
+                _ => break,
+            };
+            res.push(if lt { &mut ix } else { &mut iy }.next().unwrap());
+        }
+        res.extend(ix);
+        res.extend(iy);
+        res
+    }
+}
+
+fn let_assign() {
+    loop {
+        //~^ while_let_loop
+        let x = if let Some(y) = Some(3) {
+            y
+        } else {
+            break;
+        };
+        if x == 3 {
+            break;
+        }
+    }
+
+    loop {
+        //~^ while_let_loop
+        let x: u32 = if let Some(y) = Some(3) {
+            y
+        } else {
+            break;
+        };
+        if x == 3 {
+            break;
+        }
+    }
+
+    loop {
+        //~^ while_let_loop
+        let x = if let Some(x) = Some(3) {
+            x
+        } else {
+            break;
+        };
+        if x == 3 {
+            break;
+        }
+    }
+
+    loop {
+        //~^ while_let_loop
+        let x: u32 = if let Some(x) = Some(3) {
+            x
+        } else {
+            break;
+        };
+        if x == 3 {
+            break;
+        }
+    }
+
+    loop {
+        //~^ while_let_loop
+        let x = if let Some(x) = Some(2) {
+            let t = 1;
+            t + x
+        } else {
+            break;
+        };
+        if x == 3 {
+            break;
+        }
+    }
+}
diff --git a/tests/ui/while_let_loop.stderr b/tests/ui/while_let_loop.stderr
index bd482857e67..ed42628a53e 100644
--- a/tests/ui/while_let_loop.stderr
+++ b/tests/ui/while_let_loop.stderr
@@ -57,7 +57,125 @@ LL | |         let (e, l) = match "".split_whitespace().next() {
 ...  |
 LL | |         let _ = (e, l);
 LL | |     }
-   | |_____^ help: try: `while let Some(word) = "".split_whitespace().next() { .. }`
+   | |_____^
+   |
+help: try
+   |
+LL ~     while let Some(word) = "".split_whitespace().next() {
+LL +         let (e, l) = (word.is_empty(), word.len());
+LL +         ..
+LL +     }
+   |
+
+error: this loop could be written as a `while let` loop
+  --> tests/ui/while_let_loop.rs:167:9
+   |
+LL | /         loop {
+LL | |
+LL | |             let lt = match (ix.peek(), iy.peek()) {
+LL | |                 (Some(x), Some(y)) => x < y,
+...  |
+LL | |             res.push(if lt { &mut ix } else { &mut iy }.next().unwrap());
+LL | |         }
+   | |_________^
+   |
+help: try
+   |
+LL ~         while let (Some(x), Some(y)) = (ix.peek(), iy.peek()) {
+LL +             let lt = x < y;
+LL +             ..
+LL +         }
+   |
+
+error: this loop could be written as a `while let` loop
+  --> tests/ui/while_let_loop.rs:182:5
+   |
+LL | /     loop {
+LL | |
+LL | |         let x = if let Some(y) = Some(3) {
+LL | |             y
+...  |
+LL | |     }
+   | |_____^
+   |
+help: try
+   |
+LL ~     while let Some(y) = Some(3) {
+LL +         let x = y;
+LL +         ..
+LL +     }
+   |
+
+error: this loop could be written as a `while let` loop
+  --> tests/ui/while_let_loop.rs:194:5
+   |
+LL | /     loop {
+LL | |
+LL | |         let x: u32 = if let Some(y) = Some(3) {
+LL | |             y
+...  |
+LL | |     }
+   | |_____^
+   |
+help: try
+   |
+LL ~     while let Some(y) = Some(3) {
+LL +         let x: u32 = y;
+LL +         ..
+LL +     }
+   |
+
+error: this loop could be written as a `while let` loop
+  --> tests/ui/while_let_loop.rs:206:5
+   |
+LL | /     loop {
+LL | |
+LL | |         let x = if let Some(x) = Some(3) {
+LL | |             x
+...  |
+LL | |     }
+   | |_____^ help: try: `while let Some(x) = Some(3) { .. }`
+
+error: this loop could be written as a `while let` loop
+  --> tests/ui/while_let_loop.rs:218:5
+   |
+LL | /     loop {
+LL | |
+LL | |         let x: u32 = if let Some(x) = Some(3) {
+LL | |             x
+...  |
+LL | |     }
+   | |_____^
+   |
+help: try
+   |
+LL ~     while let Some(x) = Some(3) {
+LL +         let x: u32 = x;
+LL +         ..
+LL +     }
+   |
+
+error: this loop could be written as a `while let` loop
+  --> tests/ui/while_let_loop.rs:230:5
+   |
+LL | /     loop {
+LL | |
+LL | |         let x = if let Some(x) = Some(2) {
+LL | |             let t = 1;
+...  |
+LL | |     }
+   | |_____^
+   |
+help: try
+   |
+LL ~     while let Some(x) = Some(2) {
+LL +         let x = {
+LL +             let t = 1;
+LL +             t + x
+LL +         };
+LL +         ..
+LL +     }
+   |
 
-error: aborting due to 5 previous errors
+error: aborting due to 11 previous errors