Merge pull request #360 from Manishearth/fix-ice

Fix a panic caused by while let

Cargo.toml

@@ -1,6 +1,6 @@
 [package]
 name = "clippy"
-version = "0.0.17"
+version = "0.0.18"
 authors = [
 	"Manish Goregaokar <manishsmail@gmail.com>",
 	"Andre Bogus <bogusandre@gmail.com>",

src/loops.rs

@@ -312,7 +312,7 @@ fn is_iterable_array(ty: ty::Ty) -> bool {
 fn extract_expr_from_first_stmt(block: &Block) -> Option<&Expr> {
     match block.expr {
         Some(_) => None,
-        None => match block.stmts[0].node {
+        None if !block.stmts.is_empty() => match block.stmts[0].node {
             StmtDecl(ref decl, _) => match decl.node {
                 DeclLocal(ref local) => match local.init {
                     Some(ref expr) => Some(expr),
@@ -322,6 +322,7 @@ fn extract_expr_from_first_stmt(block: &Block) -> Option<&Expr> {
             },
             _ => None,
         },
+        _ => None,
     }
 }
 
@@ -329,10 +330,11 @@ fn extract_expr_from_first_stmt(block: &Block) -> Option<&Expr> {
 fn extract_first_expr(block: &Block) -> Option<&Expr> {
     match block.expr {
         Some(ref expr) => Some(expr),
-        None => match block.stmts[0].node {
+        None if !block.stmts.is_empty() => match block.stmts[0].node {
             StmtExpr(ref expr, _) | StmtSemi(ref expr, _) => Some(expr),
             _ => None,
         },
+        _ => None,
     }
 }
 

tests/compile-fail/while_loop.rs

@@ -1,7 +1,9 @@
 #![feature(plugin)]
 #![plugin(clippy)]
 
-#[deny(while_let_loop)]
+#![deny(while_let_loop)]
+#![allow(dead_code, unused)]
+
 fn main() {
     let y = Some(true);
     loop { //~ERROR
@@ -44,3 +46,18 @@ fn main() {
         println!("{}", x);
     }
 }
+
+// regression test (#360)
+// this should not panic
+// it's okay if further iterations of the lint
+// cause this function to trigger it
+fn no_panic<T>(slice: &[T]) {
+    let mut iter = slice.iter();
+    loop {
+        let _ = match iter.next() {
+            Some(ele) => ele,
+            None => break
+        };
+        loop {}
+    }
+}