Add more tests

Author: varkor

src/test/ui/inference/infer-binary-operand-behind-reference.rs

@@ -1,6 +1,8 @@
 // check-pass
 
 fn main() {
+    // Test that we can infer the type of binary operands when
+    // references are involved, on various types and operators.
     let _: u8 = 0 + 0;
     let _: u8 = 0 + &0;
     let _: u8 = &0 + 0;
@@ -10,4 +12,19 @@ fn main() {
     let _: f32 = 0.0 + &0.0;
     let _: f32 = &0.0 + 0.0;
     let _: f32 = &0.0 + &0.0;
+
+    let _: u8 = 0 << 0;
+    let _: u8 = 0 << &0;
+    let _: u8 = &0 << 0;
+    let _: u8 = &0 << &0;
+
+    // Test type inference when variable types are indirectly inferred.
+    let a = 22;
+    let _: usize = a + &44;
+
+    // When we have no expected type, the types of the operands is the default type.
+    let _ = 0 + 0;
+    let _ = 0 + &0;
+    let _ = &0 + 0;
+    let _ = &0 + &0;
 }