Add ExprKind::Block to type certainty algorithm

Author: samueltardieu

Diff for: clippy_utils/src/ty/type_certainty/mod.rs

@@ -110,6 +110,10 @@ fn expr_type_certainty(cx: &LateContext<'_>, expr: &Expr<'_>, in_arg: bool) -> C
 
         ExprKind::Struct(qpath, _, _) => qpath_certainty(cx, qpath, true),
 
+        ExprKind::Block(block, _) => block
+            .expr
+            .map_or(Certainty::Certain(None), |expr| expr_type_certainty(cx, expr, false)),
+
         _ => Certainty::Uncertain,
     };
 

Diff for: tests/ui/unnecessary_cast.fixed

@@ -290,4 +290,10 @@ mod fixable {
         f((1 + 2u32));
         //~^ unnecessary_cast
     }
+
+    fn with_blocks(a: i64, b: i64, c: u64) {
+        let threshold = if c < 10 { a } else { b };
+        let _ = threshold;
+        //~^ unnecessary_cast
+    }
 }

Diff for: tests/ui/unnecessary_cast.rs

@@ -290,4 +290,10 @@ mod fixable {
         f((1 + 2u32) as u32);
         //~^ unnecessary_cast
     }
+
+    fn with_blocks(a: i64, b: i64, c: u64) {
+        let threshold = if c < 10 { a } else { b };
+        let _ = threshold as i64;
+        //~^ unnecessary_cast
+    }
 }

Diff for: tests/ui/unnecessary_cast.stderr

@@ -259,5 +259,11 @@ error: casting to the same type is unnecessary (`u32` -> `u32`)
 LL |         f((1 + 2u32) as u32);
    |           ^^^^^^^^^^^^^^^^^ help: try: `(1 + 2u32)`
 
-error: aborting due to 43 previous errors
+error: casting to the same type is unnecessary (`i64` -> `i64`)
+  --> tests/ui/unnecessary_cast.rs:296:17
+   |
+LL |         let _ = threshold as i64;
+   |                 ^^^^^^^^^^^^^^^^ help: try: `threshold`
+
+error: aborting due to 44 previous errors