Auto merge of rust-lang#11214 - y21:issue11213, r=Jarcho

check that the types are equal in `SpanlessEq::eq_expr`

Fixes rust-lang#11213

changelog: [`if_same_then_else`]: don't lint for integer literals of different types

Author: bors

clippy_utils/src/hir_utils.rs

@@ -252,15 +252,15 @@ impl HirEqInterExpr<'_, '_, '_> {
             return false;
         }
 
-        if let Some((typeck_lhs, typeck_rhs)) = self.inner.maybe_typeck_results {
-            if let (Some(l), Some(r)) = (
+        if let Some((typeck_lhs, typeck_rhs)) = self.inner.maybe_typeck_results
+            && typeck_lhs.expr_ty(left) == typeck_rhs.expr_ty(right)
+            && let (Some(l), Some(r)) = (
                 constant_simple(self.inner.cx, typeck_lhs, left),
                 constant_simple(self.inner.cx, typeck_rhs, right),
-            ) {
-                if l == r {
-                    return true;
-                }
-            }
+            )
+            && l == r
+        {
+            return true;
         }
 
         let is_eq = match (

tests/ui/if_same_then_else.rs

@@ -214,4 +214,45 @@ mod issue_8836 {
     }
 }
 
+mod issue_11213 {
+    fn reproducer(x: bool) -> bool {
+        if x {
+            0_u8.is_power_of_two()
+        } else {
+            0_u16.is_power_of_two()
+        }
+    }
+
+    // a more obvious reproducer that shows
+    // why the code above is problematic:
+    fn v2(x: bool) -> bool {
+        trait Helper {
+            fn is_u8(&self) -> bool;
+        }
+        impl Helper for u8 {
+            fn is_u8(&self) -> bool {
+                true
+            }
+        }
+        impl Helper for u16 {
+            fn is_u8(&self) -> bool {
+                false
+            }
+        }
+
+        // this is certainly not the same code in both branches
+        // it returns a different bool depending on the branch.
+        if x { 0_u8.is_u8() } else { 0_u16.is_u8() }
+    }
+
+    fn do_lint(x: bool) -> bool {
+        // but do lint if the type of the literal is the same
+        if x {
+            0_u8.is_power_of_two()
+        } else {
+            0_u8.is_power_of_two()
+        }
+    }
+}
+
 fn main() {}

tests/ui/if_same_then_else.stderr

@@ -108,5 +108,23 @@ LL | |         bar + 1;
 LL | |     }
    | |_____^
 
-error: aborting due to 5 previous errors
+error: this `if` has identical blocks
+  --> $DIR/if_same_then_else.rs:250:14
+   |
+LL |           if x {
+   |  ______________^
+LL | |             0_u8.is_power_of_two()
+LL | |         } else {
+   | |_________^
+   |
+note: same as this
+  --> $DIR/if_same_then_else.rs:252:16
+   |
+LL |           } else {
+   |  ________________^
+LL | |             0_u8.is_power_of_two()
+LL | |         }
+   | |_________^
+
+error: aborting due to 6 previous errors