Auto merge of #10350 - J-ZhengLi:issue_10272, r=xFrednet

enhance [`ifs_same_cond`] to warn same immutable method calls as well

fixes: #10272

---

changelog: Enhancement: [`ifs_same_cond`]: Now also detects immutable method calls.
[#10350](https://github.com/rust-lang/rust-clippy/pull/10350)
<!-- changelog_checked -->

tests/ui-toml/ifs_same_cond/clippy.toml

@@ -0,0 +1 @@
+ignore-interior-mutability = ["std::cell::Cell"]

tests/ui-toml/ifs_same_cond/ifs_same_cond.rs

@@ -0,0 +1,18 @@
+#![warn(clippy::ifs_same_cond)]
+#![allow(clippy::if_same_then_else, clippy::comparison_chain)]
+
+fn main() {}
+
+fn issue10272() {
+    use std::cell::Cell;
+
+    // Because the `ignore-interior-mutability` configuration
+    // is set to ignore for `std::cell::Cell`, the following `get()` calls
+    // should trigger warning
+    let x = Cell::new(true);
+    if x.get() {
+    } else if !x.take() {
+    } else if x.get() {
+    } else {
+    }
+}

tests/ui-toml/ifs_same_cond/ifs_same_cond.stderr

@@ -0,0 +1,15 @@
+error: this `if` has the same condition as a previous `if`
+  --> $DIR/ifs_same_cond.rs:15:15
+   |
+LL |     } else if x.get() {
+   |               ^^^^^^^
+   |
+note: same as this
+  --> $DIR/ifs_same_cond.rs:13:8
+   |
+LL |     if x.get() {
+   |        ^^^^^^^
+   = note: `-D clippy::ifs-same-cond` implied by `-D warnings`
+
+error: aborting due to previous error
+

tests/ui/ifs_same_cond.rs

@@ -43,4 +43,30 @@ fn ifs_same_cond() {
     }
 }
 
+fn issue10272() {
+    let a = String::from("ha");
+    if a.contains("ah") {
+    } else if a.contains("ah") {
+        // Trigger this lint
+    } else if a.contains("ha") {
+    } else if a == "wow" {
+    }
+
+    let p: *mut i8 = std::ptr::null_mut();
+    if p.is_null() {
+    } else if p.align_offset(0) == 0 {
+    } else if p.is_null() {
+        // ok, p is mutable pointer
+    } else {
+    }
+
+    let x = std::cell::Cell::new(true);
+    if x.get() {
+    } else if !x.take() {
+    } else if x.get() {
+        // ok, x is interior mutable type
+    } else {
+    }
+}
+
 fn main() {}

tests/ui/ifs_same_cond.stderr

@@ -35,5 +35,17 @@ note: same as this
 LL |     if 2 * a == 1 {
    |        ^^^^^^^^^^
 
-error: aborting due to 3 previous errors
+error: this `if` has the same condition as a previous `if`
+  --> $DIR/ifs_same_cond.rs:49:15
+   |
+LL |     } else if a.contains("ah") {
+   |               ^^^^^^^^^^^^^^^^
+   |
+note: same as this
+  --> $DIR/ifs_same_cond.rs:48:8
+   |
+LL |     if a.contains("ah") {
+   |        ^^^^^^^^^^^^^^^^
+
+error: aborting due to 4 previous errors