Auto merge of #11020 - Centri3:tuple_array_conversion, r=llogiq

New lint [`tuple_array_conversions`]

Closes #10748

PS, the implementation is a bit ugly 😅 ~~I will likely refactor soon enough :)~~ Done :D

changelog: New lint [`tuple_array_conversions`]

tests/ui/tuple_array_conversions.rs

@@ -0,0 +1,73 @@
+//@aux-build:proc_macros.rs:proc-macro
+#![allow(clippy::no_effect, clippy::useless_vec, unused)]
+#![warn(clippy::tuple_array_conversions)]
+
+#[macro_use]
+extern crate proc_macros;
+
+fn main() {
+    let x = [1, 2];
+    let x = (x[0], x[1]);
+    let x = [x.0, x.1];
+    let x = &[1, 2];
+    let x = (x[0], x[1]);
+
+    let t1: &[(u32, u32)] = &[(1, 2), (3, 4)];
+    let v1: Vec<[u32; 2]> = t1.iter().map(|&(a, b)| [a, b]).collect();
+    t1.iter().for_each(|&(a, b)| _ = [a, b]);
+    let t2: Vec<(u32, u32)> = v1.iter().map(|&[a, b]| (a, b)).collect();
+    t1.iter().for_each(|&(a, b)| _ = [a, b]);
+    // Do not lint
+    let v2: Vec<[u32; 2]> = t1.iter().map(|&t| t.into()).collect();
+    let t3: Vec<(u32, u32)> = v2.iter().map(|&v| v.into()).collect();
+    let x = [1; 13];
+    let x = (
+        x[0], x[1], x[2], x[3], x[4], x[5], x[6], x[7], x[8], x[9], x[10], x[11], x[12],
+    );
+    let x = [x.0, x.1, x.2, x.3, x.4, x.5, x.6, x.7, x.8, x.9, x.10, x.11, x.12];
+    let x = (1, 2);
+    let x = (x.0, x.1);
+    let x = [1, 2];
+    let x = [x[0], x[1]];
+    let x = vec![1, 2];
+    let x = (x[0], x[1]);
+    let x = [1; 3];
+    let x = (x[0],);
+    let x = (1, 2, 3);
+    let x = [x.0];
+    let x = (1, 2);
+    let y = (1, 2);
+    [x.0, y.0];
+    [x.0, y.1];
+    let x = [x.0, x.0];
+    let x = (x[0], x[0]);
+    external! {
+        let t1: &[(u32, u32)] = &[(1, 2), (3, 4)];
+        let v1: Vec<[u32; 2]> = t1.iter().map(|&(a, b)| [a, b]).collect();
+        let t2: Vec<(u32, u32)> = v1.iter().map(|&[a, b]| (a, b)).collect();
+    }
+    with_span! {
+        span
+        let t1: &[(u32, u32)] = &[(1, 2), (3, 4)];
+        let v1: Vec<[u32; 2]> = t1.iter().map(|&(a, b)| [a, b]).collect();
+        let t2: Vec<(u32, u32)> = v1.iter().map(|&[a, b]| (a, b)).collect();
+    }
+}
+
+#[clippy::msrv = "1.70.0"]
+fn msrv_too_low() {
+    let x = [1, 2];
+    let x = (x[0], x[1]);
+    let x = [x.0, x.1];
+    let x = &[1, 2];
+    let x = (x[0], x[1]);
+}
+
+#[clippy::msrv = "1.71.0"]
+fn msrv_juust_right() {
+    let x = [1, 2];
+    let x = (x[0], x[1]);
+    let x = [x.0, x.1];
+    let x = &[1, 2];
+    let x = (x[0], x[1]);
+}

tests/ui/tuple_array_conversions.stderr

@@ -0,0 +1,83 @@
+error: it looks like you're trying to convert an array to a tuple
+  --> $DIR/tuple_array_conversions.rs:10:13
+   |
+LL |     let x = (x[0], x[1]);
+   |             ^^^^^^^^^^^^
+   |
+   = help: use `.into()` instead, or `<(T0, T1, ..., Tn)>::from` if type annotations are needed
+   = note: `-D clippy::tuple-array-conversions` implied by `-D warnings`
+
+error: it looks like you're trying to convert a tuple to an array
+  --> $DIR/tuple_array_conversions.rs:11:13
+   |
+LL |     let x = [x.0, x.1];
+   |             ^^^^^^^^^^
+   |
+   = help: use `.into()` instead, or `<[T; N]>::from` if type annotations are needed
+
+error: it looks like you're trying to convert an array to a tuple
+  --> $DIR/tuple_array_conversions.rs:13:13
+   |
+LL |     let x = (x[0], x[1]);
+   |             ^^^^^^^^^^^^
+   |
+   = help: use `.into()` instead, or `<(T0, T1, ..., Tn)>::from` if type annotations are needed
+
+error: it looks like you're trying to convert a tuple to an array
+  --> $DIR/tuple_array_conversions.rs:16:53
+   |
+LL |     let v1: Vec<[u32; 2]> = t1.iter().map(|&(a, b)| [a, b]).collect();
+   |                                                     ^^^^^^
+   |
+   = help: use `.into()` instead, or `<[T; N]>::from` if type annotations are needed
+
+error: it looks like you're trying to convert a tuple to an array
+  --> $DIR/tuple_array_conversions.rs:17:38
+   |
+LL |     t1.iter().for_each(|&(a, b)| _ = [a, b]);
+   |                                      ^^^^^^
+   |
+   = help: use `.into()` instead, or `<[T; N]>::from` if type annotations are needed
+
+error: it looks like you're trying to convert an array to a tuple
+  --> $DIR/tuple_array_conversions.rs:18:55
+   |
+LL |     let t2: Vec<(u32, u32)> = v1.iter().map(|&[a, b]| (a, b)).collect();
+   |                                                       ^^^^^^
+   |
+   = help: use `.into()` instead, or `<(T0, T1, ..., Tn)>::from` if type annotations are needed
+
+error: it looks like you're trying to convert a tuple to an array
+  --> $DIR/tuple_array_conversions.rs:19:38
+   |
+LL |     t1.iter().for_each(|&(a, b)| _ = [a, b]);
+   |                                      ^^^^^^
+   |
+   = help: use `.into()` instead, or `<[T; N]>::from` if type annotations are needed
+
+error: it looks like you're trying to convert an array to a tuple
+  --> $DIR/tuple_array_conversions.rs:69:13
+   |
+LL |     let x = (x[0], x[1]);
+   |             ^^^^^^^^^^^^
+   |
+   = help: use `.into()` instead, or `<(T0, T1, ..., Tn)>::from` if type annotations are needed
+
+error: it looks like you're trying to convert a tuple to an array
+  --> $DIR/tuple_array_conversions.rs:70:13
+   |
+LL |     let x = [x.0, x.1];
+   |             ^^^^^^^^^^
+   |
+   = help: use `.into()` instead, or `<[T; N]>::from` if type annotations are needed
+
+error: it looks like you're trying to convert an array to a tuple
+  --> $DIR/tuple_array_conversions.rs:72:13
+   |
+LL |     let x = (x[0], x[1]);
+   |             ^^^^^^^^^^^^
+   |
+   = help: use `.into()` instead, or `<(T0, T1, ..., Tn)>::from` if type annotations are needed
+
+error: aborting due to 10 previous errors
+