Auto merge of rust-lang#140748 - m-ou-se:super-format-args3, r=jdonszelmann

 Allow storing `format_args!()` in variable

Fixes rust-lang#92698

Tracking issue for super let: rust-lang#139076

Tracking issue for format_args: rust-lang#99012

This change allows:

```rust
let name = "world";
let f = format_args!("hello {name}!"); // New: Store format_args!() for later!

println!("{f}");
```

This will need an FCP.

This implementation makes use of `super let`, which is unstable and might not exist in the future in its current form. However, it is entirely reasonable to assume future Rust will always have _a_ way of expressing temporary lifetimes like this, since the (stable) `pin!()` macro needs this too. (This was also the motivation for merging rust-lang#139114.)

(This is a second version of rust-lang#139135)

Author: bors

tests/ui/author/macro_in_closure.stdout

@@ -9,28 +9,35 @@ if let StmtKind::Let(local) = stmt.kind
     && let ExprKind::Call(func, args) = e.kind
     && paths::STD_IO_STDIO__PRINT.matches_path(cx, func) // Add the path to `clippy_utils::paths` if needed
     && args.len() == 1
-    && let ExprKind::Call(func1, args1) = args[0].kind
-    && paths::CORE_FMT_RT_NEW_V1.matches_path(cx, func1) // Add the path to `clippy_utils::paths` if needed
-    && args1.len() == 2
+    && let ExprKind::Block(block1, None) = args[0].kind
+    && block1.stmts.len() == 1
+    && let StmtKind::Let(local1) = block1.stmts[0].kind
+    && let Some(init1) = local1.init
+    && let ExprKind::Array(elements) = init1.kind
+    && elements.len() == 1
+    && let ExprKind::Call(func1, args1) = elements[0].kind
+    && paths::CORE_FMT_RT_ARGUMENT_NEW_DISPLAY.matches_path(cx, func1) // Add the path to `clippy_utils::paths` if needed
+    && args1.len() == 1
     && let ExprKind::AddrOf(BorrowKind::Ref, Mutability::Not, inner) = args1[0].kind
-    && let ExprKind::Array(elements) = inner.kind
-    && elements.len() == 2
-    && let ExprKind::Lit(ref lit) = elements[0].kind
+    && let PatKind::Binding(BindingMode::NONE, _, name, None) = local1.pat.kind
+    && name.as_str() == "args"
+    && let Some(trailing_expr) = block1.expr
+    && let ExprKind::Call(func2, args2) = trailing_expr.kind
+    && paths::CORE_FMT_RT_NEW_V1.matches_path(cx, func2) // Add the path to `clippy_utils::paths` if needed
+    && args2.len() == 2
+    && let ExprKind::AddrOf(BorrowKind::Ref, Mutability::Not, inner1) = args2[0].kind
+    && let ExprKind::Array(elements1) = inner1.kind
+    && elements1.len() == 2
+    && let ExprKind::Lit(ref lit) = elements1[0].kind
     && let LitKind::Str(s, _) = lit.node
     && s.as_str() == ""
-    && let ExprKind::Lit(ref lit1) = elements[1].kind
+    && let ExprKind::Lit(ref lit1) = elements1[1].kind
     && let LitKind::Str(s1, _) = lit1.node
     && s1.as_str() == "\n"
-    && let ExprKind::AddrOf(BorrowKind::Ref, Mutability::Not, inner1) = args1[1].kind
-    && let ExprKind::Array(elements1) = inner1.kind
-    && elements1.len() == 1
-    && let ExprKind::Call(func2, args2) = elements1[0].kind
-    && paths::CORE_FMT_RT_ARGUMENT_NEW_DISPLAY.matches_path(cx, func2) // Add the path to `clippy_utils::paths` if needed
-    && args2.len() == 1
-    && let ExprKind::AddrOf(BorrowKind::Ref, Mutability::Not, inner2) = args2[0].kind
+    && let ExprKind::AddrOf(BorrowKind::Ref, Mutability::Not, inner2) = args2[1].kind
     && block.expr.is_none()
-    && let PatKind::Binding(BindingMode::NONE, _, name, None) = local.pat.kind
-    && name.as_str() == "print_text"
+    && let PatKind::Binding(BindingMode::NONE, _, name1, None) = local.pat.kind
+    && name1.as_str() == "print_text"
 {
     // report your lint here
 }

tests/ui/author/macro_in_loop.stdout

@@ -19,25 +19,32 @@ if let Some(higher::ForLoop { pat: pat, arg: arg, body: body, .. }) = higher::Fo
     && let ExprKind::Call(func, args) = e1.kind
     && paths::STD_IO_STDIO__PRINT.matches_path(cx, func) // Add the path to `clippy_utils::paths` if needed
     && args.len() == 1
-    && let ExprKind::Call(func1, args1) = args[0].kind
-    && paths::CORE_FMT_RT_NEW_V1.matches_path(cx, func1) // Add the path to `clippy_utils::paths` if needed
-    && args1.len() == 2
+    && let ExprKind::Block(block2, None) = args[0].kind
+    && block2.stmts.len() == 1
+    && let StmtKind::Let(local) = block2.stmts[0].kind
+    && let Some(init) = local.init
+    && let ExprKind::Array(elements) = init.kind
+    && elements.len() == 1
+    && let ExprKind::Call(func1, args1) = elements[0].kind
+    && paths::CORE_FMT_RT_ARGUMENT_NEW_DISPLAY.matches_path(cx, func1) // Add the path to `clippy_utils::paths` if needed
+    && args1.len() == 1
     && let ExprKind::AddrOf(BorrowKind::Ref, Mutability::Not, inner) = args1[0].kind
-    && let ExprKind::Array(elements) = inner.kind
-    && elements.len() == 2
-    && let ExprKind::Lit(ref lit2) = elements[0].kind
+    && let PatKind::Binding(BindingMode::NONE, _, name1, None) = local.pat.kind
+    && name1.as_str() == "args"
+    && let Some(trailing_expr) = block2.expr
+    && let ExprKind::Call(func2, args2) = trailing_expr.kind
+    && paths::CORE_FMT_RT_NEW_V1.matches_path(cx, func2) // Add the path to `clippy_utils::paths` if needed
+    && args2.len() == 2
+    && let ExprKind::AddrOf(BorrowKind::Ref, Mutability::Not, inner1) = args2[0].kind
+    && let ExprKind::Array(elements1) = inner1.kind
+    && elements1.len() == 2
+    && let ExprKind::Lit(ref lit2) = elements1[0].kind
     && let LitKind::Str(s, _) = lit2.node
     && s.as_str() == ""
-    && let ExprKind::Lit(ref lit3) = elements[1].kind
+    && let ExprKind::Lit(ref lit3) = elements1[1].kind
     && let LitKind::Str(s1, _) = lit3.node
     && s1.as_str() == "\n"
-    && let ExprKind::AddrOf(BorrowKind::Ref, Mutability::Not, inner1) = args1[1].kind
-    && let ExprKind::Array(elements1) = inner1.kind
-    && elements1.len() == 1
-    && let ExprKind::Call(func2, args2) = elements1[0].kind
-    && paths::CORE_FMT_RT_ARGUMENT_NEW_DISPLAY.matches_path(cx, func2) // Add the path to `clippy_utils::paths` if needed
-    && args2.len() == 1
-    && let ExprKind::AddrOf(BorrowKind::Ref, Mutability::Not, inner2) = args2[0].kind
+    && let ExprKind::AddrOf(BorrowKind::Ref, Mutability::Not, inner2) = args2[1].kind
     && block1.expr.is_none()
     && block.expr.is_none()
 {

tests/ui/manual_inspect.fixed

@@ -154,7 +154,6 @@ fn main() {
     });
 
     let _ = [0]
-        //~^ suspicious_map
         .into_iter()
         .inspect(|&x| {
             //~^ manual_inspect

tests/ui/manual_inspect.rs

@@ -165,7 +165,6 @@ fn main() {
     });
 
     let _ = [0]
-        //~^ suspicious_map
         .into_iter()
         .map(|x| {
             //~^ manual_inspect

tests/ui/manual_inspect.stderr

@@ -157,25 +157,8 @@ LL |
 LL ~         println!("{}", x);
    |
 
-error: this call to `map()` won't have an effect on the call to `count()`
-  --> tests/ui/manual_inspect.rs:167:13
-   |
-LL |       let _ = [0]
-   |  _____________^
-LL | |
-LL | |         .into_iter()
-LL | |         .map(|x| {
-...  |
-LL | |         })
-LL | |         .count();
-   | |________________^
-   |
-   = help: make sure you did not confuse `map` with `filter`, `for_each` or `inspect`
-   = note: `-D clippy::suspicious-map` implied by `-D warnings`
-   = help: to override `-D warnings` add `#[allow(clippy::suspicious_map)]`
-
 error: using `map` over `inspect`
-  --> tests/ui/manual_inspect.rs:170:10
+  --> tests/ui/manual_inspect.rs:169:10
    |
 LL |         .map(|x| {
    |          ^^^
@@ -188,7 +171,7 @@ LL ~             println!("{}", x);
    |
 
 error: using `map` over `inspect`
-  --> tests/ui/manual_inspect.rs:203:30
+  --> tests/ui/manual_inspect.rs:202:30
    |
 LL |     if let Some(x) = Some(1).map(|x| { println!("{x}");
    |                              ^^^
@@ -200,5 +183,5 @@ LL |         // Do not collapse code into this comment
 LL ~          }) {
    |
 
-error: aborting due to 14 previous errors
+error: aborting due to 13 previous errors