Add failing uninlined-format-args tests

All these tests are currently failing (generating uncompilable code).

* Implement a simplified `indoc!` proc macro
* added a `pass_through!(...)` macro test

The .fixed and .stderr were hacked without the `cargo dev bless`, so might be incorrect.

Author: nyurik

tests/ui/auxiliary/proc_macro_indoc.rs

@@ -0,0 +1,26 @@
+// compile-flags: --emit=link
+// no-prefer-dynamic
+
+#![crate_type = "proc-macro"]
+
+extern crate proc_macro;
+
+use proc_macro::{TokenStream, TokenTree};
+use std::str::FromStr;
+
+/// This code was adapted from the indoc crate
+#[proc_macro]
+pub fn simple_indoc(input: TokenStream) -> TokenStream {
+    let token = input.into_iter().next().unwrap();
+    let new_token = TokenStream::from_str(&token.to_string())
+        .unwrap()
+        .into_iter()
+        .next()
+        .unwrap();
+
+    if let TokenTree::Literal(mut lit) = new_token {
+        lit.set_span(token.span());
+        return TokenStream::from(TokenTree::Literal(lit));
+    }
+    panic!();
+}

tests/ui/uninlined_format_args.fixed

@@ -1,4 +1,5 @@
 // run-rustfix
+// aux-build:proc_macro_indoc.rs
 
 #![feature(custom_inner_attributes)]
 #![warn(clippy::uninlined_format_args)]
@@ -10,6 +11,8 @@
     clippy::print_literal
 )]
 
+extern crate proc_macro_indoc;
+
 macro_rules! no_param_str {
     () => {
         "{}"
@@ -150,11 +153,10 @@ fn tester(fn_arg: i32) {
     );
     println!(no_param_str!(), local_i32);
 
-    // FIXME: bugs!
-    // println!(pass_through!("foo={local_i32}"), local_i32 = local_i32);
-    // println!(pass_through!("foo={}"), local_i32);
-    // println!(indoc!("foo={}"), local_i32);
-    // printdoc!("foo={}", local_i32);
+    println!(pass_through!("foo={}"), local_i32);
+    println!(pass_through!("foo={a}"), a = local_i32);
+    println!(proc_macro_indoc::simple_indoc!("foo={}"), local_i32);
+    println!(proc_macro_indoc::simple_indoc!("foo={a}"), a = local_i32);
 }
 
 fn main() {

tests/ui/uninlined_format_args.rs

@@ -1,4 +1,5 @@
 // run-rustfix
+// aux-build:proc_macro_indoc.rs
 
 #![feature(custom_inner_attributes)]
 #![warn(clippy::uninlined_format_args)]
@@ -10,6 +11,8 @@
     clippy::print_literal
 )]
 
+extern crate proc_macro_indoc;
+
 macro_rules! no_param_str {
     () => {
         "{}"
@@ -153,11 +156,10 @@ fn tester(fn_arg: i32) {
     );
     println!(no_param_str!(), local_i32);
 
-    // FIXME: bugs!
-    // println!(pass_through!("foo={local_i32}"), local_i32 = local_i32);
-    // println!(pass_through!("foo={}"), local_i32);
-    // println!(indoc!("foo={}"), local_i32);
-    // printdoc!("foo={}", local_i32);
+    println!(pass_through!("foo={}"), local_i32);
+    println!(pass_through!("foo={a}"), a = local_i32);
+    println!(proc_macro_indoc::simple_indoc!("foo={}"), local_i32);
+    println!(proc_macro_indoc::simple_indoc!("foo={a}"), a = local_i32);
 }
 
 fn main() {