Move format_push_string and format_collect to pedantic (#13894)

Closes #11434 by moving `format_push_string` and `format_collect` to
pedantic.

changelog: Move `format_push_string` and `format_collect` to pedantic

clippy_dev/src/new_lint.rs

@@ -255,8 +255,9 @@ fn get_lint_file_contents(lint: &LintData<'_>, enable_msrv: bool) -> String {
     let name_camel = to_camel_case(lint.name);
     let name_upper = lint_name.to_uppercase();
 
-    result.push_str(&if enable_msrv {
-        formatdoc!(
+    if enable_msrv {
+        let _: fmt::Result = writedoc!(
+            result,
             r"
             use clippy_utils::msrvs::{{self, Msrv}};
             use clippy_config::Conf;
@@ -265,22 +266,24 @@ fn get_lint_file_contents(lint: &LintData<'_>, enable_msrv: bool) -> String {
             use rustc_session::impl_lint_pass;
 
         "
-        )
+        );
     } else {
-        formatdoc!(
+        let _: fmt::Result = writedoc!(
+            result,
             r"
             {pass_import}
             use rustc_lint::{{{context_import}, {pass_type}}};
             use rustc_session::declare_lint_pass;
 
         "
-        )
-    });
+        );
+    }
 
     let _: fmt::Result = writeln!(result, "{}", get_lint_declaration(&name_upper, category));
 
-    result.push_str(&if enable_msrv {
-        formatdoc!(
+    if enable_msrv {
+        let _: fmt::Result = writedoc!(
+            result,
             r"
             pub struct {name_camel} {{
                 msrv: Msrv,
@@ -301,16 +304,17 @@ fn get_lint_file_contents(lint: &LintData<'_>, enable_msrv: bool) -> String {
             // TODO: Add MSRV level to `clippy_config/src/msrvs.rs` if needed.
             // TODO: Update msrv config comment in `clippy_config/src/conf.rs`
         "
-        )
+        );
     } else {
-        formatdoc!(
+        let _: fmt::Result = writedoc!(
+            result,
             r"
             declare_lint_pass!({name_camel} => [{name_upper}]);
 
             impl {pass_type}{pass_lifetimes} for {name_camel} {{}}
         "
-        )
-    });
+        );
+    }
 
     result
 }

clippy_lints/src/endian_bytes.rs

@@ -7,6 +7,7 @@ use rustc_middle::lint::in_external_macro;
 use rustc_middle::ty::Ty;
 use rustc_session::declare_lint_pass;
 use rustc_span::Symbol;
+use std::fmt::Write;
 
 declare_clippy_lint! {
     /// ### What it does
@@ -184,7 +185,7 @@ fn maybe_lint_endian_bytes(cx: &LateContext<'_>, expr: &Expr<'_>, prefix: Prefix
                     help_str.push_str("either of ");
                 }
 
-                help_str.push_str(&format!("`{ty}::{}` ", lint.as_name(prefix)));
+                write!(help_str, "`{ty}::{}` ", lint.as_name(prefix)).unwrap();
 
                 if i != len && !only_one {
                     help_str.push_str("or ");

clippy_lints/src/format_push_string.rs

@@ -11,7 +11,7 @@ declare_clippy_lint! {
     /// Detects cases where the result of a `format!` call is
     /// appended to an existing `String`.
     ///
-    /// ### Why restrict this?
+    /// ### Why is this bad?
     /// Introduces an extra, avoidable heap allocation.
     ///
     /// ### Known problems
@@ -35,7 +35,7 @@ declare_clippy_lint! {
     /// ```
     #[clippy::version = "1.62.0"]
     pub FORMAT_PUSH_STRING,
-    restriction,
+    pedantic,
     "`format!(..)` appended to existing `String`"
 }
 declare_lint_pass!(FormatPushString => [FORMAT_PUSH_STRING]);

clippy_lints/src/methods/mod.rs

@@ -3518,7 +3518,7 @@ declare_clippy_lint! {
     /// ```
     #[clippy::version = "1.73.0"]
     pub FORMAT_COLLECT,
-    perf,
+    pedantic,
     "`format!`ing every element in a collection, then collecting the strings into a new `String`"
 }