diff --git a/compiler-cli/src/add.rs b/compiler-cli/src/add.rs
index ac666b796..19a0d1550 100644
--- a/compiler-cli/src/add.rs
+++ b/compiler-cli/src/add.rs
@@ -2,6 +2,7 @@
 // SPDX-FileCopyrightText: 2021 The Gleam contributors
 
 use camino::{Utf8Path, Utf8PathBuf};
+use std::fmt::Write as _;
 
 use gleam_core::{
     Error, Result,
@@ -113,10 +114,12 @@ fn read_toml_edit(name: &Utf8Path) -> Result<toml_edit::DocumentMut, Error> {
 
 fn version_to_string(version: &Version) -> String {
     let mut text = String::new();
-    text.push_str(&format!(
+    let _ = write!(
+        text,
         "{}.{}.{}",
         version.major, version.minor, version.patch
-    ));
+    );
+
     if !version.pre.is_empty() {
         text.push('-');
         for (i, identifier) in version.pre.iter().enumerate() {
@@ -130,7 +133,7 @@ fn version_to_string(version: &Version) -> String {
         }
     }
     if let Some(build) = version.build.as_ref() {
-        text.push_str(&format!("+{build}"));
+        let _ = write!(text, "+{build}");
     }
     text
 }
diff --git a/compiler-cli/src/lib.rs b/compiler-cli/src/lib.rs
index b6df93792..afe45d638 100644
--- a/compiler-cli/src/lib.rs
+++ b/compiler-cli/src/lib.rs
@@ -24,6 +24,7 @@
     clippy::verbose_file_reads,
     clippy::unnested_or_patterns,
     clippy::default_trait_access,
+    clippy::format_push_string,
     rust_2018_idioms,
     missing_debug_implementations,
     missing_copy_implementations,
diff --git a/compiler-core/src/derivation_tree.rs b/compiler-core/src/derivation_tree.rs
index 0034c16b5..381e4eaba 100644
--- a/compiler-core/src/derivation_tree.rs
+++ b/compiler-core/src/derivation_tree.rs
@@ -13,6 +13,7 @@ use petgraph::prelude::StableGraph;
 use pubgrub::External;
 use pubgrub::{DerivationTree, Derived, Ranges};
 use std::collections::HashMap;
+use std::fmt::Write as _;
 use std::hash::RandomState;
 use std::ops::Bound::{Excluded, Included, Unbounded};
 use std::sync::Arc;
@@ -171,10 +172,11 @@ impl DerivationTreePrinter {
                 .ranges_between(previous, next)
                 .expect("path edge is in the graph");
 
-            message.push_str(&format!(
+            let _ = write!(
+                message,
                 "\n    - {previous_name} requires {next_name} {}",
                 pretty_range(next_range)
-            ));
+            );
             previous = next;
         }
         message
diff --git a/compiler-core/src/docs/tests.rs b/compiler-core/src/docs/tests.rs
index 5c9bcf5cb..b2d8440a7 100644
--- a/compiler-core/src/docs/tests.rs
+++ b/compiler-core/src/docs/tests.rs
@@ -3,6 +3,7 @@
 
 use std::{
     collections::{HashMap, HashSet},
+    fmt::Write as _,
     time::SystemTime,
 };
 
@@ -200,7 +201,7 @@ fn compile_documentation(
 
     output.push_str("---- SOURCE CODE\n");
     for (_package, name, src) in modules {
-        output.push_str(&format!("-- {name}.gleam\n{src}\n\n"));
+        let _ = write!(output, "-- {name}.gleam\n{src}\n\n");
     }
     output.push_str("-- ");
     output.push_str(module_name);
diff --git a/compiler-core/src/error.rs b/compiler-core/src/error.rs
index c1229c916..75760af4b 100644
--- a/compiler-core/src/error.rs
+++ b/compiler-core/src/error.rs
@@ -7,6 +7,7 @@ use crate::bit_array::UnsupportedOption;
 use crate::build::{Origin, Outcome, Runtime, Target};
 use crate::dependency::{PackageFetcher, ResolutionError};
 use crate::diagnostic::{Diagnostic, ExtraLabel, Label, Location};
+use std::fmt::Write as _;
 
 use crate::derivation_tree::DerivationTreePrinter;
 use crate::parse::error::ParseErrorDetails;
@@ -3535,7 +3536,7 @@ but no type in scope with that name."
                         };
                         text.push_str(message);
                         for module_name in possible_modules {
-                            text.push_str(&format!("  - {module_name}.{name}\n"))
+                            let _ = writeln!(text, "  - {module_name}.{name}");
                         }
                     }
 
@@ -4648,10 +4649,11 @@ here takes {expected_string}.\n"
 the `use` callback function.\n",
                     )
                 } else {
-                    text.push_str(&format!(
+                    let _ = writeln!(
+                        text,
                         "You supplied {supplied_arguments_string} \
-and the final one is the `use` callback function.\n"
-                    ));
+and the final one is the `use` callback function."
+                    );
                 }
             } else {
                 text.push_str(
diff --git a/compiler-core/src/javascript/tests.rs b/compiler-core/src/javascript/tests.rs
index b5c06bdc6..f1d5214d6 100644
--- a/compiler-core/src/javascript/tests.rs
+++ b/compiler-core/src/javascript/tests.rs
@@ -47,13 +47,14 @@ pub static CURRENT_PACKAGE: &str = "thepackage";
 #[macro_export]
 macro_rules! assert_js {
     ($(($name:literal, $module_src:literal)),+, $src:literal $(,)?) => {
+        use std::fmt::Write as _;
         let compiled =
             $crate::javascript::tests::compile_js($src, vec![$(($crate::javascript::tests::CURRENT_PACKAGE, $name, $module_src)),*]);
             let mut output = String::from("----- SOURCE CODE\n");
             for (name, src) in [$(($name, $module_src)),*] {
-                output.push_str(&format!("-- {name}.gleam\n{src}\n\n"));
+                let _ = write!(output, "-- {name}.gleam\n{src}\n\n");
             }
-            output.push_str(&format!("-- main.gleam\n{}\n\n----- COMPILED JAVASCRIPT\n{compiled}", $src));
+            let _ = write!(output, "-- main.gleam\n{}\n\n----- COMPILED JAVASCRIPT\n{compiled}", $src);
         insta::assert_snapshot!(insta::internals::AutoName, output, $src);
     };
 
@@ -332,13 +333,11 @@ pub fn source_map_to_string(src: &str, compiled: &str, source_map: SourceMap) ->
             src_line_numbers.byte_index(Position::new(*next_src_line, *next_src_col)) as usize;
         let next_compiled_index =
             compiled_line_numbers.byte_index(Position::new(*next_dst_line, *next_dst_col)) as usize;
-        output.push_str(&format!("{}\n", &src[src_index..next_src_index]));
-        output.push_str("⏷\n");
-        output.push_str(&format!(
-            "{}\n",
-            &compiled[compiled_index..next_compiled_index]
-        ));
-        output.push_str("----- \n");
+
+        output.push_str(&src[src_index..next_src_index]);
+        output.push_str("\n⏷\n");
+        output.push_str(&compiled[compiled_index..next_compiled_index]);
+        output.push_str("\n----- \n");
         prev_compiled_index = next_compiled_index;
     }
     // Print the last mapping. this needs to be done separately because the last mapping
@@ -353,15 +352,17 @@ pub fn source_map_to_string(src: &str, compiled: &str, source_map: SourceMap) ->
             let next_src_index = src_line_numbers
                 .byte_index(Position::new(next_src_token.0, next_src_token.1))
                 as usize;
-            output.push_str(&format!("{}\n", &src[src_index..next_src_index]));
+            output.push_str(&src[src_index..next_src_index]);
+            output.push('\n');
         }
         None => {
             // If there is no next src token, print the rest of the source and compiled code
-            output.push_str(&format!("{}\n", &src[src_index..]));
+            output.push_str(&src[src_index..]);
+            output.push('\n');
         }
     }
     output.push_str("⏷\n");
-    output.push_str(&format!("{}\n", &compiled[prev_compiled_index..]));
-    output.push_str("----- \n");
+    output.push_str(&compiled[prev_compiled_index..]);
+    output.push_str("\n----- \n");
     output
 }
diff --git a/compiler-core/src/lib.rs b/compiler-core/src/lib.rs
index c1cd22c3c..50769b388 100644
--- a/compiler-core/src/lib.rs
+++ b/compiler-core/src/lib.rs
@@ -25,6 +25,7 @@
     clippy::verbose_file_reads,
     clippy::unnested_or_patterns,
     clippy::default_trait_access,
+    clippy::format_push_string,
     rust_2018_idioms,
     missing_debug_implementations,
     missing_copy_implementations,
diff --git a/compiler-core/src/type_/tests.rs b/compiler-core/src/type_/tests.rs
index d21c685b7..13ad6ca70 100644
--- a/compiler-core/src/type_/tests.rs
+++ b/compiler-core/src/type_/tests.rs
@@ -90,6 +90,8 @@ macro_rules! assert_module_error {
     };
 
     ($(($name:expr, $module_src:literal)),+, $src:literal $(,)?) => {
+        use std::fmt::Write as _;
+
         let error = $crate::type_::tests::module_error(
             $src,
             vec![
@@ -99,13 +101,15 @@ macro_rules! assert_module_error {
 
         let mut output = String::from("----- SOURCE CODE\n");
         for (name, src) in [$(($name, $module_src)),*] {
-            output.push_str(&format!("-- {name}.gleam\n{src}\n\n"));
+            let _ = write!(output, "-- {name}.gleam\n{src}\n\n");
         }
-        output.push_str(&format!("-- main.gleam\n{}\n\n----- ERROR\n{error}", $src));
+        let _ = write!(output, "-- main.gleam\n{}\n\n----- ERROR\n{error}", $src);
         insta::assert_snapshot!(insta::internals::AutoName, output, $src);
     };
 
     ($(($package:literal, $name:expr, $module_src:literal)),+, $src:literal $(,)?) => {
+        use std::fmt::Write as _;
+
         let error = $crate::type_::tests::module_error(
             $src,
             vec![
@@ -115,9 +119,9 @@ macro_rules! assert_module_error {
 
         let mut output = String::from("----- SOURCE CODE\n");
         for (name, src) in [$(($name, $module_src)),*] {
-            output.push_str(&format!("-- {name}.gleam\n{src}\n\n"));
+            let _ = write!(output, "-- {name}.gleam\n{src}\n\n");
         }
-        output.push_str(&format!("-- main.gleam\n{}\n\n----- ERROR\n{error}", $src));
+        let _ = write!(output, "-- main.gleam\n{}\n\n----- ERROR\n{error}", $src);
         insta::assert_snapshot!(insta::internals::AutoName, output, $src);
     };
 }
@@ -231,6 +235,8 @@ macro_rules! assert_warning {
     };
 
     ($(($name:expr, $module_src:literal)),+, $src:literal $(,)?) => {
+        use std::fmt::Write as _;
+
         let warning = $crate::type_::tests::get_printed_warnings(
             $src,
             vec![
@@ -243,13 +249,15 @@ macro_rules! assert_warning {
 
         let mut output = String::from("----- SOURCE CODE\n");
         for (name, src) in [$(($name, $module_src)),*] {
-            output.push_str(&format!("-- {name}.gleam\n{src}\n\n"));
+            let _ = write!(output, "-- {name}.gleam\n{src}\n\n");
         }
-        output.push_str(&format!("-- main.gleam\n{}\n\n----- WARNING\n{warning}", $src));
+        let _ = write!(output, "-- main.gleam\n{}\n\n----- WARNING\n{warning}", $src);
         insta::assert_snapshot!(insta::internals::AutoName, output, $src);
     };
 
     ($(($package:expr, $name:expr, $module_src:literal)),+, $src:expr) => {
+        use std::fmt::Write as _;
+
         let warning = $crate::type_::tests::get_printed_warnings(
             $src,
             vec![$(($package, $name, $module_src)),*],
@@ -260,9 +268,9 @@ macro_rules! assert_warning {
 
         let mut output = String::from("----- SOURCE CODE\n");
         for (name, src) in [$(($name, $module_src)),*] {
-            output.push_str(&format!("-- {name}.gleam\n{src}\n\n"));
+            let _ = write!(output, "-- {name}.gleam\n{src}\n\n");
         }
-        output.push_str(&format!("-- main.gleam\n{}\n\n----- WARNING\n{warning}", $src));
+        let _ = write!(output, "-- main.gleam\n{}\n\n----- WARNING\n{warning}", $src);
         insta::assert_snapshot!(insta::internals::AutoName, output, $src);
     };
 }
diff --git a/compiler-core/src/warning.rs b/compiler-core/src/warning.rs
index a350f94d2..d01bbcdfe 100644
--- a/compiler-core/src/warning.rs
+++ b/compiler-core/src/warning.rs
@@ -22,6 +22,7 @@ use debug_ignore::DebugIgnore;
 use ecow::EcoString;
 use itertools::Itertools;
 use std::{
+    fmt::Write as _,
     io::Write,
     sync::{Arc, atomic::Ordering},
 };
@@ -1100,9 +1101,12 @@ Either change the pattern or use `panic` to unconditionally fail.",
                     };
                     let mut text = format!("`{name}` is not a function");
                     match arguments {
-                        0 => text.push_str(&format!(
-                            ", you can just write `{name}` instead of `{name}()`."
-                        )),
+                        0 => {
+                            let _ = write!(
+                                text,
+                                ", you can just write `{name}` instead of `{name}()`."
+                            );
+                        }
                         1 => text.push_str(
                             " and will crash before it can do anything with this argument.",
                         ),
diff --git a/language-server/src/lib.rs b/language-server/src/lib.rs
index 065983fec..feba8ef71 100644
--- a/language-server/src/lib.rs
+++ b/language-server/src/lib.rs
@@ -23,6 +23,7 @@
     clippy::verbose_file_reads,
     clippy::unnested_or_patterns,
     clippy::default_trait_access,
+    clippy::format_push_string,
     rust_2018_idioms,
     missing_debug_implementations,
     missing_copy_implementations,
diff --git a/language-server/src/tests/action.rs b/language-server/src/tests/action.rs
index 147dcf49e..4527122c4 100644
--- a/language-server/src/tests/action.rs
+++ b/language-server/src/tests/action.rs
@@ -6,6 +6,7 @@ use lsp_types::{
     CodeActionContext, CodeActionParams, DocumentChange, PartialResultParams, Position, Uri as Url,
     WorkDoneProgressParams,
 };
+use std::fmt::Write as _;
 
 use super::*;
 use crate::path;
@@ -248,7 +249,7 @@ macro_rules! assert_code_action {
         );
 
         if !file_operations.is_empty() {
-            output.push_str(&format!("\n----- FILE OPERATIONS -----\n{file_operations}"));
+            let _ = write!(output, "\n----- FILE OPERATIONS -----\n{file_operations}");
         }
 
         insta::assert_snapshot!(insta::internals::AutoName, output, src);
diff --git a/language-server/src/tests/document_highlight.rs b/language-server/src/tests/document_highlight.rs
index 47c0a571c..3d5590438 100644
--- a/language-server/src/tests/document_highlight.rs
+++ b/language-server/src/tests/document_highlight.rs
@@ -86,6 +86,8 @@ macro_rules! assert_highlights {
     };
 
     ($project:expr, $position:expr $(,)?) => {
+        use std::fmt::Write as _;
+
         let project = $project;
         let src = project.src;
         let position = $position.find_position(src);
@@ -99,20 +101,22 @@ macro_rules! assert_highlights {
             } else {
                 &Vec::new()
             };
-            output.push_str(&format!(
+            let _ = write!(
+                output,
                 "-- {name}.gleam\n{}\n\n",
                 show_highlights(src, None, highlights_in_module)
-            ));
+            );
         }
         let highlights_in_app_module = if module_name == "app" {
             &result
         } else {
             &Vec::new()
         };
-        output.push_str(&format!(
+        let _ = write!(
+            output,
             "-- app.gleam\n{}",
             show_highlights(src, Some(position), highlights_in_app_module)
-        ));
+        );
 
         insta::assert_snapshot!(insta::internals::AutoName, output, src);
     };
diff --git a/language-server/src/tests/reference.rs b/language-server/src/tests/reference.rs
index 19d743f01..3cac0cfb7 100644
--- a/language-server/src/tests/reference.rs
+++ b/language-server/src/tests/reference.rs
@@ -94,6 +94,8 @@ macro_rules! assert_references {
     };
 
     ($project:expr, $position:expr $(,)?) => {
+        use std::fmt::Write as _;
+
         let project = $project;
         let src = project.src;
         let position = $position.find_position(src);
@@ -101,19 +103,21 @@ macro_rules! assert_references {
 
         let mut output = String::new();
         for (name, src) in project.root_package_modules.iter() {
-            output.push_str(&format!(
+            let _ = write!(
+                output,
                 "-- {name}.gleam\n{}\n\n",
                 show_references(src, None, result.get(*name).unwrap_or(&Vec::new()))
-            ));
+            );
         }
-        output.push_str(&format!(
+        let _ = write!(
+            output,
             "-- app.gleam\n{}",
             show_references(
                 src,
                 Some(position),
                 result.get("app").unwrap_or(&Vec::new())
             )
-        ));
+        );
 
         insta::assert_snapshot!(insta::internals::AutoName, output, src);
     };
diff --git a/language-server/src/tests/rename.rs b/language-server/src/tests/rename.rs
index 1689e64a2..853beaf29 100644
--- a/language-server/src/tests/rename.rs
+++ b/language-server/src/tests/rename.rs
@@ -2,6 +2,7 @@
 // SPDX-FileCopyrightText: 2025 The Gleam contributors
 
 use std::collections::HashMap;
+use std::fmt::Write as _;
 
 use lsp_types::{
     Position, PrepareRenameParams, PrepareRenamePlaceholder, Range, RenameParams,
@@ -119,7 +120,7 @@ fn display_result(
 ) -> String {
     let mut output = String::from("----- BEFORE RENAME\n");
     for (name, src) in project.root_package_modules.iter() {
-        output.push_str(&format!("-- {name}.gleam\n{src}\n\n"));
+        let _ = write!(output, "-- {name}.gleam\n{src}\n\n");
     }
 
     let src = project.src;
@@ -128,9 +129,10 @@ fn display_result(
     } else {
         src.to_string()
     };
-    output.push_str(&format!(
+    let _ = write!(
+        output,
         "-- app.gleam\n{app_src_before}\n\n----- AFTER RENAME\n",
-    ));
+    );
 
     for &(name, src) in project.root_package_modules.iter() {
         let used_name = if let Some(new_name) = renamed_modules.get(name) {
@@ -138,21 +140,23 @@ fn display_result(
         } else {
             name
         };
-        output.push_str(&format!(
+        let _ = write!(
+            output,
             "-- {used_name}.gleam\n{}\n\n",
             modules
                 .get(name)
                 .map(|string| string.as_str())
                 .unwrap_or(src)
-        ));
+        );
     }
-    output.push_str(&format!(
+    let _ = write!(
+        output,
         "-- app.gleam\n{}",
         modules
             .get("app")
             .map(|string| string.as_str())
             .unwrap_or(src)
-    ));
+    );
     output
 }
 
diff --git a/test-package-compiler/build.rs b/test-package-compiler/build.rs
index f8b438ebf..633f50e46 100644
--- a/test-package-compiler/build.rs
+++ b/test-package-compiler/build.rs
@@ -1,6 +1,7 @@
 // SPDX-License-Identifier: Apache-2.0
 // SPDX-FileCopyrightText: 2022 The Gleam contributors
 
+use std::fmt::Write as _;
 use std::path::PathBuf;
 
 pub fn main() {
@@ -25,7 +26,8 @@ pub fn main() {
     for name in names {
         let path = cases.join(&name);
         let path = path.to_str().unwrap().replace('\\', "/");
-        module.push_str(&format!(
+        let _ = write!(
+            module,
             r#"
 #[rustfmt::skip]
 #[test]
@@ -38,7 +40,7 @@ fn {name}() {{
     );
 }}
 "#
-        ));
+        );
     }
 
     let out = PathBuf::from("./src/generated_tests.rs");