diff --git a/Cargo.toml b/Cargo.toml
index 8321ceb..068992b 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -41,3 +41,7 @@ nightly = []
 
 [lints.rust]
 unexpected_cfgs = { level = "warn", check-cfg = ['cfg(run_ui_tests)'] }
+
+[lints.clippy]
+pedantic = { level = "warn", priority = -1 }
+module_name_repetitions = { level = "allow" }
diff --git a/proc-macro-error-attr/Cargo.toml b/proc-macro-error-attr/Cargo.toml
index 5041bb3..67098fd 100644
--- a/proc-macro-error-attr/Cargo.toml
+++ b/proc-macro-error-attr/Cargo.toml
@@ -20,3 +20,6 @@ targets = ["x86_64-unknown-linux-gnu"]
 [dependencies]
 quote = "1"
 proc-macro2 = "1"
+
+[lints.clippy]
+pedantic = { level = "warn", priority = -1 }
diff --git a/proc-macro-error-attr/src/lib.rs b/proc-macro-error-attr/src/lib.rs
index 2ae9003..6b711c0 100644
--- a/proc-macro-error-attr/src/lib.rs
+++ b/proc-macro-error-attr/src/lib.rs
@@ -7,7 +7,11 @@ use proc_macro::TokenStream;
 use proc_macro2::{Literal, Span, TokenStream as TokenStream2, TokenTree};
 use quote::{quote, quote_spanned};
 
-use crate::settings::{Setting::*, *};
+use crate::settings::{
+    parse_settings,
+    Setting::{AllowNotMacro, AssertUnwindSafe, ProcMacroHack},
+    Settings,
+};
 
 mod parse;
 mod settings;
@@ -71,7 +75,7 @@ fn impl_proc_macro_error(attr: TokenStream2, input: TokenStream2) -> Result<Toke
         ));
     }
 
-    let body = gen_body(body, settings);
+    let body = gen_body(&body, &settings);
 
     let res = quote! {
         #(#attrs)*
@@ -81,7 +85,7 @@ fn impl_proc_macro_error(attr: TokenStream2, input: TokenStream2) -> Result<Toke
     Ok(res.into())
 }
 
-fn gen_body(block: TokenTree, settings: Settings) -> proc_macro2::TokenStream {
+fn gen_body(block: &TokenTree, settings: &Settings) -> proc_macro2::TokenStream {
     let is_proc_macro_hack = settings.is_set(ProcMacroHack);
     let closure = if settings.is_set(AssertUnwindSafe) {
         quote!(::std::panic::AssertUnwindSafe(|| #block ))
diff --git a/proc-macro-error-attr/src/parse.rs b/proc-macro-error-attr/src/parse.rs
index 6f4663f..eedb495 100644
--- a/proc-macro-error-attr/src/parse.rs
+++ b/proc-macro-error-attr/src/parse.rs
@@ -39,7 +39,7 @@ fn parse_next_attr(
             res
         }
         other => {
-            let span = other.map_or(Span::call_site(), |tt| tt.span());
+            let span = other.map_or(Span::call_site(), TokenTree::span);
             return Err(Error::new(span, "expected `[`".to_string()));
         }
     };
diff --git a/proc-macro-error-attr/src/settings.rs b/proc-macro-error-attr/src/settings.rs
index 0b7ec76..f87bd0b 100644
--- a/proc-macro-error-attr/src/settings.rs
+++ b/proc-macro-error-attr/src/settings.rs
@@ -3,7 +3,7 @@ use proc_macro2::{Ident, Span, TokenStream, TokenTree};
 
 macro_rules! decl_settings {
     ($($val:expr => $variant:ident),+ $(,)*) => {
-        #[derive(PartialEq)]
+        #[derive(PartialEq, Clone, Copy)]
         pub(crate) enum Setting {
             $($variant),*
         }
@@ -67,6 +67,6 @@ impl Settings {
     }
 
     pub(crate) fn set(&mut self, setting: Setting) {
-        self.0.push(setting)
+        self.0.push(setting);
     }
 }
diff --git a/src/diagnostic.rs b/src/diagnostic.rs
index c818713..0455511 100644
--- a/src/diagnostic.rs
+++ b/src/diagnostic.rs
@@ -18,6 +18,7 @@ pub enum Level {
 
 /// Represents a single diagnostic message
 #[derive(Debug)]
+#[must_use = "A diagnostic does nothing unless emitted"]
 pub struct Diagnostic {
     pub(crate) level: Level,
     pub(crate) span_range: SpanRange,
@@ -42,6 +43,7 @@ pub trait DiagnosticExt: Sealed {
     ///
     /// This function is the same as `Diagnostic::span_error` but produces considerably
     /// better error messages for multi-token spans on stable.
+    #[must_use]
     fn span_range_error(self, span_range: SpanRange, msg: String) -> Self;
 
     /// Attach a "help" note to your main message, the note will have it's own span on nightly.
@@ -52,6 +54,7 @@ pub trait DiagnosticExt: Sealed {
     /// # Span
     ///
     /// The span is ignored on stable, the note effectively inherits its parent's (main message) span
+    #[must_use]
     fn span_range_help(self, span_range: SpanRange, msg: String) -> Self;
 
     /// Attach a note to your main message, the note will have it's own span on nightly.
@@ -62,6 +65,7 @@ pub trait DiagnosticExt: Sealed {
     /// # Span
     ///
     /// The span is ignored on stable, the note effectively inherits its parent's (main message) span
+    #[must_use]
     fn span_range_note(self, span_range: SpanRange, msg: String) -> Self;
 }
 
@@ -167,6 +171,7 @@ impl Diagnostic {
     }
 
     /// The message of main warning/error (no notes attached)
+    #[must_use]
     pub fn message(&self) -> &str {
         &self.msg
     }
diff --git a/src/dummy.rs b/src/dummy.rs
index 0da03be..5bc98bd 100644
--- a/src/dummy.rs
+++ b/src/dummy.rs
@@ -126,6 +126,7 @@ thread_local! {
 /// invocations in case you'll emit any errors.
 ///
 /// See [guide](../index.html#guide).
+#[allow(clippy::must_use_candidate)] // Mutates thread local state
 pub fn set_dummy(dummy: TokenStream) -> Option<TokenStream> {
     check_correctness();
     DUMMY_IMPL.with(|old_dummy| old_dummy.replace(Some(dummy)))
diff --git a/src/lib.rs b/src/lib.rs
index 5fc0dbf..ebc9835 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -273,7 +273,6 @@
 
 #![cfg_attr(feature = "nightly", feature(proc_macro_diagnostic))]
 #![forbid(unsafe_code)]
-#![allow(clippy::needless_doctest_main)]
 
 extern crate proc_macro;
 
@@ -304,6 +303,7 @@ mod imp;
 mod imp;
 
 #[derive(Debug, Clone, Copy)]
+#[must_use = "A SpanRange does nothing unless used"]
 pub struct SpanRange {
     pub first: Span,
     pub last: Span,
@@ -349,6 +349,7 @@ impl SpanRange {
     }
 
     /// Collapse the range into single span, preserving as much information as possible.
+    #[must_use]
     pub fn collapse(self) -> Span {
         self.first.join(self.last).unwrap_or(self.first)
     }
@@ -479,12 +480,11 @@ thread_local! {
 struct AbortNow;
 
 fn check_correctness() {
-    if ENTERED_ENTRY_POINT.with(|flag| flag.get()) == 0 {
-        panic!(
-            "proc-macro-error API cannot be used outside of `entry_point` invocation, \
+    assert!(
+        ENTERED_ENTRY_POINT.with(Cell::get) != 0,
+        "proc-macro-error API cannot be used outside of `entry_point` invocation, \
              perhaps you forgot to annotate your #[proc_macro] function with `#[proc_macro_error]"
-        );
-    }
+    );
 }
 
 /// **ALL THE STUFF INSIDE IS NOT PUBLIC API!!!**
@@ -525,11 +525,16 @@ pub mod __export {
     impl<T: ToTokens> ToTokensAsSpanRange for &T {
         fn FIRST_ARG_MUST_EITHER_BE_Span_OR_IMPLEMENT_ToTokens_OR_BE_SpanRange(&self) -> SpanRange {
             let mut ts = self.to_token_stream().into_iter();
-            let first = ts
-                .next()
-                .map(|tt| tt.span())
-                .unwrap_or_else(Span::call_site);
-            let last = ts.last().map(|tt| tt.span()).unwrap_or(first);
+            let first = match ts.next() {
+                Some(t) => t.span(),
+                None => Span::call_site(),
+            };
+
+            let last = match ts.next() {
+                Some(t) => t.span(),
+                None => first,
+            };
+
             SpanRange { first, last }
         }
     }
diff --git a/test-crate/Cargo.toml b/test-crate/Cargo.toml
index 146bfd4..254cb09 100644
--- a/test-crate/Cargo.toml
+++ b/test-crate/Cargo.toml
@@ -20,3 +20,7 @@ proc-macro2 = "1"
 [dependencies.syn]
 version = "2"
 features = ["full"]
+
+[lints.clippy]
+pedantic = { level = "warn", priority = -1 }
+module_name_repetitions = { level = "allow" }
diff --git a/test-crate/lib.rs b/test-crate/lib.rs
index d50b983..1ecdfbc 100644
--- a/test-crate/lib.rs
+++ b/test-crate/lib.rs
@@ -143,7 +143,7 @@ pub fn emit_notes(input: proc_macro::TokenStream) -> proc_macro::TokenStream {
 #[proc_macro]
 #[proc_macro_error]
 pub fn option_ext(_input: proc_macro::TokenStream) -> proc_macro::TokenStream {
-    let none: Option<Diagnostic> = None;
+    let none: Option<()> = None;
     none.expect_or_abort("Option::expect_or_abort() test");
     quote!().into()
 }