Don't apply string_lit_as_bytes if in macro expansion

clippy_lints/src/strings.rs

@@ -292,6 +292,7 @@ impl<'tcx> LateLintPass<'tcx> for StringLitAsBytes {
         }
 
         if_chain! {
+            if !in_external_macro(cx.sess(), e.span);
             if let ExprKind::MethodCall(path, receiver, ..) = &e.kind;
             if path.ident.name == sym!(as_bytes);
             if let ExprKind::Lit(lit) = &receiver.kind;

tests/ui/auxiliary/macro_rules.rs

@@ -21,6 +21,13 @@ macro_rules! string_add {
     };
 }
 
+#[macro_export]
+macro_rules! string_lit_as_bytes {
+    ($s:literal) => {
+        const C: &[u8] = $s.as_bytes();
+    };
+}
+
 #[macro_export]
 macro_rules! mut_mut {
     () => {

tests/ui/string_lit_as_bytes.fixed

@@ -1,8 +1,18 @@
 //@run-rustfix
+//@aux-build:macro_rules.rs
 
 #![allow(dead_code, unused_variables)]
 #![warn(clippy::string_lit_as_bytes)]
 
+#[macro_use]
+extern crate macro_rules;
+
+macro_rules! b {
+    ($b:literal) => {
+        const B: &[u8] = b"warning";
+    };
+}
+
 fn str_lit_as_bytes() {
     let bs = b"hello there";
 
@@ -11,6 +21,10 @@ fn str_lit_as_bytes() {
     let bs = b"lit to string".to_vec();
     let bs = b"lit to owned".to_vec();
 
+    b!("warning");
+
+    string_lit_as_bytes!("no warning");
+
     // no warning, because these cannot be written as byte string literals:
     let ubs = "☃".as_bytes();
     let ubs = "hello there! this is a very long string".as_bytes();

tests/ui/string_lit_as_bytes.rs

@@ -1,8 +1,18 @@
 //@run-rustfix
+//@aux-build:macro_rules.rs
 
 #![allow(dead_code, unused_variables)]
 #![warn(clippy::string_lit_as_bytes)]
 
+#[macro_use]
+extern crate macro_rules;
+
+macro_rules! b {
+    ($b:literal) => {
+        const B: &[u8] = $b.as_bytes();
+    };
+}
+
 fn str_lit_as_bytes() {
     let bs = "hello there".as_bytes();
 
@@ -11,6 +21,10 @@ fn str_lit_as_bytes() {
     let bs = "lit to string".to_string().into_bytes();
     let bs = "lit to owned".to_owned().into_bytes();
 
+    b!("warning");
+
+    string_lit_as_bytes!("no warning");
+
     // no warning, because these cannot be written as byte string literals:
     let ubs = "☃".as_bytes();
     let ubs = "hello there! this is a very long string".as_bytes();

tests/ui/string_lit_as_bytes.stderr

@@ -1,40 +1,51 @@
 error: calling `as_bytes()` on a string literal
-  --> $DIR/string_lit_as_bytes.rs:7:14
+  --> $DIR/string_lit_as_bytes.rs:17:14
    |
 LL |     let bs = "hello there".as_bytes();
    |              ^^^^^^^^^^^^^^^^^^^^^^^^ help: consider using a byte string literal instead: `b"hello there"`
    |
    = note: `-D clippy::string-lit-as-bytes` implied by `-D warnings`
 
 error: calling `as_bytes()` on a string literal
-  --> $DIR/string_lit_as_bytes.rs:9:14
+  --> $DIR/string_lit_as_bytes.rs:19:14
    |
 LL |     let bs = r###"raw string with 3# plus " ""###.as_bytes();
    |              ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: consider using a byte string literal instead: `br###"raw string with 3# plus " ""###`
 
 error: calling `into_bytes()` on a string literal
-  --> $DIR/string_lit_as_bytes.rs:11:14
+  --> $DIR/string_lit_as_bytes.rs:21:14
    |
 LL |     let bs = "lit to string".to_string().into_bytes();
    |              ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: consider using a byte string literal instead: `b"lit to string".to_vec()`
 
 error: calling `into_bytes()` on a string literal
-  --> $DIR/string_lit_as_bytes.rs:12:14
+  --> $DIR/string_lit_as_bytes.rs:22:14
    |
 LL |     let bs = "lit to owned".to_owned().into_bytes();
    |              ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: consider using a byte string literal instead: `b"lit to owned".to_vec()`
 
+error: calling `as_bytes()` on a string literal
+  --> $DIR/string_lit_as_bytes.rs:12:26
+   |
+LL |         const B: &[u8] = $b.as_bytes();
+   |                          ^^^^^^^^^^^^^ help: consider using a byte string literal instead: `b"warning"`
+...
+LL |     b!("warning");
+   |     ------------- in this macro invocation
+   |
+   = note: this error originates in the macro `b` (in Nightly builds, run with -Z macro-backtrace for more info)
+
 error: calling `as_bytes()` on `include_str!(..)`
-  --> $DIR/string_lit_as_bytes.rs:25:22
+  --> $DIR/string_lit_as_bytes.rs:39:22
    |
 LL |     let includestr = include_str!("string_lit_as_bytes.rs").as_bytes();
    |                      ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: consider using `include_bytes!(..)` instead: `include_bytes!("string_lit_as_bytes.rs")`
 
 error: calling `as_bytes()` on a string literal
-  --> $DIR/string_lit_as_bytes.rs:27:13
+  --> $DIR/string_lit_as_bytes.rs:41:13
    |
 LL |     let _ = "string with newline/t/n".as_bytes();
    |             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: consider using a byte string literal instead: `b"string with newline/t/n"`
 
-error: aborting due to 6 previous errors
+error: aborting due to 7 previous errors