Auto merge of rust-lang#6959 - ebobrow:iss-6927-fix, r=camsteffen

Check for `.to_string().into_bytes()` in string_lit_to_bytes

fixes rust-lang#6927

changelog: Add a check for `into_bytes()` to string_lit_to_bytes lint

Author: bors

clippy_lints/src/strings.rs

@@ -284,6 +284,35 @@ impl<'tcx> LateLintPass<'tcx> for StringLitAsBytes {
                 }
             }
         }
+
+        if_chain! {
+            if let ExprKind::MethodCall(path, _, [recv], _) = &e.kind;
+            if path.ident.name == sym!(into_bytes);
+            if let ExprKind::MethodCall(path, _, [recv], _) = &recv.kind;
+            if matches!(&*path.ident.name.as_str(), "to_owned" | "to_string");
+            if let ExprKind::Lit(lit) = &recv.kind;
+            if let LitKind::Str(lit_content, _) = &lit.node;
+
+            if lit_content.as_str().is_ascii();
+            if lit_content.as_str().len() <= MAX_LENGTH_BYTE_STRING_LIT;
+            if !recv.span.from_expansion();
+            then {
+                let mut applicability = Applicability::MachineApplicable;
+
+                span_lint_and_sugg(
+                    cx,
+                    STRING_LIT_AS_BYTES,
+                    e.span,
+                    "calling `into_bytes()` on a string literal",
+                    "consider using a byte string literal instead",
+                    format!(
+                        "b{}.to_vec()",
+                        snippet_with_applicability(cx, recv.span, r#""..""#, &mut applicability)
+                    ),
+                    applicability,
+                );
+            }
+        }
     }
 }
 

tests/ui/string_lit_as_bytes.fixed

@@ -8,10 +8,16 @@ fn str_lit_as_bytes() {
 
     let bs = br###"raw string with 3# plus " ""###;
 
+    let bs = b"lit to string".to_vec();
+    let bs = b"lit to owned".to_vec();
+
     // 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();
 
+    let ubs = "☃".to_string().into_bytes();
+    let ubs = "this is also too long and shouldn't be fixed".to_string().into_bytes();
+
     let strify = stringify!(foobar).as_bytes();
 
     let current_version = env!("CARGO_PKG_VERSION").as_bytes();

tests/ui/string_lit_as_bytes.rs

@@ -8,10 +8,16 @@ fn str_lit_as_bytes() {
 
     let bs = r###"raw string with 3# plus " ""###.as_bytes();
 
+    let bs = "lit to string".to_string().into_bytes();
+    let bs = "lit to owned".to_owned().into_bytes();
+
     // 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();
 
+    let ubs = "☃".to_string().into_bytes();
+    let ubs = "this is also too long and shouldn't be fixed".to_string().into_bytes();
+
     let strify = stringify!(foobar).as_bytes();
 
     let current_version = env!("CARGO_PKG_VERSION").as_bytes();

tests/ui/string_lit_as_bytes.stderr

@@ -12,17 +12,29 @@ error: calling `as_bytes()` on a string literal
 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
+   |
+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
+   |
+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 `include_str!(..)`
-  --> $DIR/string_lit_as_bytes.rs:19:22
+  --> $DIR/string_lit_as_bytes.rs:25:22
    |
 LL |     let includestr = include_str!("entry_unfixable.rs").as_bytes();
    |                      ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: consider using `include_bytes!(..)` instead: `include_bytes!("entry_unfixable.rs")`
 
 error: calling `as_bytes()` on a string literal
-  --> $DIR/string_lit_as_bytes.rs:21:13
+  --> $DIR/string_lit_as_bytes.rs:27:13
    |
 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 4 previous errors
+error: aborting due to 6 previous errors