Add check for line!

Author: tesuji

clippy_lints/src/misc_early.rs

@@ -1,5 +1,6 @@
 use crate::utils::{
-    constants, snippet, snippet_opt, span_help_and_lint, span_lint, span_lint_and_sugg, span_lint_and_then,
+    constants, is_direct_expn_of, snippet, snippet_opt, span_help_and_lint, span_lint, span_lint_and_sugg,
+    span_lint_and_then,
 };
 use if_chain::if_chain;
 use rustc::lint::{in_external_macro, EarlyContext, EarlyLintPass, LintArray, LintContext, LintPass};
@@ -390,6 +391,22 @@ impl EarlyLintPass for MiscEarlyLints {
 
 impl MiscEarlyLints {
     fn check_lit(self, cx: &EarlyContext<'_>, lit: &Lit) {
+        use crate::utils::is_expn_of;
+
+        // The `line!()` macro is compiler built-in and a special case for these lints.
+        if is_expn_of(lit.span, "line").is_some() {
+            span_lint_and_sugg(
+                cx,
+                UNSEPARATED_LITERAL_SUFFIX,
+                lit.span,
+                "well! that weird",
+                "add an underscore",
+                "DEBUG: ok dookey".to_string(),
+                Applicability::MachineApplicable,
+            );
+            return;
+        }
+
         let lit_snip = match snippet_opt(cx, lit.span) {
             Some(snip) => snip,
             None => return,

tests/ui/unseparated_prefix_literals.fixed

@@ -5,7 +5,7 @@
 
 macro_rules! lit_from_macro {
     () => {
-        42_usize
+        42_usize // <| Lint here instead
     };
 }
 

tests/ui/unseparated_prefix_literals.rs

@@ -5,7 +5,7 @@
 
 macro_rules! lit_from_macro {
     () => {
-        42usize
+        42usize // <| Lint here instead
     };
 }
 
@@ -24,7 +24,9 @@ fn main() {
     let _failf1 = 1.5f32;
     let _failf2 = 1f32;
 
+    // Test for macro
+    let _ = lit_from_macro!(); // Do NOT lint here |^
+
     // Counter example
     let _ = line!();
-    let _ = lit_from_macro!();
 }