Fix overflowing literal lint in loops

src/librustc/lint/mod.rs

@@ -35,7 +35,7 @@ use crate::util::nodemap::NodeMap;
 use errors::{DiagnosticBuilder, DiagnosticId};
 use std::{hash, ptr};
 use syntax::ast;
-use syntax::source_map::{MultiSpan, ExpnFormat};
+use syntax::source_map::{MultiSpan, ExpnFormat, CompilerDesugaringKind};
 use syntax::early_buffered_lints::BufferedEarlyLintId;
 use syntax::edition::Edition;
 use syntax::symbol::{Symbol, sym};
@@ -887,21 +887,22 @@ pub fn in_external_macro(sess: &Session, span: Span) -> bool {
     };
 
     match info.format {
-        ExpnFormat::MacroAttribute(..) => return true, // definitely a plugin
-        ExpnFormat::CompilerDesugaring(_) => return true, // well, it's "external"
-        ExpnFormat::MacroBang(..) => {} // check below
-    }
-
-    let def_site = match info.def_site {
-        Some(span) => span,
-        // no span for the def_site means it's an external macro
-        None => return true,
-    };
+        ExpnFormat::MacroAttribute(..) => true, // definitely a plugin
+        ExpnFormat::CompilerDesugaring(CompilerDesugaringKind::ForLoop) => false,
+        ExpnFormat::CompilerDesugaring(_) => true, // well, it's "external"
+        ExpnFormat::MacroBang(..) => {
+            let def_site = match info.def_site {
+                Some(span) => span,
+                // no span for the def_site means it's an external macro
+                None => return true,
+            };
 
-    match sess.source_map().span_to_snippet(def_site) {
-        Ok(code) => !code.starts_with("macro_rules"),
-        // no snippet = external macro or compiler-builtin expansion
-        Err(_) => true,
+            match sess.source_map().span_to_snippet(def_site) {
+                Ok(code) => !code.starts_with("macro_rules"),
+                // no snippet = external macro or compiler-builtin expansion
+                Err(_) => true,
+            }
+        }
     }
 }
 

src/test/ui/lint/deny-overflowing-literals.rs

@@ -1,4 +1,7 @@
 fn main() {
     let x: u8 = 256;
     //~^ error: literal out of range for `u8`
+
+    for _ in 0..256u8 {}
+    //~^ error: range endpoint is out of range for `u8`
 }

src/test/ui/lint/deny-overflowing-literals.stderr

@@ -6,5 +6,11 @@ LL |     let x: u8 = 256;
    |
    = note: #[deny(overflowing_literals)] on by default
 
-error: aborting due to previous error
+error: range endpoint is out of range for `u8`
+  --> $DIR/deny-overflowing-literals.rs:5:14
+   |
+LL |     for _ in 0..256u8 {}
+   |              ^^^^^^^^ help: use an inclusive range instead: `0..=255u8`
+
+error: aborting due to 2 previous errors
 

src/test/ui/unreachable/unreachable-loop-patterns.rs

@@ -19,4 +19,5 @@ impl Iterator for Void {
 fn main() {
     for _ in unimplemented!() as Void {}
     //~^ ERROR unreachable pattern
+    //~^^ ERROR unreachable pattern
 }

src/test/ui/unreachable/unreachable-loop-patterns.stderr

@@ -10,5 +10,11 @@ note: lint level defined here
 LL | #![deny(unreachable_patterns)]
    |         ^^^^^^^^^^^^^^^^^^^^
 
-error: aborting due to previous error
+error: unreachable pattern
+  --> $DIR/unreachable-loop-patterns.rs:20:14
+   |
+LL |     for _ in unimplemented!() as Void {}
+   |              ^^^^^^^^^^^^^^^^^^^^^^^^
+
+error: aborting due to 2 previous errors