Deserialize small numbers as integers in arbitrary_precision

Author: dtolnay

src/de.rs

@@ -864,6 +864,15 @@ impl<'de, R: Read<'de>> Deserializer<R> {
             buf.push('-');
         }
         self.scan_integer(&mut buf)?;
+        if positive {
+            if let Ok(unsigned) = buf.parse() {
+                return Ok(ParserNumber::U64(unsigned));
+            }
+        } else {
+            if let Ok(signed) = buf.parse() {
+                return Ok(ParserNumber::I64(signed));
+            }
+        }
         Ok(ParserNumber::String(buf))
     }
 

src/lib.rs

@@ -303,6 +303,7 @@
 #![doc(html_root_url = "https://docs.rs/serde_json/1.0.74")]
 // Ignored clippy lints
 #![allow(
+    clippy::collapsible_else_if,
     clippy::comparison_chain,
     clippy::deprecated_cfg_attr,
     clippy::doc_markdown,

tests/test.rs

@@ -715,11 +715,7 @@ fn test_parse_char() {
         ),
         (
             "10",
-            if cfg!(feature = "arbitrary_precision") {
-                "invalid type: number, expected a character at line 1 column 2"
-            } else {
-                "invalid type: integer `10`, expected a character at line 1 column 2"
-            },
+            "invalid type: integer `10`, expected a character at line 1 column 2",
         ),
     ]);
 
@@ -1203,11 +1199,7 @@ fn test_parse_struct() {
     test_parse_err::<Outer>(&[
         (
             "5",
-            if cfg!(feature = "arbitrary_precision") {
-                "invalid type: number, expected struct Outer at line 1 column 1"
-            } else {
-                "invalid type: integer `5`, expected struct Outer at line 1 column 1"
-            },
+            "invalid type: integer `5`, expected struct Outer at line 1 column 1",
         ),
         (
             "\"hello\"",