From 7ad10422793e56dcd50a4254beb8fc9d6c7f5eae Mon Sep 17 00:00:00 2001
From: Andrew Kelley <andrew@ziglang.org>
Date: Sat, 24 Jun 2023 13:03:51 -0700
Subject: [PATCH] Revert "fix parseInt failing when a correct base is given"

This reverts commit fa6cea22bf9cd5ff6a9dd882166cf7e479acfd6c.

Apologies for the merge. I thought this was a bug fix, but I see that it
is implementing a proposal that I intended to reject.
---
 lib/std/fmt.zig | 45 ++++++++++++++++++++-------------------------
 1 file changed, 20 insertions(+), 25 deletions(-)

diff --git a/lib/std/fmt.zig b/lib/std/fmt.zig
index 84e4fd648c..d983aba369 100644
--- a/lib/std/fmt.zig
+++ b/lib/std/fmt.zig
@@ -1753,14 +1753,6 @@ test "parseInt" {
     try std.testing.expect((try parseInt(u8, "255", 10)) == 255);
     try std.testing.expectError(error.Overflow, parseInt(u8, "256", 10));
 
-    // Test different bases
-    try std.testing.expect((try parseInt(i32, "0b10", 2)) == 0b10);
-    try std.testing.expect((try parseInt(i32, "0o10", 8)) == 0o10);
-    try std.testing.expect((try parseInt(i32, "0x10", 16)) == 0x10);
-    try std.testing.expect((try parseInt(i32, "10", 2)) == 0b10);
-    try std.testing.expect((try parseInt(i32, "10", 8)) == 0o10);
-    try std.testing.expect((try parseInt(i32, "10", 16)) == 0x10);
-
     // +0 and -0 should work for unsigned
     try std.testing.expect((try parseInt(u8, "-0", 10)) == 0);
     try std.testing.expect((try parseInt(u8, "+0", 10)) == 0);
@@ -1812,25 +1804,28 @@ fn parseWithSign(
 
     var buf_base = base;
     var buf_start = buf;
-
-    if (buf.len > 2 and buf[0] == '0') {
-        switch (std.ascii.toLower(buf[1])) {
-            'b' => {
-                if (base == 0) buf_base = 2;
-                buf_start = buf[2..];
-            },
-            'o' => {
-                if (base == 0) buf_base = 8;
-                buf_start = buf[2..];
-            },
-            'x' => {
-                if (base == 0) buf_base = 16;
-                buf_start = buf[2..];
-            },
-            else => {},
+    if (base == 0) {
+        // Treat is as a decimal number by default.
+        buf_base = 10;
+        // Detect the base by looking at buf prefix.
+        if (buf.len > 2 and buf[0] == '0') {
+            switch (std.ascii.toLower(buf[1])) {
+                'b' => {
+                    buf_base = 2;
+                    buf_start = buf[2..];
+                },
+                'o' => {
+                    buf_base = 8;
+                    buf_start = buf[2..];
+                },
+                'x' => {
+                    buf_base = 16;
+                    buf_start = buf[2..];
+                },
+                else => {},
+            }
         }
     }
-    if (buf_base == 0) buf_base = 10;
 
     const add = switch (sign) {
         .pos => math.add,