From c49c20713c422c7936626195c1d9ff3a725c3704 Mon Sep 17 00:00:00 2001
From: Dan Gohman <sunfish@mozilla.com>
Date: Wed, 1 Aug 2018 13:33:54 -0700
Subject: [PATCH] Check for duplicate jump tables before performing any IR
 mutations.

This isn't fixing an actual bug, but it does make `add_jt` more
consistent with the other `add_*` functions.
---
 lib/reader/src/parser.rs | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/lib/reader/src/parser.rs b/lib/reader/src/parser.rs
index 3c9cb4c56f..bef37a86fd 100644
--- a/lib/reader/src/parser.rs
+++ b/lib/reader/src/parser.rs
@@ -233,11 +233,12 @@ impl<'a> Context<'a> {
 
     // Allocate a new jump table.
     fn add_jt(&mut self, jt: JumpTable, data: JumpTableData, loc: Location) -> ParseResult<()> {
+        self.map.def_jt(jt, loc)?;
         while self.function.jump_tables.next_key().index() <= jt.index() {
             self.function.create_jump_table(JumpTableData::new());
         }
         self.function.jump_tables[jt] = data;
-        self.map.def_jt(jt, loc)
+        Ok(())
     }
 
     // Resolve a reference to a jump table.