crucible-wasm: Add elem-related test case

We have recently made some changes to the way `crucible-wasm` handled element
segments, so this test case helps ensure that we have not broken anything that
used to work before.

crucible-wasm/test-data/elem.good

@@ -0,0 +1 @@
+[Crux] Overall status: Valid.

crucible-wasm/test-data/elem.wast

@@ -0,0 +1,141 @@
+;; Test the element section
+;;
+;; Adapted from the elem test case in
+;;
+;;   https://github.com/WebAssembly/spec/blob/351d8b1026a2a820e88baae54557c43e775fd5a5/test/core/elem.wast
+
+;; Syntax
+(module
+  (table $t 10 funcref)
+  (func $f)
+  (func $g)
+
+  ;; Active
+  (elem (table $t) (i32.const 0) funcref)
+  (elem (table $t) (i32.const 0) funcref (ref.func $f) (ref.func $g))
+  (elem (table $t) (i32.const 0) func)
+  (elem (table $t) (i32.const 0) func $f $g)
+  (elem (table $t) (offset (i32.const 0)) funcref)
+  (elem (table $t) (offset (i32.const 0)) func $f $g)
+  (elem (table 0) (i32.const 0) func)
+  (elem (table 0x0) (i32.const 0) func $f $f)
+  (elem (table 0x000) (offset (i32.const 0)) func)
+  (elem (table 0) (offset (i32.const 0)) func $f $f)
+  (elem (table $t) (i32.const 0) func)
+  (elem (table $t) (i32.const 0) func $f $f)
+  (elem (table $t) (offset (i32.const 0)) func)
+  (elem (table $t) (offset (i32.const 0)) func $f $f)
+  (elem (offset (i32.const 0)))
+  (elem (offset (i32.const 0)) funcref (ref.func $f) (ref.func $g))
+  (elem (offset (i32.const 0)) func $f $f)
+  (elem (offset (i32.const 0)) $f $f)
+  (elem (i32.const 0))
+  (elem (i32.const 0) funcref (ref.func $f) (ref.func $g))
+  (elem (i32.const 0) func $f $f)
+  (elem (i32.const 0) $f $f)
+  (elem (i32.const 0) funcref (item (ref.func $f)) (item (ref.func $g)))
+
+  (elem $a1 (table $t) (i32.const 0) funcref)
+  (elem $a2 (table $t) (i32.const 0) funcref (ref.func $f) (ref.func $g))
+  (elem $a3 (table $t) (i32.const 0) func)
+  (elem $a4 (table $t) (i32.const 0) func $f $g)
+  (elem $a9 (table $t) (offset (i32.const 0)) funcref)
+  (elem $a10 (table $t) (offset (i32.const 0)) func $f $g)
+  (elem $a11 (table 0) (i32.const 0) func)
+  (elem $a12 (table 0x0) (i32.const 0) func $f $f)
+  (elem $a13 (table 0x000) (offset (i32.const 0)) func)
+  (elem $a14 (table 0) (offset (i32.const 0)) func $f $f)
+  (elem $a15 (table $t) (i32.const 0) func)
+  (elem $a16 (table $t) (i32.const 0) func $f $f)
+  (elem $a17 (table $t) (offset (i32.const 0)) func)
+  (elem $a18 (table $t) (offset (i32.const 0)) func $f $f)
+  (elem $a19 (offset (i32.const 0)))
+  (elem $a20 (offset (i32.const 0)) funcref (ref.func $f) (ref.func $g))
+  (elem $a21 (offset (i32.const 0)) func $f $f)
+  (elem $a22 (offset (i32.const 0)) $f $f)
+  (elem $a23 (i32.const 0))
+  (elem $a24 (i32.const 0) funcref (ref.func $f) (ref.func $g))
+  (elem $a25 (i32.const 0) func $f $f)
+  (elem $a26 (i32.const 0) $f $f)
+)
+
+(module
+  (func $f)
+  (func $g)
+
+  (table $t funcref (elem (ref.func $f) (ref.func $g) (ref.func $g)))
+)
+
+
+;; Basic use
+
+(module
+  (table 10 funcref)
+  (func $f)
+  (elem (i32.const 0) $f)
+)
+
+(module
+  (table 10 funcref)
+  (func $f)
+  (elem (i32.const 0) $f)
+  (elem (i32.const 3) $f)
+  (elem (i32.const 7) $f)
+  (elem (i32.const 5) $f)
+  (elem (i32.const 3) $f)
+)
+
+(module
+  (type $out-i32 (func (result i32)))
+  (table 10 funcref)
+  (elem (i32.const 7) $const-i32-a)
+  (elem (i32.const 9) $const-i32-b)
+  (func $const-i32-a (type $out-i32) (i32.const 65))
+  (func $const-i32-b (type $out-i32) (i32.const 66))
+  (func (export "call-7") (type $out-i32)
+    (call_indirect (type $out-i32) (i32.const 7))
+  )
+  (func (export "call-9") (type $out-i32)
+    (call_indirect (type $out-i32) (i32.const 9))
+  )
+)
+(assert_return (invoke "call-7") (i32.const 65))
+(assert_return (invoke "call-9") (i32.const 66))
+
+;; Corner cases
+
+(module
+  (table 10 funcref)
+  (func $f)
+  (elem (i32.const 9) $f)
+)
+
+(module
+  (table 0 funcref)
+  (elem (i32.const 0))
+)
+
+(module
+  (table 0 0 funcref)
+  (elem (i32.const 0))
+)
+
+(module
+  (table 20 funcref)
+  (elem (i32.const 20))
+)
+
+;; Two elements target the same slot
+
+(module
+  (type $out-i32 (func (result i32)))
+  (table 10 funcref)
+  (elem (i32.const 9) $const-i32-a)
+  (elem (i32.const 9) $const-i32-b)
+  (func $const-i32-a (type $out-i32) (i32.const 65))
+  (func $const-i32-b (type $out-i32) (i32.const 66))
+  (func (export "call-overwritten") (type $out-i32)
+    (call_indirect (type $out-i32) (i32.const 9))
+  )
+)
+(assert_return (invoke "call-overwritten") (i32.const 66))