add bitwise shift eval tests

internal/luatest/bitwise_shift_test.go

@@ -0,0 +1,96 @@
+package luatest
+
+import (
+	"testing"
+
+	"github.com/realcoldfry/tslua/internal/transpiler"
+)
+
+// TestBitwiseShift_Eval pins down JS-conformant behavior of the shift operators
+// `<<`, `>>`, and `>>>` across all Lua targets where the operator is not
+// diagnosed. JS shift semantics: operands are coerced to int32 (`<<`, `>>`) or
+// uint32 (`>>>`), the shift count is masked to its low 5 bits, `>>` is
+// arithmetic, `>>>` is logical (unsigned).
+//
+// Targets where a shift is diagnosed (e.g. `>>` on 5.3+, all bitwise on
+// 5.0/5.1/universal) are skipped: the user opted out of those constructs.
+func TestBitwiseShift_Eval(t *testing.T) {
+	t.Parallel()
+
+	type shiftCase struct {
+		name string
+		expr string
+		want string
+	}
+
+	cases := []shiftCase{
+		{"-8 >> 1", "-8 >> 1", "-4"},
+		{"-1 >> 16", "-1 >> 16", "-1"},
+		// Shift count masked to 5 bits: 33 & 31 == 1, so equivalent to -8 >> 1.
+		{"-8 >> 33", "-8 >> 33", "-4"},
+		// Result truncated to int32: 1 << 31 wraps to INT32_MIN.
+		{"1 << 31", "1 << 31", "-2147483648"},
+		// Shift count masked to 5 bits: 32 & 31 == 0, so equivalent to 1 << 0.
+		{"1 << 32", "1 << 32", "1"},
+		// Shift count masked to 5 bits: 32 & 31 == 0, so equivalent to 1 >>> 0.
+		{"1 >>> 32", "1 >>> 32", "1"},
+		// `>>>` returns an unsigned value: -1 reinterpreted as uint32.
+		{"-1 >>> 0", "-1 >>> 0", "4294967295"},
+	}
+
+	// shiftKind classifies a case by its operator so we can skip cases that the
+	// transpiler diagnoses on a given target.
+	shiftKind := func(name string) string {
+		switch {
+		case containsOp(name, ">>>"):
+			return ">>>"
+		case containsOp(name, ">>"):
+			return ">>"
+		default:
+			return "<<"
+		}
+	}
+
+	type targetSpec struct {
+		name   string
+		target transpiler.LuaTarget
+		// diagnosed lists shift kinds that this target rejects with a
+		// diagnostic; those cases are skipped (treated as non-bugs).
+		diagnosed map[string]bool
+	}
+	targets := []targetSpec{
+		{"LuaJIT", transpiler.LuaTargetLuaJIT, nil},
+		// 5.0/5.1/universal: all bitwise ops are diagnosed; nothing to test.
+		{"5.2", transpiler.LuaTargetLua52, nil},
+		// 5.3+ diagnose `>>` (steers users to `>>>`); `<<` and `>>>` are emitted.
+		{"5.3", transpiler.LuaTargetLua53, map[string]bool{">>": true}},
+		{"5.4", transpiler.LuaTargetLua54, map[string]bool{">>": true}},
+		{"5.5", transpiler.LuaTargetLua55, map[string]bool{">>": true}},
+	}
+
+	for _, tc := range cases {
+		for _, tgt := range targets {
+			if tgt.diagnosed[shiftKind(tc.name)] {
+				continue
+			}
+			t.Run(tc.name+" ["+tgt.name+"]", func(t *testing.T) {
+				t.Parallel()
+				tsCode := "export const __result = " + tc.expr + ";"
+				results := TranspileTS(t, tsCode, Opts{LuaTarget: tgt.target})
+				got := RunLua(t, results, `mod["__result"]`, Opts{LuaTarget: tgt.target})
+				if got != tc.want {
+					t.Errorf("got %s, want %s", got, tc.want)
+				}
+			})
+		}
+	}
+}
+
+func containsOp(s, op string) bool {
+	for i := 0; i+len(op) <= len(s); i++ {
+		if s[i:i+len(op)] == op {
+			return true
+		}
+	}
+	return false
+}