Merge da0eb66b67 into 87863a834b

src/Sema.zig

@@ -9092,11 +9092,57 @@ fn zirEnumFromInt(sema: *Sema, block: *Block, inst: Zir.Inst.Index) CompileError
 
     try sema.requireRuntimeBlock(block, src, operand_src);
     const result = try block.addTyOp(.intcast, dest_ty, operand);
-    if (block.wantSafety() and !dest_ty.isNonexhaustiveEnum(zcu) and
-        zcu.backendSupportsFeature(.is_named_enum_value))
-    {
-        const ok = try block.addUnOp(.is_named_enum_value, result);
-        try sema.addSafetyCheck(block, src, ok, .invalid_enum_value);
+    if (block.wantSafety()) {
+        if (dest_ty.isNonexhaustiveEnum(zcu)) {
+            // these checks are similar to those generated by `intCast`,
+            // except that `invalid_enum_value` is the panic reason for all
+            // failures.
+            const operand_ty = sema.typeOf(operand);
+            const operand_int_info = sema.typeOf(operand).intInfo(zcu);
+            const dest_tag_ty = dest_ty.intTagType(zcu);
+            const dest_int_info = dest_tag_ty.intInfo(zcu);
+            var ok: ?Air.Inst.Ref = null;
+            if (operand_int_info.bits > dest_int_info.bits) {
+                // narrowing cast; operand <= dest_max_int required, and operand >= 0 may be
+                // required if operand is signed and destination int is unsigned
+                const dest_max_int = Air.internedToRef((try dest_tag_ty.maxIntScalar(pt, operand_ty)).toIntern());
+                // operand <= maxInt(dest_tag_ty)
+                const le_check = try block.addBinOp(.cmp_lte, operand, dest_max_int);
+                if (operand_int_info.signedness == .signed) {
+                    const dest_min_int = Air.internedToRef((try dest_tag_ty.minIntScalar(pt, operand_ty)).toIntern());
+                    const ge_zero_check = try block.addBinOp(.cmp_gte, operand, dest_min_int);
+                    // operand >= minInt(dest_tag_ty) and operand <= maxInt(dest_tag_ty)
+                    ok = try block.addBinOp(.bool_and, le_check, ge_zero_check);
+                } else {
+                    ok = le_check;
+                }
+            } else if (operand_int_info.bits == dest_int_info.bits) {
+                // checks are only needed here if the operand type's sign differs
+                // from the destination type's tag's sign.
+                if (operand_int_info.signedness == .unsigned and dest_int_info.signedness == .signed) {
+                    const dest_max_int = try dest_tag_ty.maxIntScalar(pt, operand_ty);
+                    // operand <= maxInt(dest_tag_ty)
+                    ok = try block.addBinOp(.cmp_lte, operand, Air.internedToRef(dest_max_int.toIntern()));
+                } else if (operand_int_info.signedness == .signed and dest_int_info.signedness == .unsigned) {
+                    const zero = try pt.intValue_i64(operand_ty, 0);
+                    // operand >= 0
+                    ok = try block.addBinOp(.cmp_gte, operand, Air.internedToRef(zero.toIntern()));
+                } // else => operand and destination int are the same type; no checks needed
+            } else {
+                // extending cast; no checks needed unless the operand is signed
+                // and the destination is unsigned
+                if (operand_int_info.signedness == .signed and dest_int_info.signedness == .unsigned) {
+                    const zero = try pt.intValue_i64(operand_ty, 0);
+                    // operand >= 0
+                    ok = try block.addBinOp(.cmp_gte, operand, Air.internedToRef(zero.toIntern()));
+                }
+            }
+            if (ok) |check|
+                try sema.addSafetyCheck(block, src, check, .invalid_enum_value);
+        } else if (zcu.backendSupportsFeature(.is_named_enum_value)) {
+            const ok = try block.addUnOp(.is_named_enum_value, result);
+            try sema.addSafetyCheck(block, src, ok, .invalid_enum_value);
+        }
     }
     return result;
 }

test/cases/enum_from_int_narrows_to_tag_type_nonexhaustive.zig

@@ -0,0 +1,30 @@
+const std = @import("std");
+
+const SignedWithVariants = enum(i4) { a, b, _ };
+
+const UnsignedWithVariants = enum(u4) { a, b, _ };
+
+const SignedEmpty = enum(i6) { _ };
+
+const UnsignedEmpty = enum(u6) { _ };
+
+pub fn main() void {
+    inline for (.{ SignedWithVariants, UnsignedWithVariants, SignedEmpty, UnsignedEmpty }) |EnumTy| {
+        const TagType = @typeInfo(EnumTy).@"enum".tag_type;
+        var v: isize = std.math.minInt(TagType);
+        while (v < std.math.maxInt(TagType)) : (v += 1) {
+            const variant = @as(EnumTy, @enumFromInt(v));
+            assert(@as(@TypeOf(v), @intCast(@intFromEnum(variant))) == v);
+        }
+        const max = std.math.maxInt(TagType);
+        const max_variant = @as(EnumTy, @enumFromInt(max));
+        assert(@as(@TypeOf(max), @intCast(@intFromEnum(max_variant))) == max);
+    }
+}
+
+fn assert(ok: bool) void {
+    if (!ok) unreachable;
+}
+
+// run
+// backend=stage2,llvm

test/cases/safety/invalid_nonexhaustive_enum_integer_value.zig

@@ -0,0 +1,20 @@
+const std = @import("std");
+
+pub fn panic(message: []const u8, _: ?*std.builtin.StackTrace, _: ?usize) noreturn {
+    if (std.mem.eql(u8, message, "invalid enum value")) {
+        std.process.exit(0);
+    }
+    std.process.exit(1);
+}
+
+pub fn main() void {
+    const E = enum(u4) { _ };
+    var invalid: u16 = 16;
+    _ = &invalid;
+    _ = @as(E, @enumFromInt(invalid));
+    std.process.exit(1);
+}
+
+// run
+// backend=llvm
+// target=native