Commit d78eda34c5

@@ -10078,13 +10078,21 @@ fn intCast(
             if (actual_info.signedness == .signed) {
                 // Reinterpret the sign-bit as part of the value. This will make
                 // negative differences (`operand` > `dest_max`) appear too big.
-                const unsigned_operand_ty = try mod.intType(.unsigned, actual_bits);
+                const unsigned_scalar_operand_ty = try mod.intType(.unsigned, actual_bits);
+                const unsigned_operand_ty = if (is_vector) try mod.vectorType(.{
+                    .len = dest_ty.vectorLen(mod),
+                    .child = unsigned_scalar_operand_ty.toIntern(),
+                }) else unsigned_scalar_operand_ty;
                 const diff_unsigned = try block.addBitCast(unsigned_operand_ty, diff);
 
                 // If the destination type is signed, then we need to double its
                 // range to account for negative values.
                 const dest_range_val = if (wanted_info.signedness == .signed) range_val: {
-                    const one = try mod.intValue(unsigned_operand_ty, 1);
+                    const one_scalar = try mod.intValue(unsigned_scalar_operand_ty, 1);
+                    const one = if (is_vector) (try mod.intern(.{ .aggregate = .{
+                        .ty = unsigned_operand_ty.toIntern(),
+                        .storage = .{ .repeated_elem = one_scalar.toIntern() },
+                    } })).toValue() else one_scalar;
                     const range_minus_one = try dest_max_val.shl(one, unsigned_operand_ty, sema.arena, mod);
                     break :range_val try sema.intAdd(range_minus_one, one, unsigned_operand_ty, undefined);
                 } else try mod.getCoerced(dest_max_val, unsigned_operand_ty);

@@ -2428,3 +2428,21 @@ test "result information is preserved through many nested structures" {
     try S.doTheTest();
     try comptime S.doTheTest();
 }
+
+test "@intCast vector of signed integer" {
+    if (builtin.zig_backend == .stage2_aarch64) return error.SkipZigTest; // TODO
+    if (builtin.zig_backend == .stage2_arm) return error.SkipZigTest; // TODO
+    if (builtin.zig_backend == .stage2_wasm) return error.SkipZigTest; // TODO
+    if (builtin.zig_backend == .stage2_sparc64) return error.SkipZigTest; // TODO
+    if (builtin.zig_backend == .stage2_spirv64) return error.SkipZigTest; // TODO
+    if (builtin.zig_backend == .stage2_c) return error.SkipZigTest; // TODO
+    if (builtin.zig_backend == .stage2_x86_64) return error.SkipZigTest; // TODO
+
+    var x: @Vector(4, i32) = .{ 1, 2, 3, 4 };
+    const y: @Vector(4, i8) = @intCast(x);
+
+    try expect(y[0] == 1);
+    try expect(y[1] == 2);
+    try expect(y[2] == 3);
+    try expect(y[3] == 4);
+}