make >> a compile error with any undef arg ; add a bunch of test cases

test/behavior/bit_shifting.zig

@@ -196,10 +196,3 @@ test "Saturating Shift Left" {
     try expectEqual(170141183460469231731687303715884105727, S.shlSat(@as(i128, 0x2fe6bc5448c55ce18252e2c9d4477750), 0x31));
     try expectEqual(0, S.shlSat(@as(i128, 0), 127));
 }
-
-test "shift by partially undef vector" {
-    comptime {
-        const a: @Vector(1, u8) = .{undefined};
-        _ = a >> @splat(4);
-    }
-}

test/cases/compile_errors/shl_exact_on_undefined_value.zig

@@ -0,0 +1,11 @@
+comptime {
+    var a: i64 = undefined;
+    var b: u6 = undefined;
+    _ = &a;
+    _ = &b;
+    _ = @shlExact(a, b);
+}
+
+// error
+//
+// :6:19: error: use of undefined value here causes illegal behavior

test/cases/compile_errors/shl_on_undefined_value.zig

@@ -0,0 +1,11 @@
+comptime {
+    var a: i64 = undefined;
+    var b: u6 = undefined;
+    _ = &a;
+    _ = &b;
+    _ = a << b;
+}
+
+// error
+//
+// :6:9: error: use of undefined value here causes illegal behavior

test/cases/compile_errors/shl_with_overflow_on_undefined_value.zig

@@ -0,0 +1,11 @@
+comptime {
+    var a: i64 = undefined;
+    var b: u6 = undefined;
+    _ = &a;
+    _ = &b;
+    _ = @shlWithOverflow(a, b);
+}
+
+// error
+//
+// :6:26: error: use of undefined value here causes illegal behavior

test/cases/compile_errors/shr_exact_on_undefined_value.zig

@@ -0,0 +1,11 @@
+comptime {
+    var a: i64 = undefined;
+    var b: u6 = undefined;
+    _ = &a;
+    _ = &b;
+    _ = @shrExact(a, b);
+}
+
+// error
+//
+// :6:19: error: use of undefined value here causes illegal behavior

test/cases/compile_errors/shr_on_undefined_value.zig

@@ -0,0 +1,11 @@
+comptime {
+    var a: i64 = undefined;
+    var b: u6 = undefined;
+    _ = &a;
+    _ = &b;
+    _ = a >> b;
+}
+
+// error
+//
+// :6:9: error: use of undefined value here causes illegal behavior