diff --git a/src/Sema.zig b/src/Sema.zig
index 37fdf0adb5..7a1885d652 100644
--- a/src/Sema.zig
+++ b/src/Sema.zig
@@ -2228,8 +2228,20 @@ fn failWithModRemNegative(sema: *Sema, block: *Block, src: LazySrcLoc, lhs_ty: T
     });
 }
 
-fn failWithExpectedOptionalType(sema: *Sema, block: *Block, src: LazySrcLoc, optional_ty: Type) CompileError {
-    return sema.fail(block, src, "expected optional type, found '{}'", .{optional_ty.fmt(sema.mod)});
+fn failWithExpectedOptionalType(sema: *Sema, block: *Block, src: LazySrcLoc, non_optional_ty: Type) CompileError {
+    const mod = sema.mod;
+    const msg = msg: {
+        const msg = try sema.errMsg(block, src, "expected optional type, found '{}'", .{
+            non_optional_ty.fmt(mod),
+        });
+        errdefer msg.destroy(sema.gpa);
+        if (non_optional_ty.zigTypeTag(mod) == .ErrorUnion) {
+            try sema.errNote(block, src, msg, "consider using 'try', 'catch', or 'if'", .{});
+        }
+        try addDeclaredHereNote(sema, msg, non_optional_ty);
+        break :msg msg;
+    };
+    return sema.failWithOwnedErrorMsg(block, msg);
 }
 
 fn failWithArrayInitNotSupported(sema: *Sema, block: *Block, src: LazySrcLoc, ty: Type) CompileError {
@@ -3557,9 +3569,10 @@ fn ensureResultUsed(
     const mod = sema.mod;
     switch (ty.zigTypeTag(mod)) {
         .Void, .NoReturn => return,
-        .ErrorSet, .ErrorUnion => {
+        .ErrorSet => return sema.fail(block, src, "error set is ignored", .{}),
+        .ErrorUnion => {
             const msg = msg: {
-                const msg = try sema.errMsg(block, src, "error is ignored", .{});
+                const msg = try sema.errMsg(block, src, "error union is ignored", .{});
                 errdefer msg.destroy(sema.gpa);
                 try sema.errNote(block, src, msg, "consider using 'try', 'catch', or 'if'", .{});
                 break :msg msg;
@@ -3571,7 +3584,7 @@ fn ensureResultUsed(
                 const msg = try sema.errMsg(block, src, "value of type '{}' ignored", .{ty.fmt(sema.mod)});
                 errdefer msg.destroy(sema.gpa);
                 try sema.errNote(block, src, msg, "all non-void values must be used", .{});
-                try sema.errNote(block, src, msg, "this error can be suppressed by assigning the value to '_'", .{});
+                try sema.errNote(block, src, msg, "to discard the value, assign it to '_'", .{});
                 break :msg msg;
             };
             return sema.failWithOwnedErrorMsg(block, msg);
@@ -3589,9 +3602,10 @@ fn zirEnsureResultNonError(sema: *Sema, block: *Block, inst: Zir.Inst.Index) Com
     const src = inst_data.src();
     const operand_ty = sema.typeOf(operand);
     switch (operand_ty.zigTypeTag(mod)) {
-        .ErrorSet, .ErrorUnion => {
+        .ErrorSet => return sema.fail(block, src, "error set is discarded", .{}),
+        .ErrorUnion => {
             const msg = msg: {
-                const msg = try sema.errMsg(block, src, "error is discarded", .{});
+                const msg = try sema.errMsg(block, src, "error union is discarded", .{});
                 errdefer msg.destroy(sema.gpa);
                 try sema.errNote(block, src, msg, "consider using 'try', 'catch', or 'if'", .{});
                 break :msg msg;
@@ -9038,7 +9052,7 @@ fn analyzeOptionalPayloadPtr(
 
     const opt_type = optional_ptr_ty.childType(zcu);
     if (opt_type.zigTypeTag(zcu) != .Optional) {
-        return sema.fail(block, src, "expected optional type, found '{}'", .{opt_type.fmt(zcu)});
+        return sema.failWithExpectedOptionalType(block, src, opt_type);
     }
 
     const child_type = opt_type.optionalChild(zcu);
@@ -9531,7 +9545,7 @@ fn handleExternLibName(
             return sema.fail(
                 block,
                 src_loc,
-                "dependency on dynamic library '{s}' requires enabling Position Independent Code. Fixed by '-l{s}' or '-fPIC'.",
+                "dependency on dynamic library '{s}' requires enabling Position Independent Code; fixed by '-l{s}' or '-fPIC'",
                 .{ lib_name, lib_name },
             );
         }
@@ -27875,6 +27889,9 @@ fn fieldCallBind(
             const decl = mod.declPtr(decl_idx);
             try mod.errNoteNonLazy(decl.srcLoc(mod), msg, "'{}' is not a member function", .{field_name.fmt(ip)});
         }
+        if (concrete_ty.zigTypeTag(mod) == .ErrorUnion) {
+            try sema.errNote(block, src, msg, "consider using 'try', 'catch', or 'if'", .{});
+        }
         break :msg msg;
     };
     return sema.failWithOwnedErrorMsg(block, msg);
diff --git a/test/cases/compile_errors/discarding_error_value.zig b/test/cases/compile_errors/discarding_error_value.zig
index c24d517d3e..eab3ecaf98 100644
--- a/test/cases/compile_errors/discarding_error_value.zig
+++ b/test/cases/compile_errors/discarding_error_value.zig
@@ -1,13 +1,18 @@
-export fn entry() void {
+export fn entry1() void {
     _ = foo();
 }
 fn foo() !void {
     return error.OutOfMemory;
 }
+export fn entry2() void {
+    const x: error{a} = undefined;
+    _ = x;
+}
 
 // error
 // backend=stage2
 // target=native
 //
-// :2:12: error: error is discarded
+// :2:12: error: error union is discarded
 // :2:12: note: consider using 'try', 'catch', or 'if'
+// :9:9: error: error set is discarded
diff --git a/test/cases/compile_errors/expected_optional_type_got_container.zig b/test/cases/compile_errors/expected_optional_type_got_container.zig
new file mode 100644
index 0000000000..12bb629629
--- /dev/null
+++ b/test/cases/compile_errors/expected_optional_type_got_container.zig
@@ -0,0 +1,16 @@
+export fn foo() void {
+    while (bar()) |x| {
+        _ = x;
+    }
+}
+const X = enum { a };
+fn bar() X {
+    return .a;
+}
+
+// error
+// backend=stage2
+// target=native
+//
+// :2:15: error: expected optional type, found 'tmp.X'
+// :6:11: note: enum declared here
diff --git a/test/cases/compile_errors/for_loop_body_expression_ignored.zig b/test/cases/compile_errors/for_loop_body_expression_ignored.zig
index a0247139ea..9c5e381e63 100644
--- a/test/cases/compile_errors/for_loop_body_expression_ignored.zig
+++ b/test/cases/compile_errors/for_loop_body_expression_ignored.zig
@@ -23,13 +23,13 @@ export fn f4() void {
 //
 // :5:30: error: value of type 'usize' ignored
 // :5:30: note: all non-void values must be used
-// :5:30: note: this error can be suppressed by assigning the value to '_'
+// :5:30: note: to discard the value, assign it to '_'
 // :9:30: error: value of type 'usize' ignored
 // :9:30: note: all non-void values must be used
-// :9:30: note: this error can be suppressed by assigning the value to '_'
+// :9:30: note: to discard the value, assign it to '_'
 // :13:31: error: value of type 'bool' ignored
 // :13:31: note: all non-void values must be used
-// :13:31: note: this error can be suppressed by assigning the value to '_'
+// :13:31: note: to discard the value, assign it to '_'
 // :16:42: error: value of type 'usize' ignored
 // :16:42: note: all non-void values must be used
-// :16:42: note: this error can be suppressed by assigning the value to '_'
+// :16:42: note: to discard the value, assign it to '_'
diff --git a/test/cases/compile_errors/generic_instantiation_failure.zig b/test/cases/compile_errors/generic_instantiation_failure.zig
index 42e4c4e8c8..d820f8f410 100644
--- a/test/cases/compile_errors/generic_instantiation_failure.zig
+++ b/test/cases/compile_errors/generic_instantiation_failure.zig
@@ -24,4 +24,4 @@ pub export fn entry() void {
 //
 // :18:43: error: value of type 'type' ignored
 // :18:43: note: all non-void values must be used
-// :18:43: note: this error can be suppressed by assigning the value to '_'
+// :18:43: note: to discard the value, assign it to '_'
diff --git a/test/cases/compile_errors/ignored_assert-err-ok_return_value.zig b/test/cases/compile_errors/ignored_assert-err-ok_return_value.zig
index 1257636622..abe2b006b7 100644
--- a/test/cases/compile_errors/ignored_assert-err-ok_return_value.zig
+++ b/test/cases/compile_errors/ignored_assert-err-ok_return_value.zig
@@ -11,4 +11,4 @@ fn bar() anyerror!i32 {
 //
 // :2:11: error: value of type 'i32' ignored
 // :2:11: note: all non-void values must be used
-// :2:11: note: this error can be suppressed by assigning the value to '_'
+// :2:11: note: to discard the value, assign it to '_'
diff --git a/test/cases/compile_errors/ignored_comptime_statement_value.zig b/test/cases/compile_errors/ignored_comptime_statement_value.zig
index 2067f3b716..4dd0e0fc39 100644
--- a/test/cases/compile_errors/ignored_comptime_statement_value.zig
+++ b/test/cases/compile_errors/ignored_comptime_statement_value.zig
@@ -10,4 +10,4 @@ export fn foo() void {
 //
 // :3:9: error: value of type 'comptime_int' ignored
 // :3:9: note: all non-void values must be used
-// :3:9: note: this error can be suppressed by assigning the value to '_'
+// :3:9: note: to discard the value, assign it to '_'
diff --git a/test/cases/compile_errors/ignored_comptime_value.zig b/test/cases/compile_errors/ignored_comptime_value.zig
index 3414d0861f..ed7eb80b50 100644
--- a/test/cases/compile_errors/ignored_comptime_value.zig
+++ b/test/cases/compile_errors/ignored_comptime_value.zig
@@ -14,7 +14,7 @@ fn bar() u8 {
 //
 // :2:5: error: value of type 'comptime_int' ignored
 // :2:5: note: all non-void values must be used
-// :2:5: note: this error can be suppressed by assigning the value to '_'
+// :2:5: note: to discard the value, assign it to '_'
 // :5:5: error: value of type 'u8' ignored
 // :5:5: note: all non-void values must be used
-// :5:5: note: this error can be suppressed by assigning the value to '_'
+// :5:5: note: to discard the value, assign it to '_'
diff --git a/test/cases/compile_errors/ignored_deferred_function_call.zig b/test/cases/compile_errors/ignored_deferred_function_call.zig
index 9537255d33..90c978b40f 100644
--- a/test/cases/compile_errors/ignored_deferred_function_call.zig
+++ b/test/cases/compile_errors/ignored_deferred_function_call.zig
@@ -5,9 +5,17 @@ fn bar() anyerror!i32 {
     return 0;
 }
 
+export fn foo2() void {
+    defer bar2();
+}
+fn bar2() anyerror {
+    return error.a;
+}
+
 // error
 // backend=stage2
 // target=native
 //
-// :2:14: error: error is ignored
+// :2:14: error: error union is ignored
 // :2:14: note: consider using 'try', 'catch', or 'if'
+// :9:15: error: error set is ignored
diff --git a/test/cases/compile_errors/ignored_deferred_statement_value.zig b/test/cases/compile_errors/ignored_deferred_statement_value.zig
index 1f42efc3f5..70b88a4deb 100644
--- a/test/cases/compile_errors/ignored_deferred_statement_value.zig
+++ b/test/cases/compile_errors/ignored_deferred_statement_value.zig
@@ -10,4 +10,4 @@ export fn foo() void {
 //
 // :3:9: error: value of type 'comptime_int' ignored
 // :3:9: note: all non-void values must be used
-// :3:9: note: this error can be suppressed by assigning the value to '_'
+// :3:9: note: to discard the value, assign it to '_'
diff --git a/test/cases/compile_errors/ignored_expression_in_while_continuation.zig b/test/cases/compile_errors/ignored_expression_in_while_continuation.zig
index 4fa396190a..ca1b60da5e 100644
--- a/test/cases/compile_errors/ignored_expression_in_while_continuation.zig
+++ b/test/cases/compile_errors/ignored_expression_in_while_continuation.zig
@@ -15,13 +15,21 @@ fn bad() anyerror!void {
     return error.Bad;
 }
 
+export fn d() void {
+    while (true) : (bad2()) {}
+}
+fn bad2() anyerror {
+    return error.Bad;
+}
+
 // error
 // backend=stage2
 // target=native
 //
-// :2:24: error: error is ignored
+// :2:24: error: error union is ignored
 // :2:24: note: consider using 'try', 'catch', or 'if'
-// :7:25: error: error is ignored
+// :7:25: error: error union is ignored
 // :7:25: note: consider using 'try', 'catch', or 'if'
-// :12:25: error: error is ignored
+// :12:25: error: error union is ignored
 // :12:25: note: consider using 'try', 'catch', or 'if'
+// :19:25: error: error set is ignored
diff --git a/test/cases/compile_errors/ignored_return_value.zig b/test/cases/compile_errors/ignored_return_value.zig
index 08424c4fe9..f721bc8655 100644
--- a/test/cases/compile_errors/ignored_return_value.zig
+++ b/test/cases/compile_errors/ignored_return_value.zig
@@ -11,4 +11,4 @@ fn bar() i32 {
 //
 // :2:8: error: value of type 'i32' ignored
 // :2:8: note: all non-void values must be used
-// :2:8: note: this error can be suppressed by assigning the value to '_'
+// :2:8: note: to discard the value, assign it to '_'
diff --git a/test/cases/compile_errors/ignored_statement_value.zig b/test/cases/compile_errors/ignored_statement_value.zig
index c73da84420..6c4ff442c5 100644
--- a/test/cases/compile_errors/ignored_statement_value.zig
+++ b/test/cases/compile_errors/ignored_statement_value.zig
@@ -8,4 +8,4 @@ export fn foo() void {
 //
 // :2:5: error: value of type 'comptime_int' ignored
 // :2:5: note: all non-void values must be used
-// :2:5: note: this error can be suppressed by assigning the value to '_'
+// :2:5: note: to discard the value, assign it to '_'
diff --git a/test/cases/compile_errors/method_call_on_error_union.zig b/test/cases/compile_errors/method_call_on_error_union.zig
new file mode 100644
index 0000000000..4ce6b3baa8
--- /dev/null
+++ b/test/cases/compile_errors/method_call_on_error_union.zig
@@ -0,0 +1,21 @@
+const X = struct {
+    fn init() !X {
+        return error.a;
+    }
+
+    fn a(x: X) void {
+        _ = x;
+    }
+};
+
+export fn entry() void {
+    const x = X.init();
+    x.a();
+}
+
+// error
+// backend=stage2
+// target=native
+//
+// :13:6: error: no field or member function named 'a' in '@typeInfo(@typeInfo(@TypeOf(tmp.X.init)).Fn.return_type.?).ErrorUnion.error_set!tmp.X'
+// :13:6: note: consider using 'try', 'catch', or 'if'
diff --git a/test/cases/compile_errors/while_expected_optional_got_error_union.zig b/test/cases/compile_errors/while_expected_optional_got_error_union.zig
index 7bde2c866d..1b4a64770b 100644
--- a/test/cases/compile_errors/while_expected_optional_got_error_union.zig
+++ b/test/cases/compile_errors/while_expected_optional_got_error_union.zig
@@ -12,3 +12,4 @@ fn bar() anyerror!i32 {
 // target=native
 //
 // :2:15: error: expected optional type, found 'anyerror!i32'
+// :2:15: note: consider using 'try', 'catch', or 'if'
diff --git a/test/cases/compile_errors/while_loop_body_expression_ignored.zig b/test/cases/compile_errors/while_loop_body_expression_ignored.zig
index b3e83f202a..dae546df02 100644
--- a/test/cases/compile_errors/while_loop_body_expression_ignored.zig
+++ b/test/cases/compile_errors/while_loop_body_expression_ignored.zig
@@ -32,16 +32,16 @@ export fn f5() void {
 //
 // :5:25: error: value of type 'usize' ignored
 // :5:25: note: all non-void values must be used
-// :5:25: note: this error can be suppressed by assigning the value to '_'
+// :5:25: note: to discard the value, assign it to '_'
 // :10:26: error: value of type 'usize' ignored
 // :10:26: note: all non-void values must be used
-// :10:26: note: this error can be suppressed by assigning the value to '_'
+// :10:26: note: to discard the value, assign it to '_'
 // :15:26: error: value of type 'usize' ignored
 // :15:26: note: all non-void values must be used
-// :15:26: note: this error can be suppressed by assigning the value to '_'
+// :15:26: note: to discard the value, assign it to '_'
 // :20:23: error: value of type 'bool' ignored
 // :20:23: note: all non-void values must be used
-// :20:23: note: this error can be suppressed by assigning the value to '_'
+// :20:23: note: to discard the value, assign it to '_'
 // :25:34: error: value of type 'usize' ignored
 // :25:34: note: all non-void values must be used
-// :25:34: note: this error can be suppressed by assigning the value to '_'
+// :25:34: note: to discard the value, assign it to '_'