[Bug]: await + 0 or await () become await 0 in strict mode

[p51lee]

Bug report

Version (complete output of terser -V or specific git commit)

$ terser -V
terser 5.15.1

Complete CLI command or minify() options used
I turned off the unsafe option.

$ terser input.js -c unsafe=false

terser input

"use strict";
await + 0;

or

"use strict";
await ( ) ;

terser output or error

"use strict";await 0;

Expected result
Input codes throw ReferenceError:

$ node -e '"use strict"; await + 0;'
ReferenceError: await is not defined
    at [eval]:1:1
    at Script.runInThisContext (node:vm:129:12)
    at Object.runInThisContext (node:vm:313:38)
    at node:internal/process/execution:79:19
    at [eval]-wrapper:6:22
    at evalScript (node:internal/process/execution:78:60)
    at node:internal/main/eval_string:28:3

Node.js v18.11.0

$ node -e '"use strict"; await ( ) ;'
ReferenceError: await is not defined
...

but output code throws SyntaxError:

$ node -e '"use strict"; await 0 ;'
[eval]:1
"use strict"; await 0 ;
              ^^^^^

SyntaxError: await is only valid in async functions and the top level bodies of modules
    at new Script (node:vm:100:7)
    at createScript (node:vm:265:10)
    at Object.runInThisContext (node:vm:313:10)
    at node:internal/process/execution:79:19
    at [eval]-wrapper:6:22
    at evalScript (node:internal/process/execution:78:60)
    at node:internal/main/eval_string:28:3

Node.js v18.11.0

[fabiosantoscode]

I'm not even sure what the expected behavior is in the top level.

await ( ) is clearly not an await expression, it would only be reasonable to mix it up with a function call.

But for await + 0 or await ( 0 ) I think Terser needs to know the context of the code it's looking at.

Terser might be looking at module code, or not, and those await constructs mean different things in those contexts.

[fabiosantoscode]

I think the way I'll solve this is by allowing await on the top-level, at least by default, that is to assume the source code is an ES module for the case of await.