The compilation result of components may have inserted template
functions into the constant pool, which would be inserted into the Babel
AST upon program exit. Babel will then proceed with visiting this newly
inserted subtree, but we have already cleaned up the linker instance
when exiting the program. Any call expressions within the template
functions would then fail to be processed, as a file linker would no
longer be available.
Since the inserted AST subtree is known not to contain yet more partial
declarations, it is safe to skip visiting call expressions when no
file linker is available.
PR Close#39707
This commit adds the basic building blocks for linking partial declarations.
In particular it provides a generic `FileLinker` class that delegates to
a set of (not yet implemented) `PartialLinker` classes.
The Babel plugin makes use of this `FileLinker` providing concrete classes
for `AstHost` and `AstFactory` that work with Babel AST. It can be created
with the following code:
```ts
const plugin = createEs2015LinkerPlugin({ /* options */ });
```
PR Close#39116
