[analyzer] An explicitly instantiated instance method tearoff is parsed as starting with a prefix

[eernstg]

Consider the following program:

class A {
  List<X> m<X>(X x) => [x];
}

extension FunctionApplier on Function {
  void applyAndPrint(List<Object?> positionalArguments) =>
      print(Function.apply(this, positionalArguments, const {}));
}

void main() {
  var a = A();
  a.m<int>.applyAndPrint([2]);
  a.m<String>.applyAndPrint(['three']);
}

This program is rejected (as of ef8add0) by dartanalyzer with the following error messages:

ERROR|COMPILE_TIME_ERROR|PREFIX_SHADOWED_BY_LOCAL_DECLARATION|/usr/local/google/home/eernst/lang/dart/scratch/202107/n038.dart|12|3|1|The prefix 'a' can't be used here because it is shadowed by a local declaration.
ERROR|COMPILE_TIME_ERROR|PREFIX_SHADOWED_BY_LOCAL_DECLARATION|/usr/local/google/home/eernst/lang/dart/scratch/202107/n038.dart|13|3|1|The prefix 'a' can't be used here because it is shadowed by a local declaration.

However, a is not an import prefix, it is a local variable. Presumably, the analyzer parser (or some other early step of the analysis) assumes that with constructs of the form <identifier> '.' <identifier> <typeArguments> '.', the first identifier must be an import prefix. That may have been true before constructor-tearoffs, but it isn't true with that feature, so the analyzer will need to investigate the situation more closely before it concludes that it is looking at an import prefix.

[devoncarew]

cc @srawlins

[srawlins]

Must handle new rewriting spelled out in @stereotype441 's Constructor Tearoff parsing strategy doc.

Analyzer's resolver gets the following from the parser:

• ExpressionStatementImpl: (a.m<int>.applyAndPrint([2]);)
  • ._expression: InstanceCreationExpressionImpl (a.m<int>.applyAndPrint([2]))
    • ._constructorName: ConstructorNameImpl (a.m<int>.applyAndPrint)
      • ._type: TypeNameImpl (a.m<int>)
        • ._name: PrefixedIdentifierImpl (a.m)
          • ._prefix: SimpleIdentifierImpl (a)
          • ._identifier: SimpleIdentifierImpl (m)
        • ._typeArguments: TypeArgumentListImpl (<int>)
      • ._name: SimpleIdentifierImpl (applyAndPrint)

This must be re-written into something like:

• ExpressionStatementImpl: (a.m<int>.applyAndPrint([2]);)
  • ._expression: MethodInvocationImpl (a.m<int>.applyAndPrint([2]))
    • ._target: FunctionReferenceImpl (a.m<int>)
      • ._function: PrefixedIdentifierImpl (a.m)
        • ._prefix: SimpleIdentifierImpl (a)
        • ._identifier: SimpleIdentifierImpl (m)
      • ._typeArguments: TypeArgumentListImpl (<int>)
    • ._methodName: SimpleIdentifierImpl (applyAndPrint)