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Revert "Add support for parsing simple nullable types"
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This reverts commit c5fd11b.

Reason for revert: Conditional expression lookahead may modify the token stream

Original change's description:
> Add support for parsing simple nullable types
> 
> ... as part of adding NNBD as outlined in
> dart-lang/language#110
> 
> This only supports parsing simple nullable types
> such as int? and List<int>? while subsequent CLs
> will add support for parsing more complex types.
> 
> Change-Id: I144858946cb115755af437299899c2631105bf8c
> Reviewed-on: https://dart-review.googlesource.com/c/87501
> Reviewed-by: Brian Wilkerson <[email protected]>
> Commit-Queue: Dan Rubel <[email protected]>

[email protected],[email protected]

Change-Id: Ie1f47e7384ff51159aa2ebeb21561455b8e6287f
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Reviewed-on: https://dart-review.googlesource.com/c/87620
Reviewed-by: Dan Rubel <[email protected]>
Commit-Queue: Dan Rubel <[email protected]>
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Dan Rubel authored and [email protected] committed Dec 18, 2018
1 parent c7e7cbd commit 48093f5
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Showing 4 changed files with 36 additions and 288 deletions.
28 changes: 10 additions & 18 deletions pkg/front_end/lib/src/fasta/parser/parser.dart
View file
Original file line number Diff line number Diff line change
Expand Up @@ -4489,7 +4489,11 @@ class Parser {
Token name = beforeName.next;
if (name.isIdentifier) {
TypeParamOrArgInfo typeParam = computeTypeParamOrArg(name);
Token next = typeParam.skip(name).next;
Token next = name;
if (typeParam != noTypeParamOrArg) {
next = typeParam.skip(next);
}
next = next.next;
if (optional('(', next)) {
if (looksLikeFunctionBody(next.endGroup.next)) {
return parseFunctionLiteral(
Expand Down Expand Up @@ -4869,10 +4873,8 @@ class Parser {
if (optional('!', token.next)) {
not = token = token.next;
}
TypeInfo typeInfo = computeType(token, true);
if (typeInfo.isConditionalExpressionStart(token, this)) {
typeInfo = typeInfo.asNonNullable;
}
// Ignore trailing `?` if there is one as it may be part of an expression
TypeInfo typeInfo = computeType(token, true).asNonNullableType();
token = typeInfo.ensureTypeNotVoid(token, this);
listener.handleIsOperator(operator, not);
return skipChainedAsIsOperators(token);
Expand All @@ -4886,10 +4888,8 @@ class Parser {
Token parseAsOperatorRest(Token token) {
Token operator = token = token.next;
assert(optional('as', operator));
TypeInfo typeInfo = computeType(token, true);
if (typeInfo.isConditionalExpressionStart(token, this)) {
typeInfo = typeInfo.asNonNullable;
}
// Ignore trailing `?` if there is one as it may be part of an expression
TypeInfo typeInfo = computeType(token, true).asNonNullableType();
token = typeInfo.ensureTypeNotVoid(token, this);
listener.handleAsOperator(operator);
return skipChainedAsIsOperators(token);
Expand All @@ -4908,11 +4908,7 @@ class Parser {
if (optional('!', next.next)) {
next = next.next;
}
TypeInfo typeInfo = computeType(next, true);
if (typeInfo.isConditionalExpressionStart(next, this)) {
typeInfo = typeInfo.asNonNullable;
}
token = typeInfo.skipType(next);
token = computeType(next, true).skipType(next);
next = token.next;
value = next.stringValue;
}
Expand Down Expand Up @@ -5033,10 +5029,6 @@ class Parser {
TypeInfo typeInfo,
bool onlyParseVariableDeclarationStart = false]) {
typeInfo ??= computeType(beforeType, false);
if (typeInfo.isConditionalExpressionStart(beforeType, this)) {
typeInfo = noType;
}

Token token = typeInfo.skipType(beforeType);
Token next = token.next;

Expand Down
45 changes: 9 additions & 36 deletions pkg/front_end/lib/src/fasta/parser/type_info.dart
View file
Original file line number Diff line number Diff line change
Expand Up @@ -19,12 +19,12 @@ import 'util.dart' show isOneOf, optional;
abstract class TypeInfo {
/// Return type info representing the receiver without the trailing `?`
/// or the receiver if the receiver does not represent a nullable type.
TypeInfo get asNonNullable;
TypeInfo asNonNullableType();

/// Return `true` if the tokens comprising the type represented by the
/// receiver could be interpreted as a valid standalone expression.
/// For example, `A` or `A.b` could be interpreted as type references
/// or expressions, while `A<T>` only looks like a type reference.
/// For example, `A` or `A.b` could be interpreted as a type references
/// or as expressions, while `A<T>` only looks like a type reference.
bool get couldBeExpression;

/// Call this function when the token after [token] must be a type (not void).
Expand All @@ -41,13 +41,6 @@ abstract class TypeInfo {
/// in valid code or during recovery.
Token ensureTypeOrVoid(Token token, Parser parser);

/// Return `true` if the tokens comprising the type represented by the
/// receiver are the start of a conditional expression.
/// For example, `A?` or `A.b?` could be the start of a conditional expression
/// and require arbitrary look ahead to determine if it is,
/// while `A<T>?` cannot be the start of a conditional expression.
bool isConditionalExpressionStart(Token token, Parser parser);

/// Call this function to parse an optional type (not void) after [token].
/// This function will call the appropriate event methods on the [Parser]'s
/// listener to handle the type. This may modify the token stream
Expand Down Expand Up @@ -206,19 +199,13 @@ TypeInfo computeType(final Token token, bool required,
// We've seen identifier `<` identifier `>`
next = typeParamOrArg.skip(next).next;
if (!isGeneralizedFunctionType(next)) {
if (optional('?', next) && typeParamOrArg == simpleTypeArgument1) {
if (required || looksLikeName(next.next)) {
// identifier `<` identifier `>` `?` identifier
return simpleNullableTypeWith1Argument;
}
if (required || looksLikeName(next)) {
// identifier `<` identifier `>` identifier
return typeParamOrArg.typeInfo;
} else {
if (required || looksLikeName(next)) {
// identifier `<` identifier `>` identifier
return typeParamOrArg.typeInfo;
}
// identifier `<` identifier `>` non-identifier
return noType;
}
// identifier `<` identifier `>` non-identifier
return noType;
}
}
// TODO(danrubel): Consider adding a const for
Expand Down Expand Up @@ -268,21 +255,7 @@ TypeInfo computeType(final Token token, bool required,
.computeIdentifierGFT(required);
}

if (optional('?', next)) {
if (required) {
// identifier `?`
return simpleNullableType;
} else {
next = next.next;
if (isGeneralizedFunctionType(next)) {
// identifier `?` Function `(`
return simpleNullableType;
} else if (looksLikeName(next)) {
// identifier `?` identifier `=`
return simpleNullableType;
}
}
} else if (required || looksLikeName(next)) {
if (required || looksLikeName(next)) {
// identifier identifier
return simpleType;
}
Expand Down
124 changes: 14 additions & 110 deletions pkg/front_end/lib/src/fasta/parser/type_info_impl.dart
View file
Original file line number Diff line number Diff line change
Expand Up @@ -38,10 +38,6 @@ import 'util.dart'
/// when there is a single identifier as the type reference.
const TypeInfo simpleType = const SimpleType();

/// [SimpleNullableType] is a specialized [TypeInfo] returned by [computeType]
/// when there is a single identifier followed by `?` as the type reference.
const TypeInfo simpleNullableType = const SimpleNullableType();

/// [PrefixedType] is a specialized [TypeInfo] returned by [computeType]
/// when the type reference is of the form: identifier `.` identifier.
const TypeInfo prefixedType = const PrefixedType();
Expand All @@ -64,12 +60,6 @@ const TypeInfo simpleTypeWith1ArgumentGtEq =
const TypeInfo simpleTypeWith1ArgumentGtGt =
const SimpleTypeWith1Argument(simpleTypeArgument1GtGt);

/// [SimpleNullableTypeWith1Argument] is a specialized [TypeInfo] returned by
/// [computeType] when the type reference is of the form:
/// identifier `<` identifier `>` `?`.
const TypeInfo simpleNullableTypeWith1Argument =
const SimpleNullableTypeWith1Argument();

/// [SimpleTypeArgument1] is a specialized [TypeParamOrArgInfo] returned by
/// [computeTypeParamOrArg] when the type reference is of the form:
/// `<` identifier `>`.
Expand All @@ -92,10 +82,10 @@ class NoType implements TypeInfo {
const NoType();

@override
TypeInfo get asNonNullable => this;
bool get couldBeExpression => false;

@override
bool get couldBeExpression => false;
TypeInfo asNonNullableType() => this;

@override
Token ensureTypeNotVoid(Token token, Parser parser) {
Expand All @@ -109,9 +99,6 @@ class NoType implements TypeInfo {
Token ensureTypeOrVoid(Token token, Parser parser) =>
ensureTypeNotVoid(token, parser);

@override
bool isConditionalExpressionStart(Token token, Parser parser) => false;

@override
Token parseTypeNotVoid(Token token, Parser parser) =>
parseType(token, parser);
Expand All @@ -133,10 +120,10 @@ class PrefixedType implements TypeInfo {
const PrefixedType();

@override
TypeInfo get asNonNullable => this;
bool get couldBeExpression => true;

@override
bool get couldBeExpression => true;
TypeInfo asNonNullableType() => this;

@override
Token ensureTypeNotVoid(Token token, Parser parser) =>
Expand All @@ -146,9 +133,6 @@ class PrefixedType implements TypeInfo {
Token ensureTypeOrVoid(Token token, Parser parser) =>
parseType(token, parser);

@override
bool isConditionalExpressionStart(Token token, Parser parser) => false;

@override
Token parseTypeNotVoid(Token token, Parser parser) =>
parseType(token, parser);
Expand Down Expand Up @@ -180,44 +164,17 @@ class PrefixedType implements TypeInfo {
}
}

/// See documentation on the [simpleNullableTypeWith1Argument] const.
class SimpleNullableTypeWith1Argument extends SimpleTypeWith1Argument {
const SimpleNullableTypeWith1Argument() : super(simpleTypeArgument1);

@override
TypeInfo get asNonNullable => simpleTypeWith1Argument;

@override
bool isConditionalExpressionStart(Token token, Parser parser) =>
isConditionalThenExpression(skipType(token), parser);

@override
Token parseTypeRest(Token start, Token token, Parser parser) {
token = token.next;
assert(optional('?', token));
parser.listener.handleType(start, token);
return token;
}

@override
Token skipType(Token token) {
token = super.skipType(token).next;
assert(optional('?', token));
return token;
}
}

/// See documentation on the [simpleTypeWith1Argument] const.
class SimpleTypeWith1Argument implements TypeInfo {
final TypeParamOrArgInfo typeArg;

const SimpleTypeWith1Argument(this.typeArg);

@override
TypeInfo get asNonNullable => this;
bool get couldBeExpression => false;

@override
bool get couldBeExpression => false;
TypeInfo asNonNullableType() => this;

@override
Token ensureTypeNotVoid(Token token, Parser parser) =>
Expand All @@ -227,9 +184,6 @@ class SimpleTypeWith1Argument implements TypeInfo {
Token ensureTypeOrVoid(Token token, Parser parser) =>
parseType(token, parser);

@override
bool isConditionalExpressionStart(Token token, Parser parser) => false;

@override
Token parseTypeNotVoid(Token token, Parser parser) =>
parseType(token, parser);
Expand All @@ -256,40 +210,15 @@ class SimpleTypeWith1Argument implements TypeInfo {
}
}

/// See documentation on the [simpleNullableType] const.
class SimpleNullableType extends SimpleType {
const SimpleNullableType();

@override
TypeInfo get asNonNullable => simpleType;

@override
bool isConditionalExpressionStart(Token token, Parser parser) =>
isConditionalThenExpression(skipType(token), parser);

@override
Token parseTypeRest(Token start, Parser parser) {
Token token = start.next;
assert(optional('?', token));
parser.listener.handleType(start, token);
return token;
}

@override
Token skipType(Token token) {
return token.next.next;
}
}

/// See documentation on the [simpleType] const.
class SimpleType implements TypeInfo {
const SimpleType();

@override
TypeInfo get asNonNullable => this;
bool get couldBeExpression => true;

@override
bool get couldBeExpression => true;
TypeInfo asNonNullableType() => this;

@override
Token ensureTypeNotVoid(Token token, Parser parser) =>
Expand All @@ -299,9 +228,6 @@ class SimpleType implements TypeInfo {
Token ensureTypeOrVoid(Token token, Parser parser) =>
parseType(token, parser);

@override
bool isConditionalExpressionStart(Token token, Parser parser) => false;

@override
Token parseTypeNotVoid(Token token, Parser parser) =>
parseType(token, parser);
Expand Down Expand Up @@ -331,10 +257,10 @@ class VoidType implements TypeInfo {
const VoidType();

@override
TypeInfo get asNonNullable => this;
bool get couldBeExpression => false;

@override
bool get couldBeExpression => false;
TypeInfo asNonNullableType() => this;

@override
Token ensureTypeNotVoid(Token token, Parser parser) {
Expand All @@ -347,9 +273,6 @@ class VoidType implements TypeInfo {
Token ensureTypeOrVoid(Token token, Parser parser) =>
parseType(token, parser);

@override
bool isConditionalExpressionStart(Token token, Parser parser) => false;

@override
Token parseTypeNotVoid(Token token, Parser parser) =>
ensureTypeNotVoid(token, parser);
Expand Down Expand Up @@ -414,12 +337,12 @@ class ComplexTypeInfo implements TypeInfo {
: this.start = beforeStart.next;

@override
TypeInfo get asNonNullable {
return this;
}
bool get couldBeExpression => false;

@override
bool get couldBeExpression => false;
TypeInfo asNonNullableType() {
return this;
}

@override
Token ensureTypeNotVoid(Token token, Parser parser) =>
Expand All @@ -429,12 +352,6 @@ class ComplexTypeInfo implements TypeInfo {
Token ensureTypeOrVoid(Token token, Parser parser) =>
parseType(token, parser);

@override
bool isConditionalExpressionStart(Token token, Parser parser) {
//return isConditionalThenExpression(token.next.next, parser);
return false;
}

@override
Token parseTypeNotVoid(Token token, Parser parser) =>
parseType(token, parser);
Expand Down Expand Up @@ -1144,16 +1061,3 @@ Token splitCloser(Token closer) {
}
return null;
}

/// Return `true` if the tokens after [token]
/// represent a valid expression followed by a `:`.
bool isConditionalThenExpression(Token token, Parser parser) {
// TODO(danrubel): Consider adding checks for simple situations
// before resorting to heavy weight lookahead.

final originalListener = parser.listener;
parser.listener = new ForwardingListener();
token = parser.parseExpression(token);
parser.listener = originalListener;
return optional(':', token.next);
}
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