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Deconstruction-declaration parsing for local declaration, for and foreach #12104

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Jun 24, 2016
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Deconstruction-declaration parsing for local declaration, for and foreach #12104

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62d0b88
Deconstruction-declaration parsing for local declaration, for and
jcouv Jun 13, 2016
219bc7c
Switching to new syntax model
jcouv Jun 21, 2016
1160bc7
Minor improvements
jcouv Jun 21, 2016
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Improving comments
jcouv Jun 21, 2016
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jcouv Jun 21, 2016
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jcouv Jun 21, 2016
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jcouv Jun 22, 2016
22306b3
Fixing public API
jcouv Jun 23, 2016
db860b6
Fixing one unittest
jcouv Jun 23, 2016
e96585a
PR feedback (4)
jcouv Jun 23, 2016
9ae475a
Refining public API
jcouv Jun 23, 2016
de691fe
Removing accidentally-added files
jcouv Jun 24, 2016
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jcouv Jun 24, 2016
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66 changes: 34 additions & 32 deletions docs/features/deconstruction.md
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Original file line number Diff line number Diff line change
Expand Up @@ -121,61 +121,63 @@ Note that tuples (`System.ValueTuple`) don't need to invoke Deconstruct.
declaration_statement
: local_variable_declaration ';'
| local_constant_declaration ';'
| local_variable_combo_declaration ';' // new
;

local_variable_combo_declaration
: local_variable_combo_declaration_lhs '=' expression
local_variable_declaration
: local_variable_type local_variable_declarators
| deconstruction_declaration // new
;

local_variable_combo_declaration_lhs
: 'var' '(' identifier_list ')'
| '(' local_variable_list ')'
;
deconstruction_declaration // new
: deconstruction_variables '=' expression
;

identifier_list
: identifier ',' identifier
| identifier_list ',' identifier
;
deconstuction_variables
: '(' deconstuction_variables_nested (',' deconstuction_variables_nested)* ')'
| 'var' deconstruction_identifiers
;

local_variable_list
: local_variable_type identifier ',' local_variable_type identifier
| local_variable_list ',' local_variable_type identifier
;
deconstuction_variables_nested // new
: deconstuction_variables
| type identifier
;

deconstruction_identifiers
: '(' deconstruction_identifiers_nested (',' deconstruction_identifiers_nested)* ')'
;

deconstruction_identifiers_nested // new
: deconstruction_identifiers
| identifier
;

foreach_statement
: 'foreach' '(' local_variable_type identifier 'in' expression ')' embedded_statement
| 'foreach' '(' local_variable_combo_declaration_lhs 'in' expression ')' embedded_statement // new
| 'foreach' '(' deconstruction_variables 'in' expression ')' embedded_statement // new
;

for_statement
: 'for' '(' for_initializer? ';' for_condition? ';' for_iterator? ')' embedded_statement
;
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Has for_statement changed or is the same as without deconstruction variables?

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In the grammar, I kept for_statement as before. The difference appears below, in for_initializer.


for_initializer
: local_variable_declaration
| local_variable_combo_declaration // new
| deconstruction_declaration // new
| statement_expression_list
;

let_clause
: 'let' identifier '=' expression
| 'let' '(' identifier_list ')' '=' expression // new
| 'let' deconstruction_identifiers '=' expression // new
;

from_clause // not sure
from_clause
: 'from' type? identifier 'in' expression
;

join_clause // not sure
: 'join' type? identifier 'in' expression 'on' expression 'equals' expression
;

join_into_clause // not sure
: 'join' type? identifier 'in' expression 'on' expression 'equals' expression 'into' identifier
;

constant_declarator // not sure
: identifier '=' constant_expression
| 'from' deconstuction_variables 'in' expression // new
| 'from' deconstruction_identifiers 'in' expression // new
;
```

Treat deconstruction of a tuple into new variables as a new kind of node (not AssignmentExpression).
It would pick up the behavior of each contexts where new variables can be declared (TODO: need to list). For instance, in LINQ, new variables go into a transparent identifiers.
It is seen as deconstructing into separate variables (we don't introduce transparent identifiers in contexts where they didn't exist previously).

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9 changes: 9 additions & 0 deletions src/Compilers/CSharp/Portable/CSharpResources.Designer.cs
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3 changes: 3 additions & 0 deletions src/Compilers/CSharp/Portable/CSharpResources.resx
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Original file line number Diff line number Diff line change
Expand Up @@ -4896,4 +4896,7 @@ To remove the warning, you can use /reference instead (set the Embed Interop Typ
<data name="ERR_CannotDeconstructDynamic" xml:space="preserve">
<value>Cannot deconstruct dynamic objects.</value>
</data>
<data name="ERR_DeconstructTooFewElements" xml:space="preserve">
<value>Deconstruction must contain at least two variables.</value>
</data>
</root>
1 change: 1 addition & 0 deletions src/Compilers/CSharp/Portable/Errors/ErrorCode.cs
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Expand Up @@ -1398,5 +1398,6 @@ internal enum ErrorCode
ERR_DeconstructRequiresExpression = 8210,
ERR_DeconstructWrongCardinality = 8211,
ERR_CannotDeconstructDynamic = 8212,
ERR_DeconstructTooFewElements = 8213,
}
}
1 change: 1 addition & 0 deletions src/Compilers/CSharp/Portable/GlobalSuppressions.cs
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Expand Up @@ -10,4 +10,5 @@
[assembly: System.Diagnostics.CodeAnalysis.SuppressMessage("ApiDesign", "RS0027:Public API with optional parameter(s) should have the most parameters amongst its public overloads.", Justification = "<Pending>", Scope = "member", Target = "~M:Microsoft.CodeAnalysis.CSharp.SyntaxFactory.WhenClause(Microsoft.CodeAnalysis.CSharp.Syntax.ExpressionSyntax)~Microsoft.CodeAnalysis.CSharp.Syntax.WhenClauseSyntax")]
[assembly: System.Diagnostics.CodeAnalysis.SuppressMessage("ApiDesign", "RS0027:Public API with optional parameter(s) should have the most parameters amongst its public overloads.", Justification = "<Pending>", Scope = "member", Target = "~M:Microsoft.CodeAnalysis.CSharp.SyntaxFactory.IncompleteMember(Microsoft.CodeAnalysis.CSharp.Syntax.TypeSyntax)~Microsoft.CodeAnalysis.CSharp.Syntax.IncompleteMemberSyntax")]
[assembly: System.Diagnostics.CodeAnalysis.SuppressMessage("ApiDesign", "RS0027:Public API with optional parameter(s) should have the most parameters amongst its public overloads.", Justification = "<Pending>", Scope = "member", Target = "~M:Microsoft.CodeAnalysis.CSharp.SyntaxFactory.ReturnStatement(Microsoft.CodeAnalysis.CSharp.Syntax.ExpressionSyntax)~Microsoft.CodeAnalysis.CSharp.Syntax.ReturnStatementSyntax")]
[assembly: System.Diagnostics.CodeAnalysis.SuppressMessage("ApiDesign", "RS0027:Public API with optional parameter(s) should have the most parameters amongst its public overloads.", Justification = "<Pending>", Scope = "member", Target = "~M:Microsoft.CodeAnalysis.CSharp.SyntaxFactory.DeconstructionVariablesVar(Microsoft.CodeAnalysis.CSharp.Syntax.TupleExpressionSyntax)~Microsoft.CodeAnalysis.CSharp.Syntax.DeconstructionVariablesVarSyntax")]

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