mirror of
https://github.com/carbon-language/carbon-lang.git
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[executable semantics] Use type-safe variant in C++ parser (#364)
We're now one step away from eliminating bare pointers in semantic actions. There are plenty of other cleanups and modernizations that can be made in the parser, but the elimination of bare pointers is the one that has the highest impact for the codebase.
This commit is contained in:
Dave Abrahams
GitHub
@@ -9,9 +9,16 @@
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%require "3.2"
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%language "c++"
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// We don't need a separate header for Bison locations yet.
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// We don't need a separate header for Bison locations.
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%define api.location.file none
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// Use a type-safe C++ variant for semantic values
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%define api.value.type variant
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// Have Bison generate the functions ‘make_TEXT’ and ‘make_NUMBER’, but also
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// ‘make_YYEOF’, for the end of input.
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%define api.token.constructor
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//
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// Parameters to the parser and lexer
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//
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@@ -64,8 +71,6 @@ void yy::parser::error(
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}
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%define api.value.type union
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%token <int> integer_literal
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%token <char*> identifier
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%type <char*> designator
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@@ -89,6 +94,7 @@ void yy::parser::error(
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%type <std::list<std::pair<std::string, Carbon::Expression*>>*> alternative_list
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%type <std::pair<Carbon::Expression*, Carbon::Statement*>*> clause
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%type <std::list<std::pair<Carbon::Expression*, Carbon::Statement*>>*> clause_list
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%token END_OF_FILE 0
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%token AND
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%token OR
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%token NOT
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@@ -99,7 +105,7 @@ void yy::parser::error(
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%token FNTY
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%token ARROW
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%token VAR
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%token EQUAL
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%token EQUAL_EQUAL
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%token IF
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%token ELSE
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%token WHILE
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@@ -115,13 +121,31 @@ void yy::parser::error(
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%token DBLARROW
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%token DEFAULT
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%token AUTO
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%nonassoc '{' '}'
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%nonassoc ':' ',' DBLARROW
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%token
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EQUAL "="
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MINUS "-"
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PLUS "+"
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STAR "*"
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SLASH "/"
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LEFT_PARENTHESIS "("
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RIGHT_PARENTHESIS ")"
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LEFT_CURLY_BRACE "{"
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RIGHT_CURLY_BRACE "}"
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LEFT_SQUARE_BRACKET "["
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RIGHT_SQUARE_BRACKET "]"
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PERIOD "."
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COMMA ","
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SEMICOLON ";"
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COLON ":"
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;
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%nonassoc "{" "}"
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%nonassoc ":" "," DBLARROW
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%left OR AND
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%nonassoc EQUAL NOT
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%left '+' '-'
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%left '.' ARROW
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%nonassoc '(' ')' '[' ']'
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%nonassoc EQUAL_EQUAL NOT
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%left "+" "-"
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%left "." ARROW
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%nonassoc "(" ")" "[" "]"
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%start input
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%locations
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%%
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@@ -137,9 +161,9 @@ expression:
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{ $$ = Carbon::MakeVar(yylineno, $1); }
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| expression designator
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{ $$ = Carbon::MakeGetField(yylineno, $1, $2); }
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| expression '[' expression ']'
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| expression "[" expression "]"
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{ $$ = Carbon::MakeIndex(yylineno, $1, $3); }
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| expression ':' identifier
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| expression ":" identifier
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{ $$ = Carbon::MakeVarPat(yylineno, $3, $1); }
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| integer_literal
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{ $$ = Carbon::MakeInt(yylineno, $1); }
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@@ -156,11 +180,11 @@ expression:
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| AUTO
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{ $$ = Carbon::MakeAutoType(yylineno); }
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| paren_expression { $$ = $1; }
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| expression EQUAL expression
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| expression EQUAL_EQUAL expression
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{ $$ = Carbon::MakeBinOp(yylineno, Carbon::Operator::Eq, $1, $3); }
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| expression '+' expression
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| expression "+" expression
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{ $$ = Carbon::MakeBinOp(yylineno, Carbon::Operator::Add, $1, $3); }
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| expression '-' expression
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| expression "-" expression
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{ $$ = Carbon::MakeBinOp(yylineno, Carbon::Operator::Sub, $1, $3); }
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| expression AND expression
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{ $$ = Carbon::MakeBinOp(yylineno, Carbon::Operator::And, $1, $3); }
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@@ -168,16 +192,16 @@ expression:
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{ $$ = Carbon::MakeBinOp(yylineno, Carbon::Operator::Or, $1, $3); }
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| NOT expression
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{ $$ = Carbon::MakeUnOp(yylineno, Carbon::Operator::Not, $2); }
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| '-' expression
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| "-" expression
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{ $$ = Carbon::MakeUnOp(yylineno, Carbon::Operator::Neg, $2); }
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| expression tuple
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{ $$ = Carbon::MakeCall(yylineno, $1, $2); }
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| FNTY tuple return_type
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{ $$ = Carbon::MakeFunType(yylineno, $2, $3); }
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;
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designator: '.' identifier { $$ = $2; }
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designator: "." identifier { $$ = $2; }
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;
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paren_expression: '(' field_list ')'
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paren_expression: "(" field_list ")"
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{
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if ($2->fields->size() == 1 &&
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$2->fields->front().first == "" &&
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@@ -190,7 +214,7 @@ paren_expression: '(' field_list ')'
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}
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}
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;
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tuple: '(' field_list ')'
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tuple: "(" field_list ")"
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{
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auto vec = new std::vector<std::pair<std::string,Carbon::Expression*>>(
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$2->fields->begin(), $2->fields->end());
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@@ -204,7 +228,7 @@ field:
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fields->push_back(std::make_pair("", $1));
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$$ = Carbon::MakeFieldList(fields);
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}
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| designator '=' pattern
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| designator "=" pattern
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{
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auto fields =
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new std::list<std::pair<std::string, Carbon::Expression*>>();
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@@ -220,7 +244,7 @@ field_list:
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}
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| field
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{ $$ = $1; }
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| field ',' field_list
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| field "," field_list
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{ $$ = Carbon::MakeConsField($1, $3); }
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;
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clause:
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@@ -242,25 +266,25 @@ clause_list:
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{ $$ = $2; $$->push_front(*$1); }
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;
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statement:
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expression '=' expression ';'
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expression "=" expression ";"
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{ $$ = Carbon::MakeAssign(yylineno, $1, $3); }
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| VAR pattern '=' expression ';'
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| VAR pattern "=" expression ";"
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{ $$ = Carbon::MakeVarDef(yylineno, $2, $4); }
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| expression ';'
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| expression ";"
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{ $$ = Carbon::MakeExpStmt(yylineno, $1); }
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| IF '(' expression ')' statement optional_else
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| IF "(" expression ")" statement optional_else
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{ $$ = Carbon::MakeIf(yylineno, $3, $5, $6); }
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| WHILE '(' expression ')' statement
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| WHILE "(" expression ")" statement
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{ $$ = Carbon::MakeWhile(yylineno, $3, $5); }
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| BREAK ';'
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| BREAK ";"
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{ $$ = Carbon::MakeBreak(yylineno); }
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| CONTINUE ';'
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| CONTINUE ";"
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{ $$ = Carbon::MakeContinue(yylineno); }
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| RETURN expression ';'
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| RETURN expression ";"
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{ $$ = Carbon::MakeReturn(yylineno, $2); }
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| '{' statement_list '}'
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| "{" statement_list "}"
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{ $$ = Carbon::MakeBlock(yylineno, $2); }
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| MATCH '(' expression ')' '{' clause_list '}'
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| MATCH "(" expression ")" "{" clause_list "}"
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{ $$ = Carbon::MakeMatch(yylineno, $3, $6); }
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;
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optional_else:
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@@ -285,20 +309,20 @@ return_type:
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{ $$ = $2; }
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;
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function_definition:
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FN identifier tuple return_type '{' statement_list '}'
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FN identifier tuple return_type "{" statement_list "}"
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{ $$ = MakeFunDef(yylineno, $2, $4, $3, $6); }
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| FN identifier tuple DBLARROW expression ';'
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| FN identifier tuple DBLARROW expression ";"
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{
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$$ = Carbon::MakeFunDef(yylineno, $2, Carbon::MakeAutoType(yylineno), $3,
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Carbon::MakeReturn(yylineno, $5));
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}
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;
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function_declaration:
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FN identifier tuple return_type ';'
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FN identifier tuple return_type ";"
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{ $$ = MakeFunDef(yylineno, $2, $4, $3, 0); }
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;
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member:
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VAR expression ':' identifier ';'
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VAR expression ":" identifier ";"
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{ $$ = MakeField(yylineno, $4, $2); }
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;
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member_list:
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@@ -326,7 +350,7 @@ alternative_list:
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$$ = new std::list<std::pair<std::string, Carbon::Expression*>>();
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$$->push_front(*$1);
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}
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| alternative ',' alternative_list
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| alternative "," alternative_list
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{ $$ = $3; $$->push_front(*$1); }
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;
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declaration:
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@@ -334,12 +358,12 @@ declaration:
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{ $$ = new Carbon::Declaration(Carbon::FunctionDeclaration{$1}); }
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| function_declaration
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{ $$ = new Carbon::Declaration(Carbon::FunctionDeclaration{$1}); }
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| STRUCT identifier '{' member_list '}'
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| STRUCT identifier "{" member_list "}"
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{
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$$ = new Carbon::Declaration(
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Carbon::StructDeclaration{yylineno, $2, $4});
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}
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| CHOICE identifier '{' alternative_list '}'
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| CHOICE identifier "{" alternative_list "}"
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{
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$$ = new Carbon::Declaration(
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Carbon::ChoiceDeclaration{yylineno, $2, std::list(*$4)});
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