Class: Ikra::TypeInference::SymbolTable

Inherits:
Object
  • Object
show all
Defined in:
lib/types/inference/symbol_table.rb

Overview

This is a symbol table that stores type information about variables. Ruby has a “flat” variable scope in method, i.e., variables defined in loop bodies, if statement bodies, or begin nodes are also visible outside of them.

Every method/block has its own symbol table.

Defined Under Namespace

Classes: Variable

Instance Attribute Summary collapse

Instance Method Summary collapse

Constructor Details

#initialize ⇒ SymbolTable

Returns a new instance of SymbolTable.



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# File 'lib/types/inference/symbol_table.rb', line 36

def initialize
    # This is a mapping from variable names to Variable instances.
    @symbols = {}
    @return_type = Types::UnionType.new
end

Instance Attribute Details

#return_type ⇒ Object (readonly)

Returns the value of attribute return_type.



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# File 'lib/types/inference/symbol_table.rb', line 31

def return_type
  @return_type
end

#symbols ⇒ Object (readonly)

For debug purposes



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# File 'lib/types/inference/symbol_table.rb', line 34

def symbols
  @symbols
end

Instance Method Details

#[](variable_name) ⇒ Object 



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# File 'lib/types/inference/symbol_table.rb', line 46

def [](variable_name)
    if !has_variable?(variable_name)
        raise AssertionError.new("Variable #{variable_name} not defined")
    end

    return @symbols[variable_name].type
end

#clear! ⇒ Object 



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# File 'lib/types/inference/symbol_table.rb', line 42

def clear!
    @symbols = {}
end

#declare_variable(variable_name, type: Types::UnionType.new, kind: :local) ⇒ Object

Declares a local variable and overwrites (shadows) existing variables (lexical variables). Use this method for method/block parameters.



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# File 'lib/types/inference/symbol_table.rb', line 119

def declare_variable(variable_name, type: Types::UnionType.new, kind: :local)
    @symbols[variable_name] = Variable.new(type: Types::UnionType.new, kind: kind)
    expand_type(variable_name, type)
end

#ensure_variable_declared(variable_name, type: Types::UnionType.new, kind: :local) ⇒ Object

Declares a local variable. This method should be used only for regular local variables (not parameters). Does not shadow lexical variables.



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# File 'lib/types/inference/symbol_table.rb', line 108

def ensure_variable_declared(variable_name, type: Types::UnionType.new, kind: :local)
    if !has_variable?(variable_name)
        declare_variable(variable_name, type: type, kind: kind)
    else
        # Extend type of variable
        expand_type(variable_name, type)
    end
end

#expand_return_type(type) ⇒ Object 



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# File 'lib/types/inference/symbol_table.rb', line 98

def expand_return_type(type)
    @return_type.expand(type)
end

#expand_type(variable_name, type) ⇒ Object 



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# File 'lib/types/inference/symbol_table.rb', line 88

def expand_type(variable_name, type)
    if !has_variable?(variable_name)
        raise AssertionError.new(
            "Attempt to expand type of variable #{variable_name} but not found in " +
            " symbol table")
    end

    @symbols[variable_name].type.expand(type)
end

#read!(variable_name) ⇒ Object 



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# File 'lib/types/inference/symbol_table.rb', line 54

def read!(variable_name)
    if !has_variable?(variable_name)
        raise AssertionError.new(
            "Variable #{variable_name} read but not found in symbol table")
    end

    @symbols[variable_name].read = true
end

#read_and_written_variables ⇒ Object 



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# File 'lib/types/inference/symbol_table.rb', line 84

def read_and_written_variables
    return read_variables + written_variables
end

#read_variables ⇒ Object 



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# File 'lib/types/inference/symbol_table.rb', line 72

def read_variables
    return @symbols.select do |k, v|
        v.read
    end.keys
end

#written!(variable_name) ⇒ Object 



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# File 'lib/types/inference/symbol_table.rb', line 63

def written!(variable_name)
    if !has_variable?(variable_name)
        raise AssertionError.new(
            "Variable #{variable_name} written but not found in symbol table")
    end

    @symbols[variable_name].written = true
end

#written_variables ⇒ Object 



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# File 'lib/types/inference/symbol_table.rb', line 78

def written_variables
    return @symbols.select do |k, v|
        v.written
    end.keys
end