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JustAnotherJAPL/src/backend/compiler.nim

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# Copyright 2021 Mattia Giambirtone & All Contributors
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
# http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.
import meta/token
import meta/ast
import meta/errors
import meta/bytecode
import ../config
import ../util/multibyte
import strformat
import algorithm
import parseutils
import sequtils
export ast
export bytecode
export token
export multibyte
type
Name = ref object of RootObj
## A compile-time wrapper around names.
## Depth indicates to which scope
## the variable belongs, zero meaning
## the global one. Note that all names
## are resolved statically unless the
## dynamic specifier is used, hence if
## the compiler cannot resolve a name
## at compile-time it will error out even
## if everything would be fine at runtime
name: IdentExpr
owner: string
depth: int
isPrivate: bool
StaticName = ref object of Name
## A wrapper around statically bound names.
isConst: bool
Compiler* = ref object
## A wrapper around the compiler's state
chunk: Chunk
ast: seq[ASTNode]
enclosing: Compiler
current: int
file: string
names: seq[Name]
# This differentiation is needed for a few things, namely:
# - To forbid assignment to constants
# - To error out on name resolution for a never-declared variable (static or dynamic)
# - To correctly predict where locals will be on the stack at runtime
staticNames: seq[StaticName]
scopeDepth: int
currentFunction: FunDecl
proc initCompiler*(): Compiler =
## Initializes a new Compiler object
new(result)
result.ast = @[]
result.current = 0
result.file = ""
result.names = @[]
result.staticNames = @[]
result.scopeDepth = 0
result.currentFunction = nil
## Forward declarations
proc expression(self: Compiler, node: ASTNode)
proc statement(self: Compiler, node: ASTNode)
proc declaration(self: Compiler, node: ASTNode)
proc peek(self: Compiler, distance: int = 0): ASTNode
## End of forward declarations
## Utility functions
proc error(self: Compiler, message: string) =
## Raises a formatted CompileError exception
let tok = self.peek().token
raise newException(CompileError, &"A fatal error occurred while compiling '{self.file}', line {tok.line} at '{tok.lexeme}' -> {message}")
proc peek(self: Compiler, distance: int = 0): ASTNode =
## Peeks at the AST node at the given distance.
## If the distance is out of bounds, the last
## AST node in the tree is returned. A negative
## distance may be used to retrieve previously
## consumed AST nodes
if self.ast.high() == -1 or self.current + distance > self.ast.high() or self.current + distance < 0:
result = self.ast[^1]
else:
result = self.ast[self.current + distance]
proc done(self: Compiler): bool =
## Returns true if the compiler is done
## compiling, false otherwise
result = self.current > self.ast.high()
proc check(self: Compiler, kind: NodeKind): bool =
## Returns if the current node is of the
## expected kind
if self.done():
return false
return self.peek().kind == kind
proc step(self: Compiler): ASTNode =
## Steps to the next node and returns
## the consumed one
result = self.peek()
if not self.done():
self.current += 1
proc match(self: Compiler, kind: NodeKind): bool =
## Same as self.check(), but it calls self.step()
## internally if self.check() returns true
if self.check(kind):
discard self.step()
return true
return false
proc expect(self: Compiler, kind: NodeKind, message: string): ASTNode =
## Same as self.match(), but returns the consumed
## AST node instead of a boolean and errors out
## with the given error message if the token
## doesn't match
if self.match(kind):
result = self.peek(-1)
else:
self.error(message)
proc emitByte(self: Compiler, byt: OpCode|uint8) =
## Emits a single byte, writing it to
## the current chunk being compiled
when DEBUG_TRACE_COMPILER:
echo &"DEBUG - Compiler: Emitting {$byt}"
self.chunk.write(uint8 byt, self.peek().token.line)
proc emitBytes(self: Compiler, byt1: OpCode|uint8, byt2: OpCode|uint8) =
## Emits multiple bytes instead of a single one, this is useful
## to emit operators along with their operands or for multi-byte
## instructions that are longer than one byte
self.emitByte(uint8 byt1)
self.emitByte(uint8 byt2)
proc emitBytes(self: Compiler, bytarr: array[3, uint8]) =
## Handy helper method to write an array of 3 bytes into
## the current chunk, calling emitByte on each of its
## elements
self.emitBytes(bytarr[0], bytarr[1])
self.emitByte(bytarr[2])
proc makeConstant(self: Compiler, val: ASTNode): array[3, uint8] =
## Adds a constant to the current chunk's constant table
## and returns its index as a 3-byte array of uint8s
result = self.chunk.addConstant(val)
proc emitConstant(self: Compiler, obj: ASTNode) =
## Emits a LoadConstant instruction along
## with its operand
self.emitByte(LoadConstant)
self.emitBytes(self.makeConstant(obj))
proc identifierConstant(self: Compiler, identifier: IdentExpr): array[3, uint8] =
## Emits an identifier name as a string in the current chunk's constant
## table. This is used to load globals declared as dynamic that cannot
## be resolved statically by the compiler
try:
result = self.makeConstant(identifier)
except CompileError:
self.error(getCurrentExceptionMsg())
## End of utility functions
proc literal(self: Compiler, node: ASTNode) =
## Emits instructions for literals such
## as singletons, strings, numbers and
## collections
case node.kind:
of trueExpr:
self.emitByte(OpCode.True)
of falseExpr:
self.emitByte(OpCode.False)
of nilExpr:
self.emitByte(OpCode.Nil)
of infExpr:
self.emitByte(OpCode.Inf)
of nanExpr:
self.emitByte(OpCode.Nan)
of strExpr:
self.emitConstant(node)
# The optimizer will emit warning
# for overflowing numbers. Here, we
# treat them as errors
of intExpr:
var x: int
var y = IntExpr(node)
try:
assert parseInt(y.literal.lexeme, x) == len(y.literal.lexeme)
except ValueError:
self.error("integer value out of range")
self.emitConstant(y)
# Even though most likely the optimizer
# will collapse all these other literals
# to nodes of kind intExpr, that can be
# disabled. This also allows us to catch
# basic overflow errors before running any code
of hexExpr:
var x: int
var y = HexExpr(node)
try:
assert parseHex(y.literal.lexeme, x) == len(y.literal.lexeme)
except ValueError:
self.error("integer value out of range")
self.emitConstant(newIntExpr(Token(lexeme: $x, line: y.token.line, pos: (start: y.token.pos.start, stop: y.token.pos.start + len($x)))))
of binExpr:
var x: int
var y = BinExpr(node)
try:
assert parseBin(y.literal.lexeme, x) == len(y.literal.lexeme)
except ValueError:
self.error("integer value out of range")
self.emitConstant(newIntExpr(Token(lexeme: $x, line: y.token.line, pos: (start: y.token.pos.start, stop: y.token.pos.start + len($x)))))
of octExpr:
var x: int
var y = OctExpr(node)
try:
assert parseOct(y.literal.lexeme, x) == len(y.literal.lexeme)
except ValueError:
self.error("integer value out of range")
self.emitConstant(newIntExpr(Token(lexeme: $x, line: y.token.line, pos: (start: y.token.pos.start, stop: y.token.pos.start + len($x)))))
of floatExpr:
var x: float
var y = FloatExpr(node)
try:
assert parseFloat(y.literal.lexeme, x) == len(y.literal.lexeme)
except ValueError:
self.error("floating point value out of range")
self.emitConstant(y)
of listExpr:
var y = ListExpr(node)
for member in y.members:
self.expression(member)
self.emitByte(BuildList)
self.emitBytes(y.members.len().toTriple()) # 24-bit integer, meaning list literals can have up to 2^24 elements
of tupleExpr:
var y = TupleExpr(node)
for member in y.members:
self.expression(member)
self.emitByte(BuildTuple)
self.emitBytes(y.members.len().toTriple())
of setExpr:
var y = SetExpr(node)
for member in y.members:
self.expression(member)
self.emitByte(BuildSet)
self.emitBytes(y.members.len().toTriple())
of dictExpr:
var y = DictExpr(node)
for (key, value) in zip(y.keys, y.values):
self.expression(key)
self.expression(value)
self.emitByte(BuildDict)
self.emitBytes(y.keys.len().toTriple())
else:
self.error(&"invalid AST node of kind {node.kind} at literal(): {node} (This is an internal error and most likely a bug)")
proc unary(self: Compiler, node: UnaryExpr) =
## Compiles unary expressions such as negation or
## bitwise inversion
self.expression(node.a) # Pushes the operand onto the stack
case node.operator.kind:
of Minus:
self.emitByte(UnaryNegate)
of Plus:
discard # Unary + does nothing
of TokenType.LogicalNot:
self.emitByte(OpCode.LogicalNot)
of Tilde:
self.emitByte(UnaryNot)
else:
self.error(&"invalid AST node of kind {node.kind} at unary(): {node} (This is an internal error and most likely a bug)")
proc binary(self: Compiler, node: BinaryExpr) =
## Compiles all binary expressions
# These two lines prepare the stack by pushing the
# opcode's operands onto it
self.expression(node.a)
self.expression(node.b)
case node.operator.kind:
of Plus:
self.emitByte(BinaryAdd)
of Minus:
self.emitByte(BinarySubtract)
of Asterisk:
self.emitByte(BinaryMultiply)
of DoubleAsterisk:
self.emitByte(BinaryPow)
of Percentage:
self.emitByte(BinaryMod)
of FloorDiv:
self.emitByte(BinaryFloorDiv)
of Slash:
self.emitByte(BinaryDivide)
of Ampersand:
self.emitByte(BinaryAnd)
of Caret:
self.emitByte(BinaryXor)
of Pipe:
self.emitByte(BinaryOr)
of As:
self.emitByte(BinaryAs)
of Is:
self.emitByte(BinaryIs)
of IsNot:
self.emitByte(BinaryIsNot)
of Of:
self.emitByte(BinaryOf)
of RightShift:
self.emitByte(BinaryShiftRight)
of LeftShift:
self.emitByte(BinaryShiftLeft)
# TODO: In-place operations (requires variables)
else:
self.error(&"invalid AST node of kind {node.kind} at binary(): {node} (This is an internal error and most likely a bug)")
proc declareName(self: Compiler, node: ASTNode) =
## Compiles all name declarations (constants, static,
## and dynamic)
case node.kind:
of varDecl:
var node = VarDecl(node)
if not node.isStatic:
# This emits code for dynamically-resolved variables (i.e. globals declared as dynamic and unresolvable names)
self.emitByte(DeclareName)
self.emitBytes(self.identifierConstant(IdentExpr(node.name)))
self.names.add(Name(depth: self.scopeDepth, name: IdentExpr(node.name),
isPrivate: node.isPrivate, owner: node.owner))
elif node.isConst:
# Constants are emitted as, you guessed it, constant instructions
# no matter the scope depth. Also, name resolution specifiers do not
# apply to them (because what would it mean for a constant to be dynamic
# anyway?)
self.names.add(Name(depth: self.scopeDepth, name: IdentExpr(node.name),
isPrivate: node.isPrivate, owner: node.owner))
self.emitConstant(node.value)
else:
# Statically resolved variable here
if self.staticNames.high() > 16777215:
# If someone ever hits this limit in real-world scenarios, I swear I'll
# slap myself 100 times with a sign saying "I'm dumb". Mark my words
self.error("cannot declare more than 16777215 static variables at a time")
self.staticNames.add(StaticName(depth: self.scopeDepth, name: IdentExpr(node.name),
isPrivate: node.isPrivate, owner: node.owner, isConst: node.isConst))
else:
discard # TODO: Classes, functions
proc varDecl(self: Compiler, node: VarDecl) =
## Compiles variable declarations
self.expression(node.value)
self.declareName(node)
proc resolveDynamic(self: Compiler, name: IdentExpr, depth: int = self.scopeDepth): Name =
## Traverses self.names backwards and returns the
## first name object with the given name at the given
## depth. The default depth is the current one. Returns
## nil when the name can't be found. This helper function
## is only useful when detecting a few errors and edge
## cases
for obj in reversed(self.names):
if obj.name.token.lexeme == name.token.lexeme and obj.depth == depth:
return obj
return nil
proc resolveStatic(self: Compiler, name: IdentExpr, depth: int = self.scopeDepth): StaticName =
## Traverses self.staticNames backwards and returns the
## first name object with the given name at the given
## depth. The default depth is the current one. Returns
## nil when the name can't be found. This helper function
## is only useful when detecting a few errors and edge
## cases
for obj in reversed(self.staticNames):
if obj.name.token.lexeme == name.token.lexeme and obj.depth == depth:
return obj
return nil
proc getStaticIndex(self: Compiler, name: IdentExpr): int =
## Gets the predicted stack position of the given variable
## if it is static, returns -1 if it is to be bound dynamically
var i: int = self.staticNames.high()
for variable in reversed(self.staticNames):
if name.name.lexeme == variable.name.name.lexeme:
return i
dec(i)
return -1
proc identifier(self: Compiler, node: IdentExpr) =
## Compiles access to identifiers
let s = self.resolveStatic(node)
let d = self.resolveDynamic(node)
if s == nil and d == nil and self.scopeDepth == 0:
# Usage of undeclared globals is easy to detect at the top level
self.error(&"reference to undeclared name '{node.name.lexeme}'")
let index = self.getStaticIndex(node)
if index != -1:
self.emitByte(LoadNameFast) # Scoping/static resolution
self.emitBytes(index.toTriple())
else:
self.emitByte(LoadName)
self.emitBytes(self.identifierConstant(node))
proc assignment(self: Compiler, node: ASTNode) =
## Compiles assignment expressions
case node.kind:
of assignExpr:
var node = AssignExpr(node)
var name = IdentExpr(node.name)
let r = self.resolveStatic(name)
if r != nil and r.isConst:
self.error("cannot assign to constant")
# Assignment only encompasses variable assignments
# so we can ensure the name is a constant
self.expression(node.value)
let index = self.getStaticIndex(name)
if index != -1:
self.emitByte(UpdateNameFast)
self.emitBytes(index.toTriple())
else:
self.emitByte(UpdateName)
self.emitBytes(self.makeConstant(name))
of setItemExpr:
var node = SetItemExpr(node)
# TODO
else:
self.error(&"invalid AST node of kind {node.kind} at assignment(): {node} (This is an internal error and most likely a bug)")
proc beginScope(self: Compiler) =
## Begins a new local scope
inc(self.scopeDepth)
proc endScope(self: Compiler) =
## Ends the current local scope
if self.scopeDepth <= 0:
self.error("cannot call endScope with scopeDepth <= 0 (This is an internal error and most likely a bug)")
for ident in reversed(self.staticNames):
if ident.depth > self.scopeDepth:
# All variables with a scope depth larger than the current one
# are now out of scope. Begone, you're now homeless!
self.emitByte(Pop)
discard self.staticNames.pop()
dec(self.scopeDepth)
proc blockStmt(self: Compiler, node: BlockStmt) =
## Compiles block statements, which create a new
## local scope.
self.beginScope()
for decl in node.code:
self.declaration(decl)
self.endScope()
proc expression(self: Compiler, node: ASTNode) =
## Compiles all expressions
case node.kind:
of getItemExpr:
discard
# Note that for setItem and assign we don't convert
# the node to its true type because that type information
# would be lost in the call anyway. The differentiation
# happens in self.assignment
of setItemExpr:
self.assignment(node)
of assignExpr:
self.assignment(node)
of identExpr:
self.identifier(IdentExpr(node))
of unaryExpr:
# Unary expressions such as ~5 and -3
self.unary(UnaryExpr(node))
of groupingExpr:
self.expression(GroupingExpr(node).expression)
of binaryExpr:
# Binary expressions such as 2 ^ 5 and 0.66 * 3.14
self.binary(BinaryExpr(node))
of intExpr, hexExpr, binExpr, octExpr, strExpr, falseExpr, trueExpr, infExpr, nanExpr, floatExpr, nilExpr:
# Fortunately for us, all of these AST nodes types inherit from the base LiteralExpr
# type
self.literal(LiteralExpr(node))
of tupleExpr, setExpr, listExpr:
# Since all of these AST nodes share
# the same structure, and the kind
# discriminant is enough to tell one
# from the other, why bother with
# specialized cases when one is enough?
self.literal(ListExpr(node))
of dictExpr:
self.literal(DictExpr(node))
else:
self.error(&"invalid AST node of kind {node.kind} at expression(): {node} (This is an internal error and most likely a bug)") # TODO
proc statement(self: Compiler, node: ASTNode) =
## Compiles all statements
case node.kind:
of exprStmt:
self.expression(ExprStmt(node).expression)
self.emitByte(Pop) # Expression statements discard their value. Their main use case is side effects in function calls
# TODO
of ifStmt:
discard
of delStmt:
discard
of assertStmt:
discard
of raiseStmt:
discard
of breakStmt:
discard
of continueStmt:
discard
of returnStmt:
discard
of importStmt:
discard
of fromImportStmt:
discard
of whileStmt:
discard
of forStmt:
discard
of forEachStmt:
discard
of NodeKind.blockStmt:
self.blockStmt(BlockStmt(node))
of yieldStmt:
discard
of awaitStmt:
discard
of deferStmt:
discard
of tryStmt:
discard
else:
self.error(&"invalid AST node of kind {node.kind} at statement(): {node} (This is an internal error and most likely a bug)") # TODO
proc declaration(self: Compiler, node: ASTNode) =
## Compiles all declarations
case node.kind:
of NodeKind.varDecl:
self.varDecl(VarDecl(node))
of funDecl, classDecl:
discard # TODO
else:
self.statement(node)
proc compile*(self: Compiler, ast: seq[ASTNode], file: string): Chunk =
## Compiles a sequence of AST nodes into a chunk
## object
self.chunk = newChunk()
self.ast = ast
self.file = file
self.names = @[]
self.staticNames = @[]
self.scopeDepth = 0
self.currentFunction = nil
self.current = 0
while not self.done():
self.declaration(self.step())
while self.staticNames.len() > 0:
# Gets rid of statically resolved locals
self.emitByte(Pop)
discard self.staticNames.pop()
if self.ast.len() > 0:
# *Technically* an empty program is a valid program
self.emitByte(OpCode.Return) # Exits the VM's main loop when used at the global scope
result = self.chunk
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