Add constant variables to E2 (#2769)

data/expression2/tests/compiler/compiler/restrictions/const_assign.txt

@@ -0,0 +1,5 @@
+## SHOULD_FAIL:COMPILE
+
+const X = 5
+
+X = 2

data/expression2/tests/compiler/compiler/restrictions/const_redeclare.txt

@@ -0,0 +1,4 @@
+## SHOULD_FAIL:COMPILE
+
+const Y = 2
+const Y = 1

data/expression2/tests/compiler/compiler/restrictions/const_redeclare_local.txt

@@ -0,0 +1,4 @@
+## SHOULD_FAIL:COMPILE
+
+const X = 5
+local X = 2

data/expression2/tests/compiler/compiler/restrictions/const_redeclare_multi.txt

@@ -0,0 +1,4 @@
+## SHOULD_FAIL:COMPILE
+
+const Z = "Foo"
+A=Z="Y"

data/expression2/tests/compiler/parser/const.txt

@@ -0,0 +1,4 @@
+## SHOULD_PASS:COMPILE
+
+const Var = 5
+const Xyz = "test"

lua/entities/gmod_wire_expression2/base/compiler.lua

@@ -23,7 +23,7 @@ end, "compiler_quota_check")
 ---@field function { [1]: string, [2]: EnvFunction}?
 ---@field ops integer
 
----@alias VarData { type: string, trace_if_unused: Trace?, initialized: boolean, depth: integer }
+---@alias VarData { type: string, trace_if_unused: Trace?, const: boolean, initialized: boolean, depth: integer }
 
 ---@class Scope
 ---@field parent Scope?
@@ -917,6 +917,8 @@ local CompileVisitors = {
 			-- Local declaration. Fastest case.
 			local var_name = data[2][1][1].value
 			self:AssertW(not self.scope.vars[var_name], "Do not redeclare existing variable " .. var_name, trace)
+			self:Assert(not self.scope.vars[var_name] or not self.scope.vars[var_name].const, "Cannot redeclare constant variable", trace)
+
 			self.scope:DeclVar(var_name, { initialized = true, trace_if_unused = data[2][1][1].trace, type = value_ty })
 			return function(state) ---@param state RuntimeContext
 				state.Scope[var_name] = value(state)
@@ -973,6 +975,7 @@ local CompileVisitors = {
 					end
 				else
 					self:Assert(existing.type == value_ty, "Cannot assign type (" .. value_ty .. ") to variable of type (" .. existing.type .. ")", trace)
+					self:Assert(not existing.const, "Cannot assign to constant variable " .. var, trace)
 					existing.initialized = true
 
 					local id = existing.depth
@@ -1029,6 +1032,17 @@ local CompileVisitors = {
 		end
 	end,
 
+	---@param data { [1]: Token<string>, [2]: Node }
+	[NodeVariant.Const] = function (self, trace, data)
+		local name, expr, expr_ty = data[1].value, self:CompileExpr(data[2])
+		self:Assert(not self.scope.vars[name], "Cannot redeclare existing variable " .. name, trace)
+		self.scope:DeclVar(name, { type = expr_ty, initialized = true, const = true, trace_if_unused = data[1].trace })
+
+		return function(state)
+			state.Scope[name] = expr(state)
+		end
+	end,
+
 	---@param data Token<string>
 	[NodeVariant.Increment] = function (self, trace, data)
 		-- Transform V-- to V = V + 1

lua/entities/gmod_wire_expression2/base/parser.lua

@@ -70,35 +70,36 @@ local NodeVariant = {
 	Decrement = 10, -- `--`
 	CompoundArithmetic = 11, -- `+=`, `-=`, `*=`, `/=`
 	Assignment = 12, -- `X = Y[2, number] = Z[2] = 5` or `local X = 5`
+	Const = 13, -- const X = 5
 
-	Switch = 13, -- `switch (<EXPR>) { case <EXPR>, <STMT>* default, <STMT*> }
-	Function = 14, -- `function test() {}`
-	Include = 15, -- #include "file"
-	Try = 16, -- try {} catch (Err) {}
+	Switch = 14, -- `switch (<EXPR>) { case <EXPR>, <STMT>* default, <STMT*> }
+	Function = 15, -- `function test() {}`
+	Include = 16, -- #include "file"
+	Try = 17, -- try {} catch (Err) {}
 
 	--- Compile time constructs
-	Event = 17, -- event tick() {}
+	Event = 18, -- event tick() {}
 
 	--- Expressions
-	ExprTernary = 18, -- `X ? Y : Z`
-	ExprDefault = 19, -- `X ?: Y`
-	ExprLogicalOp = 20, -- `|` `&` (Yes they are flipped.)
-	ExprBinaryOp = 21, -- `||` `&&` `^^`
-	ExprComparison = 22, -- `>` `<` `>=` `<=`
-	ExprEquals = 23, -- `==` `!=`
-	ExprBitShift = 24, -- `>>` `<<`
-	ExprArithmetic = 25, -- `+` `-` `*` `/` `^` `%`
-	ExprUnaryOp = 26, -- `-` `+` `!`
-	ExprMethodCall = 27, -- `<EXPR>:call()`
-	ExprIndex = 28,	-- `<EXPR>[<EXPR>, <type>?]`
-	ExprGrouped = 29, -- (<EXPR>)
-	ExprCall = 30, -- `call()`
-	ExprStringCall = 31, -- `""()` (Temporary until lambdas are made)
-	ExprUnaryWire = 32, -- `~Var` `$Var` `->Var`
-	ExprArray = 33, -- `array(1, 2, 3)` or `array(1 = 2, 2 = 3)`
-	ExprTable = 34, -- `table(1, 2, 3)` or `table(1 = 2, "test" = 3)`
-	ExprLiteral = 35, -- `"test"` `5e2` `4.023` `4j`
-	ExprIdent = 36 -- `Variable`
+	ExprTernary = 19, -- `X ? Y : Z`
+	ExprDefault = 20, -- `X ?: Y`
+	ExprLogicalOp = 21, -- `|` `&` (Yes they are flipped.)
+	ExprBinaryOp = 22, -- `||` `&&` `^^`
+	ExprComparison = 23, -- `>` `<` `>=` `<=`
+	ExprEquals = 24, -- `==` `!=`
+	ExprBitShift = 25, -- `>>` `<<`
+	ExprArithmetic = 26, -- `+` `-` `*` `/` `^` `%`
+	ExprUnaryOp = 27, -- `-` `+` `!`
+	ExprMethodCall = 28, -- `<EXPR>:call()`
+	ExprIndex = 29,	-- `<EXPR>[<EXPR>, <type>?]`
+	ExprGrouped = 30, -- (<EXPR>)
+	ExprCall = 31, -- `call()`
+	ExprStringCall = 32, -- `""()` (Temporary until lambdas are made)
+	ExprUnaryWire = 33, -- `~Var` `$Var` `->Var`
+	ExprArray = 34, -- `array(1, 2, 3)` or `array(1 = 2, 2 = 3)`
+	ExprTable = 35, -- `table(1, 2, 3)` or `table(1 = 2, "test" = 3)`
+	ExprLiteral = 36, -- `"test"` `5e2` `4.023` `4j`
+	ExprIdent = 37 -- `Variable`
 }
 
 Parser.Variant = NodeVariant
@@ -348,6 +349,16 @@ function Parser:Stmt()
 		self.index = self.index - 1
 	end
 
+	if self:Consume(TokenVariant.Keyword, Keyword.Const) then
+		local trace = self:Prev().trace
+
+		local name = self:Assert(self:Consume(TokenVariant.Ident), "Expected variable name after const")
+		self:Assert( self:Consume(TokenVariant.Operator, Operator.Ass), "Expected = for constant declaration" )
+		local value = self:Assert(self:Expr(), "Expected expression for constant declaration")
+
+		return Node.new(NodeVariant.Const, { name, value }, trace:stitch(self:Prev().trace))
+	end
+
 	local is_local, var = self:Consume(TokenVariant.Keyword, Keyword.Local), self:Consume(TokenVariant.Ident)
 	if not var then
 		self:Assert(not is_local, "Invalid operator (local) must be used for variable declaration.")

lua/entities/gmod_wire_expression2/core/e2lib.lua

@@ -420,36 +420,38 @@ local Keyword = {
 	Else = 3,
 	-- ``local``
 	Local = 4,
+	-- ``const``
+	Const = 5,
 	-- ``while``
-	While = 5,
+	While = 6,
 	-- ``for``
-	For = 6,
+	For = 7,
 	-- ``break``
-	Break = 7,
+	Break = 8,
 	-- ``continue``
-	Continue = 8,
+	Continue = 9,
 	-- ``switch``
-	Switch = 9,
+	Switch = 10,
 	-- ``case``
-	Case = 10,
+	Case = 11,
 	-- ``default``
-	Default = 11,
+	Default = 12,
 	-- ``foreach``
-	Foreach = 12,
+	Foreach = 13,
 	-- ``function``
-	Function = 13,
+	Function = 14,
 	-- ``return``
-	Return = 14,
+	Return = 15,
 	-- ``#include``
-	["#Include"] = 15,
+	["#Include"] = 16,
 	-- ``try``
-	Try = 16,
+	Try = 17,
 	-- ``catch``
-	Catch = 17,
+	Catch = 18,
 	-- ``do``
-	Do = 18,
+	Do = 19,
 	-- ``event``
-	Event = 19
+	Event = 20
 }
 
 E2Lib.Keyword = Keyword

lua/wire/client/text_editor/modes/e2.lua

@@ -29,6 +29,7 @@ local keywords = {
 	["function"] = { [true] = true },
 	["return"] = { [true] = true },
 	["local"]  = { [true] = true },
+	["const"] = { [true] = true },
 	["try"]    = { [true] = true },
 	["do"] = { [true] = true },
 	["event"] = { [true] = true },