diff --git a/ast/src/main/ast/pork.yml b/ast/src/main/ast/pork.yml
index 8ff561b..26c901b 100644
--- a/ast/src/main/ast/pork.yml
+++ b/ast/src/main/ast/pork.yml
@@ -18,6 +18,11 @@ types:
     - name: modifiers
       type: DefinitionModifiers
       required: true
+  TypeSpec:
+    parent: Node
+    values:
+    - name: symbol
+      type: Symbol
   DefinitionModifiers:
     values:
     - name: export
@@ -42,6 +47,8 @@ types:
       type: Symbol
     - name: value
       type: Expression
+    - name: typeSpec
+      type: TypeSpec?
   VarAssignment:
     parent: Expression
     namedElementValue: symbol
@@ -50,6 +57,8 @@ types:
       type: Symbol
     - name: value
       type: Expression
+    - name: typeSpec
+      type: TypeSpec?
   SetAssignment:
     parent: Expression
     values:
@@ -142,6 +151,8 @@ types:
     values:
     - name: symbol
       type: Symbol
+    - name: typeSpec
+      type: TypeSpec?
     - name: multiple
       type: Boolean
       defaultValue: "false"
@@ -155,6 +166,8 @@ types:
       type: Symbol
     - name: arguments
       type: List<ArgumentSpec>
+    - name: returnType
+      type: TypeSpec?
     - name: block
       type: Block?
     - name: nativeFunctionDescriptor
@@ -167,6 +180,8 @@ types:
       type: DefinitionModifiers
     - name: symbol
       type: Symbol
+    - name: typeSpec
+      type: TypeSpec?
     - name: value
       type: Expression
   If:
diff --git a/ast/src/main/graph/types.dot b/ast/src/main/graph/types.dot
index 03312f8..1b5c561 100644
--- a/ast/src/main/graph/types.dot
+++ b/ast/src/main/graph/types.dot
@@ -4,6 +4,7 @@ digraph A {
   type_Symbol [shape=box,label="Symbol"]
   type_Declaration [shape=box,label="Declaration"]
   type_Definition [shape=box,label="Definition"]
+  type_TypeSpec [shape=box,label="TypeSpec"]
   type_DefinitionModifiers [shape=box,label="DefinitionModifiers"]
   type_Block [shape=box,label="Block"]
   type_CompilationUnit [shape=box,label="CompilationUnit"]
@@ -44,6 +45,7 @@ digraph A {
   type_Node -> type_Symbol
   type_Node -> type_Declaration
   type_Node -> type_Definition
+  type_Node -> type_TypeSpec
   type_Node -> type_Block
   type_Node -> type_CompilationUnit
   type_Node -> type_ArgumentSpec
@@ -78,13 +80,16 @@ digraph A {
   type_Declaration -> type_ImportDeclaration
   type_Definition -> type_Symbol [style=dotted]
   type_Definition -> type_DefinitionModifiers [style=dotted]
+  type_TypeSpec -> type_Symbol [style=dotted]
   type_Block -> type_Expression [style=dotted]
   type_CompilationUnit -> type_Declaration [style=dotted]
   type_CompilationUnit -> type_Definition [style=dotted]
   type_LetAssignment -> type_Symbol [style=dotted]
   type_LetAssignment -> type_Expression [style=dotted]
+  type_LetAssignment -> type_TypeSpec [style=dotted]
   type_VarAssignment -> type_Symbol [style=dotted]
   type_VarAssignment -> type_Expression [style=dotted]
+  type_VarAssignment -> type_TypeSpec [style=dotted]
   type_SetAssignment -> type_Symbol [style=dotted]
   type_SetAssignment -> type_Expression [style=dotted]
   type_InfixOperation -> type_Expression [style=dotted]
@@ -92,13 +97,16 @@ digraph A {
   type_FunctionCall -> type_Symbol [style=dotted]
   type_FunctionCall -> type_Expression [style=dotted]
   type_ArgumentSpec -> type_Symbol [style=dotted]
+  type_ArgumentSpec -> type_TypeSpec [style=dotted]
   type_FunctionDefinition -> type_DefinitionModifiers [style=dotted]
   type_FunctionDefinition -> type_Symbol [style=dotted]
   type_FunctionDefinition -> type_ArgumentSpec [style=dotted]
+  type_FunctionDefinition -> type_TypeSpec [style=dotted]
   type_FunctionDefinition -> type_Block [style=dotted]
   type_FunctionDefinition -> type_NativeFunctionDescriptor [style=dotted]
   type_LetDefinition -> type_DefinitionModifiers [style=dotted]
   type_LetDefinition -> type_Symbol [style=dotted]
+  type_LetDefinition -> type_TypeSpec [style=dotted]
   type_LetDefinition -> type_Expression [style=dotted]
   type_If -> type_Expression [style=dotted]
   type_If -> type_Block [style=dotted]
diff --git a/ast/src/main/kotlin/gay/pizza/pork/ast/FunctionLevelVisitor.kt b/ast/src/main/kotlin/gay/pizza/pork/ast/FunctionLevelVisitor.kt
index 9695277..d3aa92c 100644
--- a/ast/src/main/kotlin/gay/pizza/pork/ast/FunctionLevelVisitor.kt
+++ b/ast/src/main/kotlin/gay/pizza/pork/ast/FunctionLevelVisitor.kt
@@ -9,6 +9,9 @@ abstract class FunctionLevelVisitor<T> : NodeVisitor<T> {
   override fun visitSymbol(node: Symbol): T =
     throw RuntimeException("Visiting Symbol is not supported.")
 
+  override fun visitTypeSpec(node: TypeSpec): T =
+    throw RuntimeException("Visiting TypeSpec is not supported.")
+
   override fun visitLetDefinition(node: LetDefinition): T {
     topLevelUsedError("LetDefinition")
   }
diff --git a/ast/src/main/kotlin/gay/pizza/pork/ast/gen/ArgumentSpec.kt b/ast/src/main/kotlin/gay/pizza/pork/ast/gen/ArgumentSpec.kt
index f567510..d924db7 100644
--- a/ast/src/main/kotlin/gay/pizza/pork/ast/gen/ArgumentSpec.kt
+++ b/ast/src/main/kotlin/gay/pizza/pork/ast/gen/ArgumentSpec.kt
@@ -6,22 +6,23 @@ import kotlinx.serialization.Serializable
 
 @Serializable
 @SerialName("argumentSpec")
-class ArgumentSpec(val symbol: Symbol, val multiple: Boolean = false) : Node() {
+class ArgumentSpec(val symbol: Symbol, val typeSpec: TypeSpec?, val multiple: Boolean = false) : Node() {
   override val type: NodeType = NodeType.ArgumentSpec
 
   override fun <T> visitChildren(visitor: NodeVisitor<T>): List<T> =
-    visitor.visitNodes(symbol)
+    visitor.visitNodes(symbol, typeSpec)
 
   override fun <T> visit(visitor: NodeVisitor<T>): T =
     visitor.visitArgumentSpec(this)
 
   override fun equals(other: Any?): Boolean {
     if (other !is ArgumentSpec) return false
-    return other.symbol == symbol && other.multiple == multiple
+    return other.symbol == symbol && other.typeSpec == typeSpec && other.multiple == multiple
   }
 
   override fun hashCode(): Int {
     var result = symbol.hashCode()
+    result = 31 * result + typeSpec.hashCode()
     result = 31 * result + multiple.hashCode()
     result = 31 * result + type.hashCode()
     return result
diff --git a/ast/src/main/kotlin/gay/pizza/pork/ast/gen/FunctionDefinition.kt b/ast/src/main/kotlin/gay/pizza/pork/ast/gen/FunctionDefinition.kt
index 32c1a19..fc83075 100644
--- a/ast/src/main/kotlin/gay/pizza/pork/ast/gen/FunctionDefinition.kt
+++ b/ast/src/main/kotlin/gay/pizza/pork/ast/gen/FunctionDefinition.kt
@@ -6,24 +6,25 @@ import kotlinx.serialization.Serializable
 
 @Serializable
 @SerialName("functionDefinition")
-class FunctionDefinition(override val modifiers: DefinitionModifiers, override val symbol: Symbol, val arguments: List<ArgumentSpec>, val block: Block?, val nativeFunctionDescriptor: NativeFunctionDescriptor?) : Definition() {
+class FunctionDefinition(override val modifiers: DefinitionModifiers, override val symbol: Symbol, val arguments: List<ArgumentSpec>, val returnType: TypeSpec?, val block: Block?, val nativeFunctionDescriptor: NativeFunctionDescriptor?) : Definition() {
   override val type: NodeType = NodeType.FunctionDefinition
 
   override fun <T> visitChildren(visitor: NodeVisitor<T>): List<T> =
-    visitor.visitAll(listOf(symbol), arguments, listOf(block), listOf(nativeFunctionDescriptor))
+    visitor.visitAll(listOf(symbol), arguments, listOf(returnType), listOf(block), listOf(nativeFunctionDescriptor))
 
   override fun <T> visit(visitor: NodeVisitor<T>): T =
     visitor.visitFunctionDefinition(this)
 
   override fun equals(other: Any?): Boolean {
     if (other !is FunctionDefinition) return false
-    return other.modifiers == modifiers && other.symbol == symbol && other.arguments == arguments && other.block == block && other.nativeFunctionDescriptor == nativeFunctionDescriptor
+    return other.modifiers == modifiers && other.symbol == symbol && other.arguments == arguments && other.returnType == returnType && other.block == block && other.nativeFunctionDescriptor == nativeFunctionDescriptor
   }
 
   override fun hashCode(): Int {
     var result = modifiers.hashCode()
     result = 31 * result + symbol.hashCode()
     result = 31 * result + arguments.hashCode()
+    result = 31 * result + returnType.hashCode()
     result = 31 * result + block.hashCode()
     result = 31 * result + nativeFunctionDescriptor.hashCode()
     result = 31 * result + type.hashCode()
diff --git a/ast/src/main/kotlin/gay/pizza/pork/ast/gen/LetAssignment.kt b/ast/src/main/kotlin/gay/pizza/pork/ast/gen/LetAssignment.kt
index 46f5b90..635aaae 100644
--- a/ast/src/main/kotlin/gay/pizza/pork/ast/gen/LetAssignment.kt
+++ b/ast/src/main/kotlin/gay/pizza/pork/ast/gen/LetAssignment.kt
@@ -6,23 +6,24 @@ import kotlinx.serialization.Serializable
 
 @Serializable
 @SerialName("letAssignment")
-class LetAssignment(val symbol: Symbol, val value: Expression) : Expression() {
+class LetAssignment(val symbol: Symbol, val value: Expression, val typeSpec: TypeSpec?) : Expression() {
   override val type: NodeType = NodeType.LetAssignment
 
   override fun <T> visitChildren(visitor: NodeVisitor<T>): List<T> =
-    visitor.visitNodes(symbol, value)
+    visitor.visitNodes(symbol, value, typeSpec)
 
   override fun <T> visit(visitor: NodeVisitor<T>): T =
     visitor.visitLetAssignment(this)
 
   override fun equals(other: Any?): Boolean {
     if (other !is LetAssignment) return false
-    return other.symbol == symbol && other.value == value
+    return other.symbol == symbol && other.value == value && other.typeSpec == typeSpec
   }
 
   override fun hashCode(): Int {
     var result = symbol.hashCode()
     result = 31 * result + value.hashCode()
+    result = 31 * result + typeSpec.hashCode()
     result = 31 * result + type.hashCode()
     return result
   }
diff --git a/ast/src/main/kotlin/gay/pizza/pork/ast/gen/LetDefinition.kt b/ast/src/main/kotlin/gay/pizza/pork/ast/gen/LetDefinition.kt
index a09bb70..cdf7668 100644
--- a/ast/src/main/kotlin/gay/pizza/pork/ast/gen/LetDefinition.kt
+++ b/ast/src/main/kotlin/gay/pizza/pork/ast/gen/LetDefinition.kt
@@ -6,23 +6,24 @@ import kotlinx.serialization.Serializable
 
 @Serializable
 @SerialName("letDefinition")
-class LetDefinition(override val modifiers: DefinitionModifiers, override val symbol: Symbol, val value: Expression) : Definition() {
+class LetDefinition(override val modifiers: DefinitionModifiers, override val symbol: Symbol, val typeSpec: TypeSpec?, val value: Expression) : Definition() {
   override val type: NodeType = NodeType.LetDefinition
 
   override fun <T> visitChildren(visitor: NodeVisitor<T>): List<T> =
-    visitor.visitNodes(symbol, value)
+    visitor.visitNodes(symbol, typeSpec, value)
 
   override fun <T> visit(visitor: NodeVisitor<T>): T =
     visitor.visitLetDefinition(this)
 
   override fun equals(other: Any?): Boolean {
     if (other !is LetDefinition) return false
-    return other.modifiers == modifiers && other.symbol == symbol && other.value == value
+    return other.modifiers == modifiers && other.symbol == symbol && other.typeSpec == typeSpec && other.value == value
   }
 
   override fun hashCode(): Int {
     var result = modifiers.hashCode()
     result = 31 * result + symbol.hashCode()
+    result = 31 * result + typeSpec.hashCode()
     result = 31 * result + value.hashCode()
     result = 31 * result + type.hashCode()
     return result
diff --git a/ast/src/main/kotlin/gay/pizza/pork/ast/gen/NodeCoalescer.kt b/ast/src/main/kotlin/gay/pizza/pork/ast/gen/NodeCoalescer.kt
index f172721..12e3a87 100644
--- a/ast/src/main/kotlin/gay/pizza/pork/ast/gen/NodeCoalescer.kt
+++ b/ast/src/main/kotlin/gay/pizza/pork/ast/gen/NodeCoalescer.kt
@@ -95,6 +95,9 @@ class NodeCoalescer(val followChildren: Boolean = true, val handler: (Node) -> U
   override fun visitSymbolReference(node: SymbolReference): Unit =
     handle(node)
 
+  override fun visitTypeSpec(node: TypeSpec): Unit =
+    handle(node)
+
   override fun visitVarAssignment(node: VarAssignment): Unit =
     handle(node)
 
diff --git a/ast/src/main/kotlin/gay/pizza/pork/ast/gen/NodeParser.kt b/ast/src/main/kotlin/gay/pizza/pork/ast/gen/NodeParser.kt
index 88cc60d..353981a 100644
--- a/ast/src/main/kotlin/gay/pizza/pork/ast/gen/NodeParser.kt
+++ b/ast/src/main/kotlin/gay/pizza/pork/ast/gen/NodeParser.kt
@@ -70,6 +70,8 @@ interface NodeParser {
 
   fun parseSymbolReference(): SymbolReference
 
+  fun parseTypeSpec(): TypeSpec
+
   fun parseVarAssignment(): VarAssignment
 
   fun parseWhile(): While
diff --git a/ast/src/main/kotlin/gay/pizza/pork/ast/gen/NodeParserExtensions.kt b/ast/src/main/kotlin/gay/pizza/pork/ast/gen/NodeParserExtensions.kt
index 40bf2a1..9c8095a 100644
--- a/ast/src/main/kotlin/gay/pizza/pork/ast/gen/NodeParserExtensions.kt
+++ b/ast/src/main/kotlin/gay/pizza/pork/ast/gen/NodeParserExtensions.kt
@@ -7,6 +7,7 @@ fun NodeParser.parse(type: NodeType): Node =
     NodeType.Symbol -> parseSymbol()
     NodeType.Declaration -> parseDeclaration()
     NodeType.Definition -> parseDefinition()
+    NodeType.TypeSpec -> parseTypeSpec()
     NodeType.Block -> parseBlock()
     NodeType.CompilationUnit -> parseCompilationUnit()
     NodeType.LetAssignment -> parseLetAssignment()
diff --git a/ast/src/main/kotlin/gay/pizza/pork/ast/gen/NodeType.kt b/ast/src/main/kotlin/gay/pizza/pork/ast/gen/NodeType.kt
index 157c785..b09f5fe 100644
--- a/ast/src/main/kotlin/gay/pizza/pork/ast/gen/NodeType.kt
+++ b/ast/src/main/kotlin/gay/pizza/pork/ast/gen/NodeType.kt
@@ -37,6 +37,7 @@ enum class NodeType(val parent: NodeType? = null) {
   SuffixOperation(Expression),
   Symbol(Node),
   SymbolReference(Expression),
+  TypeSpec(Node),
   VarAssignment(Expression),
   While(Expression)
 }
diff --git a/ast/src/main/kotlin/gay/pizza/pork/ast/gen/NodeVisitor.kt b/ast/src/main/kotlin/gay/pizza/pork/ast/gen/NodeVisitor.kt
index caf5ef9..6c772bf 100644
--- a/ast/src/main/kotlin/gay/pizza/pork/ast/gen/NodeVisitor.kt
+++ b/ast/src/main/kotlin/gay/pizza/pork/ast/gen/NodeVisitor.kt
@@ -64,6 +64,8 @@ interface NodeVisitor<T> {
 
   fun visitSymbolReference(node: SymbolReference): T
 
+  fun visitTypeSpec(node: TypeSpec): T
+
   fun visitVarAssignment(node: VarAssignment): T
 
   fun visitWhile(node: While): T
diff --git a/ast/src/main/kotlin/gay/pizza/pork/ast/gen/NodeVisitorExtensions.kt b/ast/src/main/kotlin/gay/pizza/pork/ast/gen/NodeVisitorExtensions.kt
index 4e98113..466cc99 100644
--- a/ast/src/main/kotlin/gay/pizza/pork/ast/gen/NodeVisitorExtensions.kt
+++ b/ast/src/main/kotlin/gay/pizza/pork/ast/gen/NodeVisitorExtensions.kt
@@ -4,6 +4,7 @@ package gay.pizza.pork.ast.gen
 fun <T> NodeVisitor<T>.visit(node: Node): T =
   when (node) {
     is Symbol -> visitSymbol(node)
+    is TypeSpec -> visitTypeSpec(node)
     is Block -> visitBlock(node)
     is CompilationUnit -> visitCompilationUnit(node)
     is LetAssignment -> visitLetAssignment(node)
diff --git a/ast/src/main/kotlin/gay/pizza/pork/ast/gen/TypeSpec.kt b/ast/src/main/kotlin/gay/pizza/pork/ast/gen/TypeSpec.kt
new file mode 100644
index 0000000..2bfa7ed
--- /dev/null
+++ b/ast/src/main/kotlin/gay/pizza/pork/ast/gen/TypeSpec.kt
@@ -0,0 +1,28 @@
+// GENERATED CODE FROM PORK AST CODEGEN
+package gay.pizza.pork.ast.gen
+
+import kotlinx.serialization.SerialName
+import kotlinx.serialization.Serializable
+
+@Serializable
+@SerialName("typeSpec")
+class TypeSpec(val symbol: Symbol) : Node() {
+  override val type: NodeType = NodeType.TypeSpec
+
+  override fun <T> visitChildren(visitor: NodeVisitor<T>): List<T> =
+    visitor.visitNodes(symbol)
+
+  override fun <T> visit(visitor: NodeVisitor<T>): T =
+    visitor.visitTypeSpec(this)
+
+  override fun equals(other: Any?): Boolean {
+    if (other !is TypeSpec) return false
+    return other.symbol == symbol
+  }
+
+  override fun hashCode(): Int {
+    var result = symbol.hashCode()
+    result = 31 * result + type.hashCode()
+    return result
+  }
+}
diff --git a/ast/src/main/kotlin/gay/pizza/pork/ast/gen/VarAssignment.kt b/ast/src/main/kotlin/gay/pizza/pork/ast/gen/VarAssignment.kt
index 7b8e3ad..244cf31 100644
--- a/ast/src/main/kotlin/gay/pizza/pork/ast/gen/VarAssignment.kt
+++ b/ast/src/main/kotlin/gay/pizza/pork/ast/gen/VarAssignment.kt
@@ -6,23 +6,24 @@ import kotlinx.serialization.Serializable
 
 @Serializable
 @SerialName("varAssignment")
-class VarAssignment(val symbol: Symbol, val value: Expression) : Expression() {
+class VarAssignment(val symbol: Symbol, val value: Expression, val typeSpec: TypeSpec?) : Expression() {
   override val type: NodeType = NodeType.VarAssignment
 
   override fun <T> visitChildren(visitor: NodeVisitor<T>): List<T> =
-    visitor.visitNodes(symbol, value)
+    visitor.visitNodes(symbol, value, typeSpec)
 
   override fun <T> visit(visitor: NodeVisitor<T>): T =
     visitor.visitVarAssignment(this)
 
   override fun equals(other: Any?): Boolean {
     if (other !is VarAssignment) return false
-    return other.symbol == symbol && other.value == value
+    return other.symbol == symbol && other.value == value && other.typeSpec == typeSpec
   }
 
   override fun hashCode(): Int {
     var result = symbol.hashCode()
     result = 31 * result + value.hashCode()
+    result = 31 * result + typeSpec.hashCode()
     result = 31 * result + type.hashCode()
     return result
   }
diff --git a/evaluator/src/main/kotlin/gay/pizza/pork/evaluator/EvaluationVisitor.kt b/evaluator/src/main/kotlin/gay/pizza/pork/evaluator/EvaluationVisitor.kt
index 03869be..bd135d9 100644
--- a/evaluator/src/main/kotlin/gay/pizza/pork/evaluator/EvaluationVisitor.kt
+++ b/evaluator/src/main/kotlin/gay/pizza/pork/evaluator/EvaluationVisitor.kt
@@ -54,8 +54,6 @@ class EvaluationVisitor(root: Scope, val stack: CallStack) : FunctionLevelVisito
 
   override fun visitLongLiteral(node: LongLiteral): Any = node.value
 
-  override fun visitSymbol(node: Symbol): Any = None
-
   override fun visitFunctionCall(node: FunctionCall): Any {
     val arguments = node.arguments.map { it.visit(this) }
     val functionValue = currentScope.value(node.symbol.id) as CallableFunction
diff --git a/examples/fib.pork b/examples/fib.pork
index 609d729..af5a33d 100644
--- a/examples/fib.pork
+++ b/examples/fib.pork
@@ -1,5 +1,5 @@
 /* fibonacci sequence */
-func fib(n) {
+func fib(n: int32): int32 {
   if n < 2 {
     return n
   } else {
@@ -8,6 +8,6 @@ func fib(n) {
 }
 
 export func main() {
-  let result = fib(28)
+  let result: int32 = fib(28)
   println(result)
 }
diff --git a/ffi/src/main/kotlin/gay/pizza/pork/ffi/FfiNativeProvider.kt b/ffi/src/main/kotlin/gay/pizza/pork/ffi/FfiNativeProvider.kt
index 352b2df..7cae9e1 100644
--- a/ffi/src/main/kotlin/gay/pizza/pork/ffi/FfiNativeProvider.kt
+++ b/ffi/src/main/kotlin/gay/pizza/pork/ffi/FfiNativeProvider.kt
@@ -118,7 +118,7 @@ class FfiNativeProvider : ExpandedNativeProvider, NativeProvider {
     val buffer = HeapInvocationBuffer(context)
 
     val useFunctionArguments = functionArgumentSpecs ?: functionArguments.map {
-      ArgumentSpec(symbol = Symbol(""), multiple = false)
+      ArgumentSpec(symbol = Symbol(""), typeSpec = null, multiple = false)
     }
 
     for ((index, spec) in useFunctionArguments.withIndex()) {
diff --git a/ffi/src/main/kotlin/gay/pizza/pork/ffi/JavaAutogen.kt b/ffi/src/main/kotlin/gay/pizza/pork/ffi/JavaAutogen.kt
index 0bdb5bf..d56b4bc 100644
--- a/ffi/src/main/kotlin/gay/pizza/pork/ffi/JavaAutogen.kt
+++ b/ffi/src/main/kotlin/gay/pizza/pork/ffi/JavaAutogen.kt
@@ -147,11 +147,13 @@ class JavaAutogen(val javaClass: Class<*>) {
       arguments = parameterNames.map {
         ArgumentSpec(
           symbol = Symbol(it),
-          multiple = false
+          multiple = false,
+          typeSpec = null,
         )
       },
       nativeFunctionDescriptor = asNative(functionDefinition),
-      block = null
+      block = null,
+      returnType = null,
     )
 
   private fun asNative(functionDefinition: JavaFunctionDefinition): NativeFunctionDescriptor =
diff --git a/frontend/src/main/kotlin/gay/pizza/pork/frontend/scope/ExternalSymbolUsageAnalyzer.kt b/frontend/src/main/kotlin/gay/pizza/pork/frontend/scope/ExternalSymbolUsageAnalyzer.kt
index 0fb7b89..8fff0fd 100644
--- a/frontend/src/main/kotlin/gay/pizza/pork/frontend/scope/ExternalSymbolUsageAnalyzer.kt
+++ b/frontend/src/main/kotlin/gay/pizza/pork/frontend/scope/ExternalSymbolUsageAnalyzer.kt
@@ -119,6 +119,10 @@ class ExternalSymbolUsageAnalyzer : FunctionLevelVisitor<Unit>() {
     checkAndContribute(node.symbol)
   }
 
+  override fun visitTypeSpec(node: TypeSpec) {
+    checkAndContribute(node.symbol)
+  }
+
   override fun visitVarAssignment(node: VarAssignment) {
     internalSymbols.last().add(node.symbol)
     node.value.visit(this)
diff --git a/parser/src/main/kotlin/gay/pizza/pork/parser/Parser.kt b/parser/src/main/kotlin/gay/pizza/pork/parser/Parser.kt
index d7bb4b5..e30a953 100644
--- a/parser/src/main/kotlin/gay/pizza/pork/parser/Parser.kt
+++ b/parser/src/main/kotlin/gay/pizza/pork/parser/Parser.kt
@@ -8,7 +8,11 @@ class Parser(source: TokenSource, attribution: NodeAttribution) :
   ParserBase(source, attribution) {
   override fun parseArgumentSpec(): ArgumentSpec = produce(NodeType.ArgumentSpec) {
     val symbol = parseSymbol()
-    ArgumentSpec(symbol, next(TokenType.DotDotDot))
+    var typeSpec: TypeSpec? = null
+    if (next(TokenType.Colon)) {
+      typeSpec = parseTypeSpec()
+    }
+    ArgumentSpec(symbol, typeSpec = typeSpec, next(TokenType.DotDotDot))
   }
 
   override fun parseBlock(): Block = expect(NodeType.Block, TokenType.LeftCurly) {
@@ -213,7 +217,10 @@ class Parser(source: TokenSource, attribution: NodeAttribution) :
       parseArgumentSpec()
     }
     expect(TokenType.RightParentheses)
-
+    var returnType: TypeSpec? = null
+    if (next(TokenType.Colon)) {
+      returnType = parseTypeSpec()
+    }
     var native: NativeFunctionDescriptor? = null
     var block: Block? = null
     if (peek(TokenType.Native)) {
@@ -221,7 +228,7 @@ class Parser(source: TokenSource, attribution: NodeAttribution) :
     } else {
       block = parseBlock()
     }
-    FunctionDefinition(modifiers, name, arguments, block, native)
+    FunctionDefinition(modifiers = modifiers, symbol = name, arguments = arguments, returnType = returnType, block = block, nativeFunctionDescriptor = native)
   }
 
   override fun parseIf(): If = expect(NodeType.If, TokenType.If) {
@@ -280,18 +287,26 @@ class Parser(source: TokenSource, attribution: NodeAttribution) :
 
   override fun parseLetAssignment(): LetAssignment = expect(NodeType.LetAssignment, TokenType.Let) {
     val symbol = parseSymbol()
+    var typeSpec: TypeSpec? = null
+    if (next(TokenType.Colon)) {
+      typeSpec = parseTypeSpec()
+    }
     expect(TokenType.Equals)
     val value = parseExpression()
-    LetAssignment(symbol, value)
+    LetAssignment(symbol = symbol, typeSpec = typeSpec, value = value)
   }
 
   override fun parseLetDefinition(): LetDefinition = produce(NodeType.LetDefinition) {
     val definitionModifiers = parseDefinitionModifiers()
     expect(TokenType.Let)
     val name = parseSymbol()
+    var typeSpec: TypeSpec? = null
+    if (next(TokenType.Colon)) {
+      typeSpec = parseTypeSpec()
+    }
     expect(TokenType.Equals)
     val value = parseExpression()
-    LetDefinition(definitionModifiers, name, value)
+    LetDefinition(modifiers = definitionModifiers, symbol = name, typeSpec = typeSpec, value = value)
   }
 
   override fun parseListLiteral(): ListLiteral = expect(NodeType.ListLiteral, TokenType.LeftBracket) {
@@ -375,11 +390,19 @@ class Parser(source: TokenSource, attribution: NodeAttribution) :
     SymbolReference(parseSymbol())
   }
 
+  override fun parseTypeSpec(): TypeSpec = produce(NodeType.TypeSpec) {
+    TypeSpec(parseSymbol())
+  }
+
   override fun parseVarAssignment(): VarAssignment = expect(NodeType.VarAssignment, TokenType.Var) {
     val symbol = parseSymbol()
+    var typeSpec: TypeSpec? = null
+    if (next(TokenType.Colon)) {
+      typeSpec = parseTypeSpec()
+    }
     expect(TokenType.Equals)
     val value = parseExpression()
-    VarAssignment(symbol, value)
+    VarAssignment(symbol = symbol, typeSpec = typeSpec, value = value)
   }
 
   override fun parseWhile(): While = expect(NodeType.While, TokenType.While) {
diff --git a/parser/src/main/kotlin/gay/pizza/pork/parser/Printer.kt b/parser/src/main/kotlin/gay/pizza/pork/parser/Printer.kt
index a8b239c..c3abfaa 100644
--- a/parser/src/main/kotlin/gay/pizza/pork/parser/Printer.kt
+++ b/parser/src/main/kotlin/gay/pizza/pork/parser/Printer.kt
@@ -113,6 +113,10 @@ class Printer(buffer: StringBuilder) : NodeVisitor<Unit> {
   override fun visitLetAssignment(node: LetAssignment) {
     append("let ")
     visit(node.symbol)
+    if (node.typeSpec != null) {
+      append(": ")
+      visit(node.typeSpec!!)
+    }
     append(" = ")
     visit(node.value)
   }
@@ -121,6 +125,10 @@ class Printer(buffer: StringBuilder) : NodeVisitor<Unit> {
     visitDefinitionModifiers(node.modifiers)
     append("let ")
     visit(node.symbol)
+    if (node.typeSpec != null) {
+      append(": ")
+      visit(node.typeSpec!!)
+    }
     append(" = ")
     visit(node.value)
   }
@@ -129,9 +137,17 @@ class Printer(buffer: StringBuilder) : NodeVisitor<Unit> {
     visit(node.symbol)
   }
 
+  override fun visitTypeSpec(node: TypeSpec) {
+    visit(node.symbol)
+  }
+
   override fun visitVarAssignment(node: VarAssignment) {
     append("var ")
     visit(node.symbol)
+    if (node.typeSpec != null) {
+      append(": ")
+      visit(node.typeSpec!!)
+    }
     append(" = ")
     visit(node.value)
   }
@@ -209,6 +225,10 @@ class Printer(buffer: StringBuilder) : NodeVisitor<Unit> {
       }
     }
     append(") ")
+    if (node.returnType != null) {
+      append(": ")
+      visit(node.returnType!!)
+    }
     if (node.block != null) {
       visit(node.block!!)
     }
diff --git a/support/pork-idea/src/main/kotlin/gay/pizza/pork/idea/psi/gen/PorkElementFactory.kt b/support/pork-idea/src/main/kotlin/gay/pizza/pork/idea/psi/gen/PorkElementFactory.kt
index 93cd476..46b86d0 100644
--- a/support/pork-idea/src/main/kotlin/gay/pizza/pork/idea/psi/gen/PorkElementFactory.kt
+++ b/support/pork-idea/src/main/kotlin/gay/pizza/pork/idea/psi/gen/PorkElementFactory.kt
@@ -11,6 +11,7 @@ object PorkElementFactory {
   fun create(node: ASTNode): PsiElement =
     when (PorkElementTypes.nodeTypeFor(node.elementType)) {
       NodeType.Symbol -> SymbolElement(node)
+      NodeType.TypeSpec -> TypeSpecElement(node)
       NodeType.Block -> BlockElement(node)
       NodeType.CompilationUnit -> CompilationUnitElement(node)
       NodeType.LetAssignment -> LetAssignmentElement(node)
diff --git a/support/pork-idea/src/main/kotlin/gay/pizza/pork/idea/psi/gen/TypeSpecElement.kt b/support/pork-idea/src/main/kotlin/gay/pizza/pork/idea/psi/gen/TypeSpecElement.kt
new file mode 100644
index 0000000..a22173d
--- /dev/null
+++ b/support/pork-idea/src/main/kotlin/gay/pizza/pork/idea/psi/gen/TypeSpecElement.kt
@@ -0,0 +1,15 @@
+// GENERATED CODE FROM PORK AST CODEGEN
+package gay.pizza.pork.idea.psi.gen
+
+import com.intellij.lang.ASTNode
+import com.intellij.navigation.ItemPresentation
+import gay.pizza.pork.idea.psi.PorkElementHelpers
+import javax.swing.Icon
+
+class TypeSpecElement(node: ASTNode) : PorkElement(node) {
+  override fun getIcon(flags: Int): Icon? =
+    PorkElementHelpers.iconOf(this)
+
+  override fun getPresentation(): ItemPresentation? =
+    PorkElementHelpers.presentationOf(this)
+}
diff --git a/tokenizer/src/main/kotlin/gay/pizza/pork/tokenizer/TokenType.kt b/tokenizer/src/main/kotlin/gay/pizza/pork/tokenizer/TokenType.kt
index db70ebb..57db02b 100644
--- a/tokenizer/src/main/kotlin/gay/pizza/pork/tokenizer/TokenType.kt
+++ b/tokenizer/src/main/kotlin/gay/pizza/pork/tokenizer/TokenType.kt
@@ -50,6 +50,7 @@ enum class TokenType(vararg val properties: TokenTypeProperty) {
   Mod(ManyChars("mod"), KeywordFamily),
   Rem(ManyChars("rem"), KeywordFamily),
   Comma(SingleChar(',')),
+  Colon(SingleChar(':')),
   DotDotDot(ManyChars("...")),
   DotDot(ManyChars(".."), Promotion('.', DotDotDot)),
   Dot(SingleChar('.'), Promotion('.', DotDot)),