Initial work on inferring types

src/frontend/compiler.nim

@@ -522,11 +522,7 @@ proc declareName(self: Compiler, node: ASTNode) =
         else:
             discard  # TODO: Classes
 
-
-proc varDecl(self: Compiler, node: VarDecl) =
-    ## Compiles variable declarations
-    self.expression(node.value)
-    self.declareName(node)
+proc varDecl(self: Compiler, node: VarDecl)
 
 
 proc resolveStatic(self: Compiler, name: IdentExpr,
@@ -919,9 +915,54 @@ proc statement(self: Compiler, node: ASTNode) =
             self.expression(node)
 
 
+proc inferValueType(self: Compiler, node: ASTNode): ASTNode =
+    ## Infers the type of a given literal expression
+    case node.kind:
+        of listExpr:
+            return ListExpr(node).valueType
+        of dictExpr:
+            # It's not important that we don't use
+            # valueType here, we just need to return
+            # a non-nil value so we don't error out
+            return DictExpr(node).keyType
+        else:
+            discard  # TODO
+
+proc inferExprType(self: Compiler, node: Expression): ASTNode =
+    ## Infers the type of a given expression and
+    ## returns it
+    # TODO
+    
+
+
+proc inferDeclType(self: Compiler, node: Declaration): ASTNode =
+    ## Infers the type of a given declaration if it's
+    ## not already defined and returns it
+    case node.kind:
+        of funDecl:
+            var node = FunDecl(node)
+            if node.returnType != nil:
+                return node.returnType
+        of NodeKind.varDecl:
+            var node = VarDecl(node)
+            if node.valueType != nil:
+                return node.valueType
+        else:
+            return  # Unreachable
+
+
+proc varDecl(self: Compiler, node: VarDecl) =
+    ## Compiles variable declarations
+    if self.inferDeclType(node) == nil:
+        self.error(&"Cannot determine the type of '{node.name.token.lexeme}'")
+    self.expression(node.value)
+    self.declareName(node)
+
+
 proc funDecl(self: Compiler, node: FunDecl) =
     ## Compiles function declarations
-
+    if self.inferDeclType(node) == nil:
+        self.error(&"Cannot determine the return type of '{node.name.token.lexeme}'")
     # We store the current function
     var function = self.currentFunction
     self.currentFunction = node

src/frontend/meta/ast.nim

@@ -115,17 +115,13 @@ type
     FloatExpr* = ref object of LiteralExpr
     StrExpr* = ref object of LiteralExpr
 
-    # There are technically keywords, not literals!
-    TrueExpr* = ref object of ASTNode
-    FalseExpr* = ref object of ASTNode
-    NilExpr* = ref object of ASTNode
-    NanExpr* = ref object of ASTNode
-    InfExpr* = ref object of ASTNode
+    TrueExpr* = ref object of LiteralExpr
+    FalseExpr* = ref object of LiteralExpr
+    NilExpr* = ref object of LiteralExpr
+    NanExpr* = ref object of LiteralExpr
+    InfExpr* = ref object of LiteralExpr
 
-    # Although this is *technically* a literal, Nim doesn't
-    # allow us to redefine fields from supertypes so it's
-    # a tough luck for us
-    ListExpr* = ref object of ASTNode
+    ListExpr* = ref object of LiteralExpr
         members*: seq[ASTNode]
         valueType*: IdentExpr
 
@@ -310,8 +306,12 @@ proc isConst*(self: ASTNode): bool =
             return false
         
 
-# TODO: Fix (not all literals are constants)
-proc isLiteral*(self: ASTNode): bool {.inline.} = self.isConst()
+proc isLiteral*(self: ASTNode): bool {.inline.} = 
+    self.kind in {intExpr, hexExpr, binExpr, octExpr, 
+                  strExpr, falseExpr, trueExpr, infExpr, 
+                  nanExpr, floatExpr, nilExpr, listExpr,
+                  dictExpr, setExpr, tupleExpr
+                  }
 
 
 proc newIntExpr*(literal: Token): IntExpr =
@@ -344,11 +344,11 @@ proc newFloatExpr*(literal: Token): FloatExpr =
     result.token = literal
 
 
-proc newTrueExpr*(token: Token): LiteralExpr = LiteralExpr(kind: trueExpr, token: token)
-proc newFalseExpr*(token: Token): LiteralExpr = LiteralExpr(kind: falseExpr, token: token)
-proc newNaNExpr*(token: Token): LiteralExpr = LiteralExpr(kind: nanExpr, token: token)
-proc newNilExpr*(token: Token): LiteralExpr = LiteralExpr(kind: nilExpr, token: token)
-proc newInfExpr*(token: Token): LiteralExpr = LiteralExpr(kind: infExpr, token: token)
+proc newTrueExpr*(token: Token): LiteralExpr = LiteralExpr(kind: trueExpr, token: token, literal: token)
+proc newFalseExpr*(token: Token): LiteralExpr = LiteralExpr(kind: falseExpr, token: token, literal: token)
+proc newNaNExpr*(token: Token): LiteralExpr = LiteralExpr(kind: nanExpr, token: token, literal: token)
+proc newNilExpr*(token: Token): LiteralExpr = LiteralExpr(kind: nilExpr, token: token, literal: token)
+proc newInfExpr*(token: Token): LiteralExpr = LiteralExpr(kind: infExpr, token: token, literal: token)
 
 
 proc newStrExpr*(literal: Token): StrExpr =
@@ -391,18 +391,21 @@ proc newListExpr*(members: seq[ASTNode], token: Token): ListExpr =
     result = ListExpr(kind: listExpr)
     result.members = members
     result.token = token
+    result.literal = result.token
 
 
 proc newSetExpr*(members: seq[ASTNode], token: Token): SetExpr =
     result = SetExpr(kind: setExpr)
     result.members = members
     result.token = token
+    result.literal = result.token
 
 
 proc newTupleExpr*(members: seq[ASTNode], token: Token): TupleExpr =
     result = TupleExpr(kind: tupleExpr)
     result.members = members
     result.token = token
+    result.literal = result.token
 
 
 proc newDictExpr*(keys, values: seq[ASTNode], token: Token): DictExpr =

src/frontend/parser.nim

@@ -821,7 +821,7 @@ proc varDecl(self: Parser, isLet: bool = false, isConst: bool = false): ASTNode
         # the compiler may be able to infer
         # the type later!
         self.expect(Identifier, "expecting type name after ':'")
-    valueType = newIdentExpr(self.peek(-1))
+        valueType = newIdentExpr(self.peek(-1))
     if self.match(Equal):
         value = self.expression()
         if isConst and not value.isConst():

src/test.nim

@@ -143,6 +143,14 @@ when isMainModule:
             echo getCurrentExceptionMsg()
             echo &"Source line: {line}"
             echo " ".repeat(relPos.start + len("Source line: ")) & "^".repeat(relPos.stop - parser.getCurrentToken().lexeme.len())
+        except CompileError:
+            let lineNo = compiler.getCurrentNode().token.line
+            let relPos = tokenizer.getRelPos(lineNo)
+            let line = tokenizer.getSource().splitLines()[lineNo - 1].strip()
+            echo getCurrentExceptionMsg()
+            echo &"Source line: {line}"
+            echo " ".repeat(relPos.start + len("Source line: ")) & "^".repeat(relPos.stop - compiler.getCurrentNode().token.lexeme.len())
+
     quit(0)