[Tolk] AST-based semantic analysis, get rid of Expr

This is a huge refactoring focusing on untangling compiler internals
(previously forked from FunC).
The goal is to convert AST directly to Op (a kind of IR representation),
doing all code analysis at AST level.

Noteable changes:
- AST-based semantic kernel includes: registering global symbols,
  scope handling and resolving local/global identifiers,
  lvalue/rvalue calc and check, implicit return detection,
  mutability analysis, pure/impure validity checks,
  simple constant folding
- values of `const` variables are calculated NOT based on CodeBlob,
  but via a newly-introduced AST-based constant evaluator
- AST vertices are now inherited from expression/statement/other;
  expression vertices have common properties (TypeExpr, lvalue/rvalue)
- symbol table is rewritten completely, SymDef/SymVal no longer exist,
  lexer now doesn't need to register identifiers
- AST vertices have references to symbols, filled at different
  stages of pipeline
- the remaining "FunC legacy part" is almost unchanged besides Expr
  which was fully dropped; AST is converted to Ops (IR) directly

Author: tolk-vm

tolk-tester/tests/allow_post_modification.tolk

@@ -2,85 +2,112 @@ fun unsafe_tuple<X>(x: X): tuple
     asm "NOP";
 
 fun inc(x: int, y: int): (int, int) {
-  return (x + y, y * 10);
+    return (x + y, y * 10);
 }
 fun `~inc`(mutate self: int, y: int): int {
-  val (newX, newY) = inc(self, y);
-  self = newX;
-  return newY;
+    val (newX, newY) = inc(self, y);
+    self = newX;
+    return newY;
 }
 
+fun eq<X>(v: X): X { return v; }
+fun eq2(v: (int, int)) { return v; }
+fun mul2(mutate dest: int, v: int): int { dest = v*2; return dest; }
+fun multens(mutate self: (int, int), v: (int, int)): (int, int) { var (f, s) = self; var (m1, m2) = v; self = (f*m1, s*m2); return self; }
+
 @method_id(11)
 fun test_return(x: int): (int, int, int, int, int, int, int) {
-  return (x, x.`~inc`(x / 20), x, x = x * 2, x, x += 1, x);
+    return (x, x.`~inc`(x / 20), x, x = x * 2, x, x += 1, x);
 }
 
 @method_id(12)
 fun test_assign(x: int): (int, int, int, int, int, int, int) {
-  var (x1: int, x2: int, x3: int, x4: int, x5: int, x6: int, x7: int) = (x, x.`~inc`(x / 20), x, x=x*2, x, x+=1, x);
-  return (x1, x2, x3, x4, x5, x6, x7);
+    var (x1: int, x2: int, x3: int, x4: int, x5: int, x6: int, x7: int) = (x, x.`~inc`(x / 20), x, x=x*2, x, x+=1, x);
+    return (x1, x2, x3, x4, x5, x6, x7);
 }
 
 @method_id(13)
 fun test_tuple(x: int): tuple {
-  var t: tuple = unsafe_tuple([x, x.`~inc`(x / 20), x, x = x * 2, x, x += 1, x]);
-  return t;
+    var t: tuple = unsafe_tuple([x, x.`~inc`(x / 20), x, x = x * 2, x, x += 1, x]);
+    return t;
 }
 
 @method_id(14)
 fun test_tuple_assign(x: int): (int, int, int, int, int, int, int) {
-  var [x1: int, x2: int, x3: int, x4: int, x5: int, x6: int, x7: int] = [x, x.`~inc`(x / 20), x, x = x * 2, x, x += 1, x];
-  return (x1, x2, x3, x4, x5, x6, x7);
+    var [x1: int, x2: int, x3: int, x4: int, x5: int, x6: int, x7: int] = [x, x.`~inc`(x / 20), x, x = x * 2, x, x += 1, x];
+    return (x1, x2, x3, x4, x5, x6, x7);
 }
 
 fun foo1(x1: int, x2: int, x3: int, x4: int, x5: int, x6: int, x7: int): (int, int, int, int, int, int, int) {
-  return (x1, x2, x3, x4, x5, x6, x7);
+    return (x1, x2, x3, x4, x5, x6, x7);
 }
 
 @method_id(15)
 fun test_call_1(x: int): (int, int, int, int, int, int, int) {
-  return foo1(x, x.`~inc`(x / 20), x, x = x * 2, x, x += 1, x);
+    return foo1(x, x.`~inc`(x / 20), x, x = x * 2, x, x += 1, x);
 }
 
 fun foo2(x1: int, x2: int, x3456: (int, int, int, int), x7: int): (int, int, int, int, int, int, int) {
-  var (x3: int, x4: int, x5: int, x6: int) = x3456;
-  return (x1, x2, x3, x4, x5, x6, x7);
+    var (x3: int, x4: int, x5: int, x6: int) = x3456;
+    return (x1, x2, x3, x4, x5, x6, x7);
 }
 
 @method_id(16)
 fun test_call_2(x: int): (int, int, int, int, int, int, int) {
-  return foo2(x, x.`~inc`(x / 20), (x, x = x * 2, x, x += 1), x);
+    return foo2(x, x.`~inc`(x / 20), (x, x = x * 2, x, x += 1), x);
 }
 
 fun asm_func(x1: int, x2: int, x3: int, x4: int, x5: int, x6: int, x7: int): (int, int, int, int, int, int, int)
-asm
-        (x4 x5 x6 x7 x1 x2 x3->0 1 2 3 4 5 6) "NOP";
+    asm (x4 x5 x6 x7 x1 x2 x3->0 1 2 3 4 5 6) "NOP";
 
 @method_id(17)
 fun test_call_asm_old(x: int): (int, int, int, int, int, int, int) {
-  return asm_func(x, x += 1, x, x, x.`~inc`(x / 20), x, x = x * 2);
+    return asm_func(x, x += 1, x, x, x.`~inc`(x / 20), x, x = x * 2);
 }
 
 @method_id(18)
 fun test_call_asm_new(x: int): (int, int, int, int, int, int, int) {
-  return asm_func(x, x.`~inc`(x / 20), x, x = x * 2, x, x += 1, x);
+    return asm_func(x, x.`~inc`(x / 20), x, x = x * 2, x, x += 1, x);
 }
 
 global xx: int;
 @method_id(19)
-fun test_global(x: int): (int, int, int, int, int, int, int) {
-  xx = x;
-  return (xx, xx.`~inc`(xx / 20), xx, xx = xx * 2, xx, xx += 1, xx);
+fun test_global(x: int) {
+    xx = x;
+    return (x, xx, xx.`~inc`(xx / 20), eq(xx += (x *= 0)), xx = xx * 2, xx, xx += 1, xx, x);
 }
 
 @method_id(20)
 fun test_if_else(x: int): (int, int, int, int, int) {
-  if (x > 10) {
-    return (x.`~inc`(8), x + 1, x = 1, x <<= 3, x);
-  } else {
-    xx = 9;
-    return (x, x.`~inc`(-4), x.`~inc`(-1), x >= 1, x = x + xx);
-  }
+    if (x > 10) {
+        return (x.`~inc`(8), x + 1, x = 1, x <<= 3, x);
+    } else {
+        xx = 9;
+        return (x, x.`~inc`(-4), x.`~inc`(-1), x >= 1, x = x + xx);
+    }
+}
+
+@method_id(21)
+fun test_assign_with_inner(x: int) {
+    return (x, x += 10, [(x, x += 20, eq(x -= 50), x)], eq2((x, x *= eq(x /= 2))));
+}
+
+@method_id(22)
+fun test_assign_with_mutate(x: int) {
+    return (x, mul2(mutate x, x += 5), x.`~inc`(mul2(mutate x, x)), x);
+}
+
+@method_id(23)
+fun test_assign_tensor(x: (int, int)) {
+    var fs = (0, 0);
+    return (x, x = (20, 30), fs = x.multens((1, 2)), fs.multens(multens(mutate x, (-1, -1))), x, fs);
+}
+
+global fs: (int, int);
+@method_id(24)
+fun test_assign_tensor_global(x: (int, int)) {
+    fs = (0, 0);
+    return (x, x = (20, 30), fs = x.multens((1, 2)), fs.multens(multens(mutate x, (-1, -1))), x, fs);
 }
 
 fun main() {
@@ -96,9 +123,13 @@ fun main() {
 @testcase | 16 | 100 | 100 50 105 210 210 211 211
 @testcase | 17 | 100 | 101 50 106 212 100 101 101
 @testcase | 18 | 100 | 210 210 211 211 100 50 105
-@testcase | 19 | 100 | 100 50 105 210 210 211 211
+@testcase | 19 | 100 | 100 100 50 105 210 210 211 211 0
 @testcase | 20 | 80  | 80 89 1 8 8
 @testcase | 20 | 9   | 9 -40 -10 -1 13
+@testcase | 21 | 100 | 100 110 [ 110 130 80 80 ] 80 3200
+@testcase | 22 | 100 | 100 210 4200 630
+@testcase | 23 | 1 1 | 1 1 20 30 20 60 -400 -3600 -20 -60 -400 -3600
+@testcase | 24 | 1 1 | 1 1 20 30 20 60 -400 -3600 -20 -60 -400 -3600
 
 @fif_codegen
 """
@@ -107,5 +138,5 @@ fun main() {
     inc CALLDICT // self newY
   }>
 """
-@code_hash 97139400653362069936987769894397430077752335662822462908581556703209313861576
+@code_hash 33262590582878205026101577472505372101182291690814957175155528952950621243206
 */

tolk-tester/tests/cells-slices.tolk

@@ -216,15 +216,15 @@ Note, that since 'compute-asm-ltr' became on be default, chaining methods codege
 """
   test6 PROC:<{
     //
-    NEWC	//  _1
-    1 PUSHINT	//  _1 _2=1
-    SWAP	//  _2=1 _1
+    NEWC	//  _0
+    1 PUSHINT	//  _0 _1=1
+    SWAP	//  _1=1 _0
     32 STU	//  _0
-    2 PUSHINT	//  _0 _6=2
-    SWAP	//  _6=2 _0
+    2 PUSHINT	//  _0 _5=2
+    SWAP	//  _5=2 _0
     32 STU	//  _0
-    3 PUSHINT	//  _0 _10=3
-    SWAP	//  _10=3 _0
+    3 PUSHINT	//  _0 _9=3
+    SWAP	//  _9=3 _0
     32 STU	//  _0
   }>
 """

tolk-tester/tests/codegen_check_demo.tolk

@@ -35,7 +35,7 @@ Below, I just give examples of @fif_codegen tag:
 """
 main PROC:<{
   // s
-  17 PUSHINT     //  s _3=17
+  17 PUSHINT     //  s _1=17
   OVER           //  s z=17 t
   WHILE:<{
     ...

tolk-tester/tests/invalid-call-1.tolk

@@ -5,5 +5,5 @@ fun main() {
 /**
 @compilation_should_fail
 The message is weird now, but later I'll rework error messages anyway.
-@stderr cannot apply expression of type int to an expression of type (): cannot unify type () -> ??3 with int
+@stderr cannot apply expression of type int to an expression of type (): cannot unify type () -> ??2 with int
  */

tolk-tester/tests/invalid-call-5.tolk

@@ -8,6 +8,6 @@ fun main() {
 
 /**
 @compilation_should_fail
-@stderr rvalue expected
+@stderr `_` can't be used as a value; it's a placeholder for a left side of assignment
 @stderr inc(_)
  */

tolk-tester/tests/invalid-const-1.tolk

@@ -0,0 +1,8 @@
+fun main() {
+    return 9999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999;
+}
+
+/**
+@compilation_should_fail
+@stderr invalid integer constant
+ */

tolk-tester/tests/invalid-mutate-1.tolk

@@ -7,5 +7,5 @@ fun cantAssignToVal() {
 
 /**
 @compilation_should_fail
-@stderr modifying an immutable variable `x`
+@stderr modifying immutable variable `x`
  */

tolk-tester/tests/invalid-mutate-11.tolk

@@ -4,5 +4,5 @@ fun load32(self: slice): int {
 
 /**
 @compilation_should_fail
-@stderr modifying `self` (call a mutating method), which is immutable by default
+@stderr modifying `self`, which is immutable by default
  */

tolk-tester/tests/invalid-mutate-2.tolk

@@ -6,5 +6,5 @@ fun cantAssignToVal() {
 
 /**
 @compilation_should_fail
-@stderr modifying an immutable variable `x`
+@stderr modifying immutable variable `x`
  */

tolk-tester/tests/invalid-mutate-3.tolk

@@ -7,5 +7,5 @@ fun cantAssignToConst() {
 
 /**
 @compilation_should_fail
-@stderr modifying an immutable variable `op_increase`
+@stderr modifying immutable constant
  */