[Tolk] Pattern matching for expressions (switch-like behavior)

`match` can also be used for constant expressions, similar to `switch`:
> val nextValue = match (curValue) {
>     1 => 0,
>     0 => 1,
>     else => -1
> };

Only constant expressions are allowed on the left-hand side.
`else` is required for expression form but optional for statement form.

Author: tolk-vm

tolk-tester/tests/if-else-tests.tolk

@@ -72,6 +72,33 @@ fun test7() {
     // here we test that no "missing return" error
 }
 
+fun withNoElse(op: int): int {
+    if (op == 123) { return 100; }
+    if (op == 234) { return 200; }
+    if (op == 345) { return 300; }
+    throw 0xFF;
+}
+
+fun withElse(op: int): int {
+    if (op == 123) { return 100; }
+    else if (op == 234) { return 200; }
+    else if (op == 345) { return 300; }
+    return 0xFF;
+}
+
+fun withMatch(op: int): int {
+    match (op) {
+        123 => return 100,
+        234 => return 200,
+        345 => return 300,
+    }
+    throw 0xFF;
+}
+
+@method_id(108)
+fun test8(op: int) {
+    return (withNoElse(op), withElse(op), withMatch(op));
+}
 
 fun main() {
 
@@ -96,6 +123,8 @@ fun main() {
 @testcase | 105 | 3  | 7 222
 @testcase | 106 | -5 | -1
 @testcase | 106 | 5  | 5000
+@testcase | 108 | 123 | 100 100 100
+@testcase | 108 | 345 | 300 300 300
 
 @fif_codegen
 """
@@ -111,4 +140,82 @@ fun main() {
     50 EQINT	//  x '5
     IFNOTJMP:<{	//  x
 """
+
+@fif_codegen
+"""
+  withNoElse PROC:<{
+    //  op
+    DUP
+    123 EQINT
+    IFJMP:<{
+      DROP
+      100 PUSHINT
+    }>
+    DUP
+    234 PUSHINT
+    EQUAL
+    IFJMP:<{
+      DROP
+      200 PUSHINT
+    }>
+    345 PUSHINT
+    EQUAL
+    IFJMP:<{
+      300 PUSHINT
+    }>
+    255 THROW
+  }>
+"""
+
+@fif_codegen
+"""
+  withElse PROC:<{
+    //  op
+    DUP
+    123 EQINT
+    IFJMP:<{
+      DROP
+      100 PUSHINT
+    }>
+    DUP
+    234 PUSHINT
+    EQUAL
+    IFJMP:<{
+      DROP
+      200 PUSHINT
+    }>
+    345 PUSHINT
+    EQUAL
+    IFJMP:<{
+      300 PUSHINT
+    }>
+    8 PUSHPOW2DEC
+  }>
+"""
+
+@fif_codegen
+"""
+  withMatch PROC:<{
+    //  op
+    DUP
+    123 EQINT
+    IFJMP:<{
+      DROP
+      100 PUSHINT
+    }>
+    DUP
+    234 PUSHINT
+    EQUAL
+    IFJMP:<{
+      DROP
+      200 PUSHINT
+    }>
+    345 PUSHINT
+    EQUAL
+    IFJMP:<{
+      300 PUSHINT
+    }>
+    255 THROW
+  }>
+"""
 */

tolk-tester/tests/invalid-declaration/err-1808.tolk

@@ -0,0 +1,6 @@
+const C = match (10) { 10 => 0, else => -1 };
+
+/**
+@compilation_should_fail
+@stderr not a constant expression
+ */

tolk-tester/tests/invalid-semantics/err-4258.tolk

@@ -0,0 +1,13 @@
+fun f(x: int): int {
+    return match(x) {
+        -1 => -1,
+        f(0) => 0,
+        else => 1,
+    };
+}
+
+/**
+@compilation_should_fail
+@stderr not a constant expression
+@stderr f(0) => 0
+ */

tolk-tester/tests/invalid-semantics/err-4517.tolk

@@ -0,0 +1,14 @@
+global g: int;
+
+fun f(x: int): int {
+    match(x) {
+        -1 => -1,
+        g => 0,
+    };
+    return 10;
+}
+
+/**
+@compilation_should_fail
+@stderr symbol `g` is not a constant
+ */

tolk-tester/tests/invalid-syntax/err-3080.tolk

@@ -0,0 +1,11 @@
+fun f(x: int) {
+    return match(x) {
+        -1 => -1,
+        0 => 0
+    };
+}
+
+/**
+@compilation_should_fail
+@stderr `match` expression should have `else` branch
+ */

tolk-tester/tests/invalid-syntax/err-3419.tolk

@@ -0,0 +1,12 @@
+fun f(x: int) {
+    return match(x) {
+        -1 => -1,
+        else => 0,
+        0 => 0
+    };
+}
+
+/**
+@compilation_should_fail
+@stderr `else` branch should be the last
+ */

tolk-tester/tests/invalid-syntax/err-3457.tolk

@@ -13,6 +13,6 @@ fun main() {
 
 /**
 @compilation_should_fail
-@stderr `match` by expression is not supported yet
+@stderr symbol `asdf` is not a constant
 @stderr asdf => 2
  */

tolk-tester/tests/invalid-syntax/err-3837.tolk

@@ -0,0 +1,14 @@
+fun f(x: int) {
+    match(x) {
+        -1 => -1,
+        0 => 0,
+        else => 0,
+        else => -1
+    };
+}
+
+/**
+@compilation_should_fail
+@stderr duplicated `else` branch
+@stderr else => -1
+ */

tolk-tester/tests/invalid-syntax/err-3913.tolk

@@ -0,0 +1,8 @@
+fun f(x: bool) {
+    return match (x) { true => 0, true => -1 };
+}
+
+/**
+@compilation_should_fail
+@stderr `match` expression should have `else` branch
+ */