From dbfb9c3a90a4c268d67c0de7aca09e5ddf3cf644 Mon Sep 17 00:00:00 2001
From: Felipe Pena <felipensp@gmail.com>
Date: Sat, 14 Jan 2023 11:20:12 -0300
Subject: [PATCH] cgen, checker: var type checking at compile-time (#16951)

---
 vlib/v/checker/comptime.v                     |   2 +-
 vlib/v/checker/if.v                           |  11 ++
 .../v/checker/tests/unknown_comptime_expr.out |  67 ++++-----
 vlib/v/checker/tests/unknown_comptime_expr.vv |  23 ++--
 vlib/v/gen/c/comptime.v                       | 130 +++++++++---------
 vlib/v/tests/var_type_is_checking2_test.v     |  60 ++++++++
 vlib/v/tests/var_type_is_checking_test.v      |  46 +++++++
 7 files changed, 226 insertions(+), 113 deletions(-)
 create mode 100644 vlib/v/tests/var_type_is_checking2_test.v
 create mode 100644 vlib/v/tests/var_type_is_checking_test.v

diff --git a/vlib/v/checker/comptime.v b/vlib/v/checker/comptime.v
index c43073a3c9..6f005153e5 100644
--- a/vlib/v/checker/comptime.v
+++ b/vlib/v/checker/comptime.v
@@ -551,7 +551,7 @@ fn (mut c Checker) comptime_if_branch(cond ast.Expr, pos token.Pos) ComptimeBran
 						} else {
 							.skip
 						}
-					} else if cond.left in [ast.SelectorExpr, ast.TypeNode] {
+					} else if cond.left in [ast.Ident, ast.SelectorExpr, ast.TypeNode] {
 						// `$if method.@type is string`
 						c.expr(cond.left)
 						return .unknown
diff --git a/vlib/v/checker/if.v b/vlib/v/checker/if.v
index bb76022b07..f196e92cba 100644
--- a/vlib/v/checker/if.v
+++ b/vlib/v/checker/if.v
@@ -94,6 +94,17 @@ fn (mut c Checker) if_expr(mut node ast.IfExpr) ast.Type {
 						} else {
 							.skip
 						}
+					} else if right is ast.ComptimeType && left is ast.Ident
+						&& (left as ast.Ident).info is ast.IdentVar {
+						is_comptime_type_is_expr = true
+						if var := left.scope.find_var(left.name) {
+							checked_type := c.unwrap_generic(var.typ)
+							skip_state = if c.table.is_comptime_type(checked_type, right as ast.ComptimeType) {
+								.eval
+							} else {
+								.skip
+							}
+						}
 					} else {
 						got_type := c.unwrap_generic((right as ast.TypeNode).typ)
 						sym := c.table.sym(got_type)
diff --git a/vlib/v/checker/tests/unknown_comptime_expr.out b/vlib/v/checker/tests/unknown_comptime_expr.out
index b97e13d8b1..f7eb905b4f 100644
--- a/vlib/v/checker/tests/unknown_comptime_expr.out
+++ b/vlib/v/checker/tests/unknown_comptime_expr.out
@@ -1,42 +1,35 @@
-vlib/v/checker/tests/unknown_comptime_expr.vv:5:6: error: `foo` is mut and may have changed since its definition
-    3 | fn main() {
-    4 |     mut foo := 0
-    5 |     $if foo == 0 {}
+vlib/v/checker/tests/unknown_comptime_expr.vv:7:6: error: `foo` is mut and may have changed since its definition
+    5 | fn main() {
+    6 |     mut foo := 0
+    7 |     $if foo == 0 {
       |         ~~~
-    6 | 
-    7 |     bar := unknown_at_ct()
-vlib/v/checker/tests/unknown_comptime_expr.vv:8:6: error: definition of `bar` is unknown at compile time
-    6 | 
-    7 |     bar := unknown_at_ct()
-    8 |     $if bar == 0 {}
+    8 |     }
+    9 |
+vlib/v/checker/tests/unknown_comptime_expr.vv:11:6: error: definition of `bar` is unknown at compile time
+    9 | 
+   10 |     bar := unknown_at_ct()
+   11 |     $if bar == 0 {
       |         ~~~
-    9 | }
-   10 |
-vlib/v/checker/tests/unknown_comptime_expr.vv:13:6: error: undefined ident: `huh`
-   11 | fn if_is() {
-   12 |     s := S1{}
-   13 |     $if huh.typ is T {}
+   12 |     }
+   13 | }
+vlib/v/checker/tests/unknown_comptime_expr.vv:17:6: error: undefined ident: `huh`
+   15 | fn if_is() {
+   16 |     s := S1{}
+   17 |     $if huh.typ is T {
       |         ~~~
-   14 |     $if s is int {}
-   15 |     $if s.i is 5 {}
-vlib/v/checker/tests/unknown_comptime_expr.vv:14:6: error: invalid `$if` condition: expected a type or a selector expression or an interface check
-   12 |     s := S1{}
-   13 |     $if huh.typ is T {}
-   14 |     $if s is int {}
-      |         ^
-   15 |     $if s.i is 5 {}
-   16 |     $if s.i is T {}
-vlib/v/checker/tests/unknown_comptime_expr.vv:15:13: error: invalid `$if` condition: expected a type
-   13 |     $if huh.typ is T {}
-   14 |     $if s is int {}
-   15 |     $if s.i is 5 {}
+   18 |     }
+   19 |     $if s is int {
+vlib/v/checker/tests/unknown_comptime_expr.vv:21:13: error: invalid `$if` condition: expected a type
+   19 |     $if s is int {
+   20 |     }
+   21 |     $if s.i is 5 {
       |                ^
-   16 |     $if s.i is T {}
-   17 | }
-vlib/v/checker/tests/unknown_comptime_expr.vv:16:13: error: unknown type `T`
-   14 |     $if s is int {}
-   15 |     $if s.i is 5 {}
-   16 |     $if s.i is T {}
+   22 |     }
+   23 |     $if s.i is T {
+vlib/v/checker/tests/unknown_comptime_expr.vv:23:13: error: unknown type `T`
+   21 |     $if s.i is 5 {
+   22 |     }
+   23 |     $if s.i is T {
       |                ^
-   17 | }
-   18 |
+   24 |     }
+   25 | }
diff --git a/vlib/v/checker/tests/unknown_comptime_expr.vv b/vlib/v/checker/tests/unknown_comptime_expr.vv
index c3734aeb8b..336adf4f97 100644
--- a/vlib/v/checker/tests/unknown_comptime_expr.vv
+++ b/vlib/v/checker/tests/unknown_comptime_expr.vv
@@ -1,22 +1,29 @@
-fn unknown_at_ct() int { return 0 }
+fn unknown_at_ct() int {
+	return 0
+}
 
 fn main() {
 	mut foo := 0
-	$if foo == 0 {}
+	$if foo == 0 {
+	}
 
 	bar := unknown_at_ct()
-	$if bar == 0 {}
+	$if bar == 0 {
+	}
 }
 
 fn if_is() {
 	s := S1{}
-	$if huh.typ is T {}
-	$if s is int {}
-	$if s.i is 5 {}
-	$if s.i is T {}
+	$if huh.typ is T {
+	}
+	$if s is int {
+	}
+	$if s.i is 5 {
+	}
+	$if s.i is T {
+	}
 }
 
 struct S1 {
 	i int
 }
-
diff --git a/vlib/v/gen/c/comptime.v b/vlib/v/gen/c/comptime.v
index 9a51190d05..89be81f220 100644
--- a/vlib/v/gen/c/comptime.v
+++ b/vlib/v/gen/c/comptime.v
@@ -378,6 +378,32 @@ fn (mut g Gen) comptime_if(node ast.IfExpr) {
 	}
 }
 
+fn (mut g Gen) get_expr_type(cond ast.Expr) ast.Type {
+	match cond {
+		ast.Ident {
+			return g.unwrap_generic(cond.obj.typ)
+		}
+		ast.TypeNode {
+			return g.unwrap_generic(cond.typ)
+		}
+		ast.SelectorExpr {
+			if cond.gkind_field == .typ {
+				return g.unwrap_generic(cond.name_type)
+			} else {
+				name := '${cond.expr}.${cond.field_name}'
+				if name in g.comptime_var_type_map {
+					return g.comptime_var_type_map[name]
+				} else {
+					return g.unwrap_generic(cond.typ)
+				}
+			}
+		}
+		else {
+			return ast.void_type
+		}
+	}
+}
+
 // returns the value of the bool comptime expression and if next branches may be discarded
 // returning `false` means the statements inside the $if can be skipped
 fn (mut g Gen) comptime_if_cond(cond ast.Expr, pkg_exist bool) (bool, bool) {
@@ -420,42 +446,11 @@ fn (mut g Gen) comptime_if_cond(cond ast.Expr, pkg_exist bool) (bool, bool) {
 				}
 				.key_is, .not_is {
 					left := cond.left
-					mut name := ''
-					if left is ast.TypeNode && cond.right is ast.ComptimeType {
-						checked_type := g.unwrap_generic(left.typ)
-						is_true := g.table.is_comptime_type(checked_type, cond.right)
-						if cond.op == .key_is {
-							if is_true {
-								g.write('1')
-							} else {
-								g.write('0')
-							}
-							return is_true, true
-						} else {
-							if is_true {
-								g.write('0')
-							} else {
-								g.write('1')
-							}
-							return !is_true, true
-						}
-					}
-					mut exp_type := ast.Type(0)
-					got_type := (cond.right as ast.TypeNode).typ
-					// Handle `$if x is Interface {`
-					// mut matches_interface := 'false'
-					if left is ast.TypeNode && cond.right is ast.TypeNode
-						&& g.table.sym(got_type).kind == .interface_ {
-						// `$if Foo is Interface {`
-						interface_sym := g.table.sym(got_type)
-						if interface_sym.info is ast.Interface {
-							// q := g.table.sym(interface_sym.info.types[0])
-							checked_type := g.unwrap_generic(left.typ)
-							// TODO PERF this check is run twice (also in the checker)
-							// store the result in a field
-							is_true := g.table.does_type_implement_interface(checked_type,
-								got_type)
-							// true // exp_type in interface_sym.info.types
+					if left in [ast.TypeNode, ast.Ident, ast.SelectorExpr]
+						&& cond.right in [ast.ComptimeType, ast.TypeNode] {
+						exp_type := g.get_expr_type(left)
+						if cond.right is ast.ComptimeType {
+							is_true := g.table.is_comptime_type(exp_type, cond.right)
 							if cond.op == .key_is {
 								if is_true {
 									g.write('1')
@@ -463,7 +458,7 @@ fn (mut g Gen) comptime_if_cond(cond ast.Expr, pkg_exist bool) (bool, bool) {
 									g.write('0')
 								}
 								return is_true, true
-							} else if cond.op == .not_is {
+							} else {
 								if is_true {
 									g.write('0')
 								} else {
@@ -471,27 +466,37 @@ fn (mut g Gen) comptime_if_cond(cond ast.Expr, pkg_exist bool) (bool, bool) {
 								}
 								return !is_true, true
 							}
-							// matches_interface = '/*iface:$got_type $exp_type*/ true'
-							//}
-						}
-					} else if left is ast.SelectorExpr {
-						if left.gkind_field == .typ {
-							exp_type = g.unwrap_generic(left.name_type)
 						} else {
-							name = '${left.expr}.${left.field_name}'
-							exp_type = g.comptime_var_type_map[name]
-						}
-					} else if left is ast.TypeNode {
-						// this is only allowed for generics currently, otherwise blocked by checker
-						exp_type = g.unwrap_generic(left.typ)
-					}
+							got_type := g.unwrap_generic((cond.right as ast.TypeNode).typ)
+							got_sym := g.table.sym(got_type)
 
-					if cond.op == .key_is {
-						g.write('${exp_type.idx()} == ${got_type.idx()} && ${exp_type.has_flag(.option)} == ${got_type.has_flag(.option)}')
-						return exp_type == got_type, true
-					} else {
-						g.write('${exp_type.idx()} != ${got_type.idx()}')
-						return exp_type != got_type, true
+							if got_sym.kind == .interface_ && got_sym.info is ast.Interface {
+								is_true := g.table.does_type_implement_interface(exp_type,
+									got_type)
+								if cond.op == .key_is {
+									if is_true {
+										g.write('1')
+									} else {
+										g.write('0')
+									}
+									return is_true, true
+								} else if cond.op == .not_is {
+									if is_true {
+										g.write('0')
+									} else {
+										g.write('1')
+									}
+									return !is_true, true
+								}
+							}
+							if cond.op == .key_is {
+								g.write('${exp_type.idx()} == ${got_type.idx()} && ${exp_type.has_flag(.option)} == ${got_type.has_flag(.option)}')
+								return exp_type == got_type, true
+							} else {
+								g.write('${exp_type.idx()} != ${got_type.idx()}')
+								return exp_type != got_type, true
+							}
+						}
 					}
 				}
 				.eq, .ne {
@@ -523,17 +528,7 @@ fn (mut g Gen) comptime_if_cond(cond ast.Expr, pkg_exist bool) (bool, bool) {
 				.key_in, .not_in {
 					if (cond.left is ast.TypeNode || cond.left is ast.SelectorExpr)
 						&& cond.right is ast.ArrayInit {
-						mut checked_type := ast.Type(0)
-						if cond.left is ast.SelectorExpr {
-							if cond.left.gkind_field == .typ {
-								checked_type = g.unwrap_generic(cond.left.name_type)
-							} else {
-								name := '${cond.left.expr}.${cond.left.field_name}'
-								checked_type = g.comptime_var_type_map[name]
-							}
-						} else {
-							checked_type = g.unwrap_generic((cond.left as ast.TypeNode).typ)
-						}
+						checked_type := g.get_expr_type(cond.left)
 
 						for expr in cond.right.exprs {
 							if expr is ast.ComptimeType {
@@ -767,6 +762,7 @@ fn (mut g Gen) comptime_for(node ast.ComptimeFor) {
 				g.writeln('\t${node.val_var}.indirections = ${field.typ.nr_muls()};')
 				//
 				g.comptime_var_type_map['${node.val_var}.typ'] = styp
+				g.comptime_var_type_map['${node.val_var}.unaliased_typ'] = unaliased_styp
 				g.stmts(node.stmts)
 				i++
 				g.writeln('}')
diff --git a/vlib/v/tests/var_type_is_checking2_test.v b/vlib/v/tests/var_type_is_checking2_test.v
new file mode 100644
index 0000000000..95b4546f45
--- /dev/null
+++ b/vlib/v/tests/var_type_is_checking2_test.v
@@ -0,0 +1,60 @@
+type MyAlias = string
+type MyAlias2 = rune
+
+struct Foo {
+	a string
+	b ?string
+	c MyAlias
+	d MyAlias2
+	e []int
+}
+
+fn is_t[T](val T) bool {
+	$if val is T {
+		return true
+	}
+	return false
+}
+
+fn test_main() {
+	a := Foo{}
+	$for field in Foo.fields {
+		$if field.unaliased_typ is ?string {
+			assert field.name == 'b'
+			println('is option string')
+		} $else $if field.unaliased_typ is string {
+			assert field.name in ['a', 'c']
+			println('is string')
+		} $else $if field.unaliased_typ is MyAlias {
+			assert false
+			println('is string')
+		} $else $if field.typ is MyAlias2 {
+			assert field.name == 'd'
+			println('is MyAlias')
+		} $else $if field.typ is []int {
+			assert field.name == 'e'
+			println('is int')
+		} $else {
+			assert false
+		}
+	}
+}
+
+fn test_generic() {
+	a := Foo{}
+	$for field in Foo.fields {
+		if is_t(field) {
+			println('T')
+			assert true
+		} else {
+			assert false
+		}
+		val := a.$(field.name)
+		if is_t(val) {
+			println('T')
+			assert true
+		} else {
+			assert false
+		}
+	}
+}
diff --git a/vlib/v/tests/var_type_is_checking_test.v b/vlib/v/tests/var_type_is_checking_test.v
new file mode 100644
index 0000000000..fdc10d15b7
--- /dev/null
+++ b/vlib/v/tests/var_type_is_checking_test.v
@@ -0,0 +1,46 @@
+struct Test {
+	a int
+	b ?int
+}
+
+fn test_main() {
+	hh := 1 // i64(4)
+	$if hh is $Int {
+		println('int')
+		assert true
+	} $else $if hh !is $Int {
+		println('string')
+		assert false
+	}
+
+	b := 1.2
+	$if b is $Int {
+		assert false
+	} $else $if b is $Float {
+		println('float')
+		assert true
+	}
+
+	c := true
+	$if c is bool {
+		println('bool')
+		assert true
+	}
+
+	d := Test{}
+	$if d.b is ?int {
+		println('?int')
+		assert true
+	}
+	$if d.a is ?int {
+		println('?int')
+		assert false
+	} $else $if d.a is int {
+		println('int')
+		assert true
+	}
+
+	$if d is Test {
+		println('Test')
+	}
+}