From 5d3d14da538401aa669adc21985c484f3bdd4bba Mon Sep 17 00:00:00 2001
From: Nick Treleaven <n@trelsoft.com>
Date: Sun, 30 Aug 2020 07:56:18 +0100
Subject: [PATCH] cgen: support `typeof(expr).name` (#6253)

---
 vlib/v/checker/checker.v   |  8 ++++++++
 vlib/v/gen/cgen.v          | 21 +++++++++++++++++++++
 vlib/v/tests/typeof_test.v | 13 ++++++++++++-
 3 files changed, 41 insertions(+), 1 deletion(-)

diff --git a/vlib/v/checker/checker.v b/vlib/v/checker/checker.v
index 029ec9da22..53b9c96111 100644
--- a/vlib/v/checker/checker.v
+++ b/vlib/v/checker/checker.v
@@ -1474,6 +1474,14 @@ pub fn (mut c Checker) selector_expr(mut selector_expr ast.SelectorExpr) table.T
 		c.error('unknown selector expression', selector_expr.pos)
 		return table.void_type
 	}
+	if selector_expr.expr is ast.TypeOf as left {
+		if selector_expr.field_name == 'name' {
+			return table.string_type
+		} else {
+			c.error('expected `.name`, not `.$selector_expr.field_name` after `typeof` expression',
+				selector_expr.pos)
+		}
+	}
 	selector_expr.expr_type = typ
 	sym := c.table.get_type_symbol(c.unwrap_generic(typ))
 	field_name := selector_expr.field_name
diff --git a/vlib/v/gen/cgen.v b/vlib/v/gen/cgen.v
index db6e53c836..c743153178 100644
--- a/vlib/v/gen/cgen.v
+++ b/vlib/v/gen/cgen.v
@@ -2102,6 +2102,11 @@ fn (mut g Gen) expr(node ast.Expr) {
 			g.struct_init(node)
 		}
 		ast.SelectorExpr {
+			if node.expr is ast.TypeOf as left {
+				// typeof(expr).name
+				g.typeof_name(left)
+				return
+			}
 			sym := g.table.get_type_symbol(node.expr_type)
 			if sym.kind == .array_fixed {
 				assert node.field_name == 'len'
@@ -2157,6 +2162,22 @@ fn (mut g Gen) expr(node ast.Expr) {
 	}
 }
 
+// typeof(expr).name
+fn (mut g Gen) typeof_name(node ast.TypeOf) {
+	sym := g.table.get_type_symbol(node.expr_type)
+	if sym.kind == .array {
+		info := sym.info as table.Array
+		mut s := g.table.get_type_name(info.elem_type)
+		s = util.strip_main_name(s)
+		g.write('tos_lit("[]$s")')
+	} else if sym.kind == .sum_type {
+		// new typeof() must be known at compile-time
+		g.write('tos_lit("${util.strip_main_name(sym.name)}")')
+	} else {
+		g.typeof_expr(node)
+	}
+}
+
 fn (mut g Gen) typeof_expr(node ast.TypeOf) {
 	sym := g.table.get_type_symbol(node.expr_type)
 	if sym.kind == .sum_type {
diff --git a/vlib/v/tests/typeof_test.v b/vlib/v/tests/typeof_test.v
index 6a1b3a76c3..5870b426f7 100644
--- a/vlib/v/tests/typeof_test.v
+++ b/vlib/v/tests/typeof_test.v
@@ -6,6 +6,7 @@ fn test_typeof_on_simple_expressions() {
 	assert typeof(f64(1.0) * 12.2) == 'f64'
 	// assert typeof(1.0 * f32(12.2)) == 'f32'
 	assert typeof(a) == 'int'
+	assert typeof(a).name == 'int'
 	// a2 := 123
 	// assert typeof(a2) == 'any_int'
 	// assert typeof(42) == 'any_int'
@@ -19,6 +20,7 @@ fn test_typeof_on_atypes() {
 	astring := []string{}
 	assert typeof(aint) == 'array_int'
 	assert typeof(astring) == 'array_string'
+	assert typeof(astring).name == '[]string'
 }
 
 struct FooBar {
@@ -27,10 +29,12 @@ struct FooBar {
 
 fn test_typeof_on_structs() {
 	assert typeof(FooBar{}) == 'FooBar'
-	astruct_static := [2]FooBar
+	astruct_static := [2]FooBar{}
 	astruct_dynamic := [FooBar{}, FooBar{}]
 	assert typeof(astruct_static) == '[2]FooBar'
+	assert typeof(astruct_static).name == '[2]FooBar'
 	assert typeof(astruct_dynamic) == 'array_FooBar'
+	assert typeof(astruct_dynamic).name == '[]FooBar'
 }
 
 type MySumType = int | f32 | FooBar
@@ -51,6 +55,9 @@ fn test_typeof_on_sumtypes() {
 	assert typeof(a) == 'int'
 	assert typeof(b) == 'f32'
 	assert typeof(c) == 'FooBar'
+	assert typeof(a).name == 'MySumType'
+	assert typeof(b).name == 'MySumType'
+	assert typeof(c).name == 'MySumType'
 }
 
 //
@@ -96,4 +103,8 @@ fn test_typeof_on_fn() {
 	assert typeof(myfn2) == 'fn ()'
 	assert typeof(myfn3) == 'fn (int, string) byte'
 	assert typeof(myfn4) == 'fn () i8'
+	assert typeof(myfn).name == typeof(myfn)
+	assert typeof(myfn2).name == typeof(myfn2)
+	assert typeof(myfn3).name == typeof(myfn3)
+	assert typeof(myfn4).name == typeof(myfn4)
 }