fastc: fix production PGO self-build training (#31269)

doc/fastc.md

@@ -235,6 +235,11 @@ v -b fastc -nocache -o v_fastc1 cmd/v
 
 Each generation retains the full command-line entry and can compile programs with either
 the C or FastC backend. `-nocache` forces each generation to rebuild its generated C units.
+Clang production self-builds also exercise this full-compiler FastC path during PGO training
+when FastC is included. Compiler sources must stay within the FastC self-hosting subset for
+that training to complete.
+This path preserves enum shorthand types in parallel assignments and imported call arguments,
+and lowers flag enum `.has(flag)` calls on variables and imported function results.
 On macOS ARM64, standard full-compiler builds compile the owned native support files together
 so TinyCC processes shared SDK declarations once. Debug builds, custom preprocessing flags,
 and other native source sets retain separate compilation. FastC does not read their C headers.

vlib/v/compiler_tests/fastc_backend_test.v

@@ -50,6 +50,24 @@ fn run_with_v_environment(program string, args []string, flags string, vexe stri
 	return cmdexec.run(program, args)
 }
 
+fn test_full_compiler_fastc_pgo_training_generates_c() {
+	$if !macos && !linux {
+		return
+	}
+	root := os.join_path(os.vtmp_dir(), 'v_fastc_pgo_training_${os.getpid()}')
+	os.mkdir_all(root) or { panic(err) }
+	defer {
+		os.rmdir_all(root) or {}
+	}
+	output := os.join_path(root, 'cmd_v_fastc_training.c')
+	// Match the FastC profiling workload in vself without building an instrumented compiler.
+	training := run_with_v_environment(@VEXE, ['-nocache', '-gc', 'none', '-prealloc',
+		'-compile-backend', 'fastc', '-building-v', '-b', 'fastc', '-no-memory-limit', '-o', output,
+		os.join_path(fastc_backend_vroot, 'cmd', 'v')], '', @VEXE)
+	assert training.exit_code == 0, training.output
+	assert os.file_size(output) > 0
+}
+
 fn test_direct_fastc_compiler_entry_selects_selfhost_driver() {
 	$if !macos && !linux {
 		return

vlib/v/gen/fastc/expr.v

@@ -3668,7 +3668,9 @@ fn (g &Parser) streaming_call_argument_type(tokens []FastcExpressionToken) u32 {
 	}
 	arg_index := fastc_call_argument_index(tokens, open)
 	name := tokens[open - 1].lit
-	if open >= 2 && tokens[open - 2].tok == .dot {
+	if open >= 2 && tokens[open - 2].tok == .dot
+		&& !(open >= 3 && tokens[open - 3].tok == .name && tokens[open - 3].lit in g.imports
+			&& tokens[open - 3].lit !in g.locals && (open < 4 || tokens[open - 4].tok != .dot)) {
 		// `recv.method(…)`: resolve on the receiver's type; parameter_types[0] is the receiver.
 		receiver_start := fastc_method_receiver_start(tokens, open - 2)
 		receiver_tokens := tokens[receiver_start..open - 2]
@@ -3682,7 +3684,7 @@ fn (g &Parser) streaming_call_argument_type(tokens []FastcExpressionToken) u32 {
 			u32(0)
 		}
 	}
-	function_key := g.unqualified_function_key(name)
+	function_key := g.function_key_for_call(tokens, open - 1)
 	signature := g.functions[function_key] or { return u32(0) }
 	return if arg_index < signature.parameter_types.ids.len {
 		signature.parameter_types.ids[arg_index]

vlib/v/gen/fastc/flag_method_receiver_test.v

@@ -0,0 +1,89 @@
+module fastc
+
+import os
+import v.cmdexec
+
+fn test_fastc_selfhost_enum_context_and_imported_flag_receiver() {
+	$if !macos && !linux {
+		return
+	}
+	root := os.join_path(os.vtmp_dir(), 'fastc_flag_receiver_${os.getpid()}')
+	os.mkdir_all(os.join_path(root, 'features')) or { panic(err) }
+	defer { os.rmdir_all(root) or {} }
+	os.write_file(os.join_path(root, 'v.mod'), 'Module { name: "flag_receiver" }') or { panic(err) }
+	os.write_file(os.join_path(root, 'features', 'features.v'), r'module features
+
+@[flag]
+pub enum Flags {
+	read
+	write
+}
+
+pub struct Counter {
+pub mut:
+	value int
+}
+
+pub fn select(mut calls Counter) Flags {
+	calls.value++
+	return .read
+}
+
+pub fn accepts(flag Flags) bool {
+	return flag == .read
+}
+
+pub fn has_read(flag Flags) ?bool {
+	return flag.has(.read)
+}
+
+pub fn assign(mut flag Flags) {
+	mut count := 0
+	count, flag = 1, .read
+	assert count == 1
+}
+') or { panic(err) }
+	os.write_file(os.join_path(root, 'main.v'), r'module main
+
+import features
+
+fn main() {
+	mut calls := features.Counter{}
+	required := features.Flags.read
+	excluded := features.Flags.write
+	assert features.select(mut calls).has(required)
+	assert features.select(mut calls).has(.read)
+	assert !features.select(mut calls).has(excluded)
+	assert calls.value == 3
+	mut flag := features.Flags.write
+	assert flag.has(excluded)
+	mut count := 0
+	count, flag = 7, .read
+	assert count == 7
+	assert flag == .read
+	calls.value, flag = 8, .write
+	assert calls.value == 8
+	assert flag == .write
+	flag, calls.value = .read, 9
+	assert calls.value == 9
+	assert flag == .read
+	flag = .write
+	features.assign(mut flag)
+	assert flag == .read
+	assert features.accepts(if count == 7 { .read } else { .write })
+	assert !features.accepts(if count == 8 { .read } else { .write })
+	assert features.has_read(required) or { false }
+	assert !(features.has_read(excluded) or { true })
+	println("flag receivers work")
+}
+') or { panic(err) }
+	for backend in ['c', 'fastc'] {
+		executable := os.join_path(root, 'program_${backend}')
+		build := cmdexec.run(@VEXE, ['-b', backend, '-building-v', '-nocache', '-gc', 'none', '-o',
+			executable, root])
+		assert build.exit_code == 0, '${backend}: ${build.output}'
+		run := cmdexec.run(executable, [])
+		assert run.exit_code == 0, '${backend}: ${run.output}'
+		assert run.output.trim_space() == 'flag receivers work', '${backend}: ${run.output}'
+	}
+}

vlib/v/gen/fastc/render_calls.v

@@ -562,7 +562,7 @@ fn (g &Parser) render_c_struct_sizeof(tokens []FastcExpressionToken) ?FastcRende
 }
 
 fn (g &Parser) render_flag_method_expression(tokens []FastcExpressionToken, rendered_expression string) ?FastcRenderedExpression {
-	if tokens.len < 7 {
+	if tokens.len < 6 {
 		return none
 	}
 	mut rendered := rendered_expression
@@ -613,7 +613,10 @@ fn (g &Parser) render_flag_method_expression(tokens []FastcExpressionToken, rend
 		}
 		method := tokens[i].lit
 		raw_receiver_source := fastc_take_string(mut receiver)
-		receiver_source := g.render_member_receiver(receiver_tokens) or { raw_receiver_source }
+		receiver_source := g.render_member_receiver(receiver_tokens) or {
+			// Imported calls must resolve their C name and render their arguments too.
+			g.render_call_argument_expression(receiver_tokens, receiver_type) or { raw_receiver_source }
+		}
 		raw_argument_source := fastc_take_string(mut raw_argument)
 		c_argument_source := fastc_take_string(mut c_argument)
 		mut needle := '${raw_receiver_source}.${method}(${c_argument_source})'

vlib/v/gen/fastc/render_method_calls.v

@@ -266,6 +266,10 @@ fn (g &Parser) render_method_call_expression(tokens []FastcExpressionToken, rend
 		if !flags_processed && tokens[i].lit in ['has', 'set', 'clear'] {
 			flags_processed = true
 			if flags := g.render_flag_method_expression(tokens, rendered) {
+				call_end := fastc_matching_rpar(tokens, i + 1) or { -1 }
+				if receiver_start == 0 && call_end == tokens.len - 1 {
+					return flags
+				}
 				rendered = flags.source
 				changed = true
 			}

vlib/v/gen/fastc/stmt.v

@@ -964,11 +964,20 @@ fn (mut g Parser) parse_match_statement() !bool {
 		mut had_member_smartcast := false
 		mut member_smartcast_active := false
 		common_numeric_type := fastc_match_common_numeric_variant(variant_types)
+		mut array_variant_count := 0
+		if variant_types.len > 1 {
+			// Keep this scan within the FastC self-hosting subset used by PGO training.
+			for variant_type in variant_types {
+				if flat.source_type_query(variant_type).has(.c_array_prefix) {
+					array_variant_count++
+				}
+			}
+		}
 		// Several struct variants in one arm (`FnTypeDecl, AliasTypeDecl { node.type_pos }`)
 		// may only read fields common to all of them, which V lays out compatibly, so a
 		// plain-local subject narrows through the first variant — mirroring the member-chain
 		// smart-cast below.
-		struct_multi_variant := variant_types.len > 1 && common_numeric_type == 0 && !variant_types.any(flat.source_type_query(it).has(.c_array_prefix))
+		struct_multi_variant := variant_types.len > 1 && common_numeric_type == 0 && array_variant_count == 0
 		smartcast_active := is_boxed && !is_else && (variant_types.len == 1 || common_numeric_type != 0) && subject_local != ''
 		if smartcast_active {
 			variant_cname := if common_numeric_type != 0 {
@@ -1027,7 +1036,7 @@ fn (mut g Parser) parse_match_statement() !bool {
 		// layout for array variants) is correct.
 		member_smartcast_type := flat.source_type_id(if variant_types.len == 1 {
 			flat.source_type_name(variant_types[0])
-		} else if variant_types.len > 1 && variant_types.all(flat.source_type_query(it).has(.c_array_prefix)) {
+		} else if variant_types.len > 1 && array_variant_count == variant_types.len {
 			'array'
 		} else if variant_types.len > 1 && common_numeric_type == 0 {
 			flat.source_type_name(variant_types[0])
@@ -2162,10 +2171,22 @@ fn (mut g Parser) parse_parallel_assignment(initial_names []string, initial_mut
 	if g.selfhost && names.len > 1 && g.parallel_rhs_is_option_tuple_or() {
 		return g.parse_parallel_option_tuple(names, mutability, is_declaration)
 	}
+	assignment_targets := if is_declaration {
+		[]FastcRenderedExpression{}
+	} else {
+		g.validate_parallel_assignment_targets(names)!
+	}
 	g.last_multi_return_types = flat.TypeTextList{ ids: ([]u32{}).clone() }
 	mut values := []string{}
 	mut value_types := []u32{}
+	previous_expected_type := g.expected_expression_type
 	for {
+		// Each assignment value takes its context from the corresponding target.
+		g.expected_expression_type = if values.len < assignment_targets.len {
+			assignment_targets[values.len].typ
+		} else {
+			u32(0)
+		}
 		item := g.read_expression([token.Token.comma, token.Token.semicolon, token.Token.rcbr])!
 		if item == '' {
 			return g.unsupported('empty parallel assignment')
@@ -2177,6 +2198,7 @@ fn (mut g Parser) parse_parallel_assignment(initial_names []string, initial_mut
 		}
 		g.next()
 	}
+	g.expected_expression_type = previous_expected_type
 	value := values[0]
 	if value == '' {
 		return g.unsupported('empty parallel assignment')
@@ -2186,11 +2208,6 @@ fn (mut g Parser) parse_parallel_assignment(initial_names []string, initial_mut
 		if values.len != names.len {
 			return g.unsupported('parallel assignment with ${names.len} targets and ${values.len} values')
 		}
-		assignment_targets := if is_declaration {
-			[]FastcRenderedExpression{}
-		} else {
-			g.validate_parallel_assignment_targets(names)!
-		}
 		mut temporaries := []string{cap: values.len}
 		for i, item in values {
 			temporary := g.temporary_name('parallel')
@@ -2228,11 +2245,6 @@ fn (mut g Parser) parse_parallel_assignment(initial_names []string, initial_mut
 	if component_types.len == 0 {
 		component_types = g.last_multi_return_types.ids.clone()
 	}
-	assignment_targets := if is_declaration {
-		[]FastcRenderedExpression{}
-	} else {
-		g.validate_parallel_assignment_targets(names)!
-	}
 	temporary := g.temporary_name('multi_return')
 	g.write_line('MultiReturn ${temporary} = (${value});')
 	for i, name in names {
@@ -2286,7 +2298,13 @@ fn (mut g Parser) finish_parallel_member_assignment(names []string, member_targe
 	g.last_multi_return_types = flat.TypeTextList{ ids: ([]u32{}).clone() }
 	mut values := []string{}
 	mut value_types := []u32{}
+	previous_expected_type := g.expected_expression_type
 	for {
+		g.expected_expression_type = if values.len < targets.len {
+			targets[values.len].typ
+		} else {
+			u32(0)
+		}
 		value := g.read_expression([token.Token.comma, token.Token.semicolon, token.Token.rcbr])!
 		if value == '' {
 			return g.unsupported('empty parallel assignment')
@@ -2298,6 +2316,7 @@ fn (mut g Parser) finish_parallel_member_assignment(names []string, member_targe
 		}
 		g.next()
 	}
+	g.expected_expression_type = previous_expected_type
 	g.consume_statement_end()
 	if values.len > 1 {
 		if values.len != targets.len {
@@ -2574,7 +2593,13 @@ fn (mut g Parser) parse_parallel_expression_assignment(first_source string, firs
 	g.last_multi_return_types = flat.TypeTextList{ ids: ([]u32{}).clone() }
 	mut values := []string{}
 	mut value_types := []u32{}
+	previous_expected_type := g.expected_expression_type
 	for {
+		g.expected_expression_type = if values.len < targets.len {
+			targets[values.len].typ
+		} else {
+			u32(0)
+		}
 		value := g.read_expression([token.Token.comma, token.Token.semicolon, token.Token.rcbr])!
 		if value == '' {
 			return g.unsupported('empty parallel assignment')
@@ -2586,6 +2611,7 @@ fn (mut g Parser) parse_parallel_expression_assignment(first_source string, firs
 		}
 		g.next()
 	}
+	g.expected_expression_type = previous_expected_type
 	g.consume_statement_end()
 	if values.len > 1 {
 		if values.len != targets.len {