diff --git a/.github/workflows/v_apps_and_modules_compile_ci.yml b/.github/workflows/v_apps_and_modules_compile_ci.yml
index ed84cab29e..b0fac889bd 100644
--- a/.github/workflows/v_apps_and_modules_compile_ci.yml
+++ b/.github/workflows/v_apps_and_modules_compile_ci.yml
@@ -47,17 +47,6 @@ jobs:
           ../v -prod .
           cd ..
 
-      - name: Build VEX
-        run: |
-          echo "Install Vex"
-          v install nedpals.vex
-          echo "Compile all of the Vex examples"
-          v should-compile-all ~/.vmodules/nedpals/vex/examples
-          echo "Compile the simple Vex example with -skip-unused"
-          v -skip-unused ~/.vmodules/nedpals/vex/examples/simple_example.v
-          echo "Run Vex Tests"
-          v test ~/.vmodules/nedpals/vex
-
       - name: Build vlang/pdf
         run: |
           v install pdf
@@ -172,3 +161,15 @@ jobs:
           v install pcre
           echo "Execute Tests"
           cd /tmp/adventofcode && v run verify.v
+
+
+#      - name: Build VEX
+#        run: |
+#          echo "Install Vex"
+#          v install nedpals.vex
+#          echo "Compile all of the Vex examples"
+#          v should-compile-all ~/.vmodules/nedpals/vex/examples
+#          echo "Compile the simple Vex example with -skip-unused"
+#          v -skip-unused ~/.vmodules/nedpals/vex/examples/simple_example.v
+#          echo "Run Vex Tests"
+#          v test ~/.vmodules/nedpals/vex
diff --git a/cmd/tools/measure/parser_speed.v b/cmd/tools/measure/parser_speed.v
index 93aa7436e9..831324d12d 100644
--- a/cmd/tools/measure/parser_speed.v
+++ b/cmd/tools/measure/parser_speed.v
@@ -19,10 +19,10 @@ fn main() {
 
 fn process_files(files []string) ! {
 	mut table := ast.new_table()
-	mut pref := pref.new_preferences()
-	pref.is_fmt = true
-	pref.skip_warnings = true
-	pref.output_mode = .silent
+	mut pref_ := pref.new_preferences()
+	pref_.is_fmt = true
+	pref_.skip_warnings = true
+	pref_.output_mode = .silent
 	mut sw := time.new_stopwatch()
 	mut total_us := i64(0)
 	mut total_bytes := i64(0)
@@ -35,7 +35,7 @@ fn process_files(files []string) ! {
 			continue
 		}
 		// do not measure the scanning, but only the parsing:
-		mut p := new_parser(f, .skip_comments, table, pref)
+		mut p := new_parser(f, .skip_comments, table, pref_)
 		///
 		sw.restart()
 		_ := p.parse()
@@ -49,12 +49,12 @@ fn process_files(files []string) ! {
 	println('${total_us:10}us ${total_tokens:10} ${total_bytes:10} ${(f64(total_tokens) / total_bytes):7.3} | speed: ${(f64(total_bytes) / total_us):2.5f} MB/s')
 }
 
-fn new_parser(path string, comments_mode scanner.CommentsMode, table &ast.Table, pref &pref.Preferences) &parser.Parser {
+fn new_parser(path string, comments_mode scanner.CommentsMode, table &ast.Table, pref_ &pref.Preferences) &parser.Parser {
 	mut p := &parser.Parser{
-		scanner: scanner.new_scanner_file(path, comments_mode, pref) or { panic(err) }
+		scanner: scanner.new_scanner_file(path, comments_mode, pref_) or { panic(err) }
 		comments_mode: comments_mode
 		table: table
-		pref: pref
+		pref: pref_
 		scope: &ast.Scope{
 			start_pos: 0
 			parent: table.global_scope
diff --git a/cmd/tools/measure/scanner_speed.v b/cmd/tools/measure/scanner_speed.v
index c690a3398f..d857b7f105 100644
--- a/cmd/tools/measure/scanner_speed.v
+++ b/cmd/tools/measure/scanner_speed.v
@@ -15,10 +15,10 @@ fn main() {
 }
 
 fn process_files(files []string) ! {
-	mut pref := pref.new_preferences()
-	pref.is_fmt = true
-	pref.skip_warnings = true
-	pref.output_mode = .silent
+	mut pref_ := pref.new_preferences()
+	pref_.is_fmt = true
+	pref_.skip_warnings = true
+	pref_.output_mode = .silent
 	mut sw := time.new_stopwatch()
 	mut total_us := i64(0)
 	mut total_bytes := i64(0)
@@ -31,7 +31,7 @@ fn process_files(files []string) ! {
 			continue
 		}
 		sw.restart()
-		s := scanner.new_scanner_file(f, .skip_comments, pref)!
+		s := scanner.new_scanner_file(f, .skip_comments, pref_)!
 		f_us := sw.elapsed().microseconds()
 		total_us += f_us
 		total_bytes += s.text.len
diff --git a/cmd/tools/vast/cjson.v b/cmd/tools/vast/cjson.v
index 976eaaaa2e..6d8c175c72 100644
--- a/cmd/tools/vast/cjson.v
+++ b/cmd/tools/vast/cjson.v
@@ -108,7 +108,7 @@ fn add_item_to_array(obj &C.cJSON, item &C.cJSON) {
 	C.cJSON_AddItemToArray(obj, item)
 }
 
-fn json_print(json &C.cJSON) string {
-	s := C.cJSON_Print(json)
+fn json_print(json_ &C.cJSON) string {
+	s := C.cJSON_Print(json_)
 	return unsafe { tos3(s) }
 }
diff --git a/cmd/tools/vast/vast.v b/cmd/tools/vast/vast.v
index 4e20a02b24..a7a26b1953 100644
--- a/cmd/tools/vast/vast.v
+++ b/cmd/tools/vast/vast.v
@@ -120,15 +120,15 @@ fn json(file string) string {
 	// use as permissive preferences as possible, so that `v ast`
 	// can print the AST of arbitrary V files, even .vsh or ones
 	// that require globals:
-	mut pref := &pref.Preferences{}
-	pref.fill_with_defaults()
-	pref.enable_globals = true
-	pref.is_fmt = true
+	mut pref_ := &pref.Preferences{}
+	pref_.fill_with_defaults()
+	pref_.enable_globals = true
+	pref_.is_fmt = true
 	//
 	mut t := Tree{
 		root: new_object()
 		table: ast.new_table()
-		pref: pref
+		pref: pref_
 	}
 	// parse file with comment
 	ast_file := parser.parse_file(file, t.table, .parse_comments, t.pref)
@@ -359,9 +359,9 @@ fn (t Tree) imports(nodes []ast.Import) &Node {
 	return import_array
 }
 
-fn (t Tree) errors(errors []errors.Error) &Node {
+fn (t Tree) errors(errors_ []errors.Error) &Node {
 	mut errs := new_array()
-	for e in errors {
+	for e in errors_ {
 		obj := new_object()
 		obj.add_terse('message', t.string_node(e.message))
 		obj.add_terse('file_path', t.string_node(e.file_path))
diff --git a/cmd/tools/vfmt.v b/cmd/tools/vfmt.v
index bd15da6407..f2564208e3 100644
--- a/cmd/tools/vfmt.v
+++ b/cmd/tools/vfmt.v
@@ -232,9 +232,9 @@ fn (mut foptions FormatOptions) post_process_file(file string, formatted_file_pa
 		}
 		diff_cmd := foptions.find_diff_cmd()
 		foptions.vlog('Using diff command: ${diff_cmd}')
-		diff := diff.color_compare_files(diff_cmd, file, formatted_file_path)
-		if diff.len > 0 {
-			println(diff)
+		diff_ := diff.color_compare_files(diff_cmd, file, formatted_file_path)
+		if diff_.len > 0 {
+			println(diff_)
 		}
 		return
 	}
diff --git a/cmd/tools/vpm.v b/cmd/tools/vpm.v
index dfa76c4f05..839e8b92cc 100644
--- a/cmd/tools/vpm.v
+++ b/cmd/tools/vpm.v
@@ -301,13 +301,13 @@ fn vpm_install_from_vcs(module_names []string, vcs_key string) {
 		vmod_path := os.join_path(final_module_path, 'v.mod')
 		if os.exists(vmod_path) {
 			data := os.read_file(vmod_path) or { return }
-			vmod := parse_vmod(data) or {
+			vmod_ := parse_vmod(data) or {
 				eprintln(err)
 				return
 			}
-			minfo := mod_name_info(vmod.name)
+			minfo := mod_name_info(vmod_.name)
 			if final_module_path != minfo.final_module_path {
-				println('Relocating module from "${name}" to "${vmod.name}" ( "${minfo.final_module_path}" ) ...')
+				println('Relocating module from "${name}" to "${vmod_.name}" ( "${minfo.final_module_path}" ) ...')
 				if os.exists(minfo.final_module_path) {
 					eprintln('Warning module "${minfo.final_module_path}" already exsits!')
 					eprintln('Removing module "${minfo.final_module_path}" ...')
@@ -330,10 +330,10 @@ fn vpm_install_from_vcs(module_names []string, vcs_key string) {
 					}
 					continue
 				}
-				println('Module "${name}" relocated to "${vmod.name}" successfully.')
+				println('Module "${name}" relocated to "${vmod_.name}" successfully.')
 				final_module_path = minfo.final_module_path
 			}
-			name = vmod.name
+			name = vmod_.name
 		}
 		resolve_dependencies(name, final_module_path, module_names)
 	}
@@ -646,13 +646,13 @@ fn resolve_dependencies(name string, module_path string, module_names []string)
 		return
 	}
 	data := os.read_file(vmod_path) or { return }
-	vmod := parse_vmod(data) or {
+	vmod_ := parse_vmod(data) or {
 		eprintln(err)
 		return
 	}
 	mut deps := []string{}
 	// filter out dependencies that were already specified by the user
-	for d in vmod.deps {
+	for d in vmod_.deps {
 		if d !in module_names {
 			deps << d
 		}
@@ -666,11 +666,11 @@ fn resolve_dependencies(name string, module_path string, module_names []string)
 
 fn parse_vmod(data string) !Vmod {
 	manifest := vmod.decode(data) or { return error('Parsing v.mod file failed, ${err}') }
-	mut vmod := Vmod{}
-	vmod.name = manifest.name
-	vmod.version = manifest.version
-	vmod.deps = manifest.dependencies
-	return vmod
+	mut vmod_ := Vmod{}
+	vmod_.name = manifest.name
+	vmod_.version = manifest.version
+	vmod_.deps = manifest.dependencies
+	return vmod_
 }
 
 fn get_working_server_url() string {
diff --git a/cmd/tools/vscan.v b/cmd/tools/vscan.v
index 052a6ccf10..7101e5714c 100644
--- a/cmd/tools/vscan.v
+++ b/cmd/tools/vscan.v
@@ -13,13 +13,13 @@ fn main() {
 	fp.description('\nScan .v source files, and print the V tokens contained in them.')
 	fp.arguments_description('PATH [PATH]...')
 	fp.limit_free_args_to_at_least(1)!
-	pref := pref.new_preferences()
+	pref_ := pref.new_preferences()
 	mut all_paths := fp.remaining_parameters()
 	for path in all_paths {
-		mut scanner := scanner.new_scanner_file(path, .parse_comments, pref)!
+		mut scanner_ := scanner.new_scanner_file(path, .parse_comments, pref_)!
 		mut tok := token.Token{}
 		for tok.kind != .eof {
-			tok = scanner.scan()
+			tok = scanner_.scan()
 			pos := tok.pos()
 			location := '${path}:${pos.line_nr + 1}:${pos.col + 1}:'
 			println('${location:-32} | pos: ${pos.pos:-5} | ${tok.debug()}')
diff --git a/examples/database/orm.v b/examples/database/orm.v
index affa5ab8b4..cadd66d2ba 100644
--- a/examples/database/orm.v
+++ b/examples/database/orm.v
@@ -1,5 +1,5 @@
 import db.sqlite
-import db.mysql
+import db.mysql as sql
 import db.pg
 
 [table: 'modules']
@@ -74,7 +74,7 @@ fn sqlite3_array() {
 }
 
 fn mysql_array() {
-	mut db := mysql.Connection{
+	mut db := sql.Connection{
 		host: 'localhost'
 		port: 3306
 		username: 'root'
@@ -186,7 +186,7 @@ fn sqlite3() {
 }
 
 fn mysql() {
-	mut conn := mysql.Connection{
+	mut conn := sql.Connection{
 		host: 'localhost'
 		port: 3306
 		username: 'root'
diff --git a/vlib/compress/deflate/deflate.v b/vlib/compress/deflate/deflate.v
index 406d52c6b9..87bd3f2e15 100644
--- a/vlib/compress/deflate/deflate.v
+++ b/vlib/compress/deflate/deflate.v
@@ -1,15 +1,15 @@
 module deflate
 
-import compress
+import compress as compr
 
 // compresses an array of bytes using deflate and returns the compressed bytes in a new array
 // Example: compressed := deflate.compress(b)?
 pub fn compress(data []u8) ![]u8 {
-	return compress.compress(data, 0)
+	return compr.compress(data, 0)
 }
 
 // decompresses an array of bytes using deflate and returns the decompressed bytes in a new array
 // Example: decompressed := deflate.decompress(b)?
 pub fn decompress(data []u8) ![]u8 {
-	return compress.decompress(data, 0)
+	return compr.decompress(data, 0)
 }
diff --git a/vlib/compress/gzip/gzip.v b/vlib/compress/gzip/gzip.v
index b99ab8cdad..fd5c682f25 100644
--- a/vlib/compress/gzip/gzip.v
+++ b/vlib/compress/gzip/gzip.v
@@ -3,13 +3,13 @@
 
 module gzip
 
-import compress
+import compress as compr
 import hash.crc32
 
 // compresses an array of bytes using gzip and returns the compressed bytes in a new array
 // Example: compressed := gzip.compress(b)?
 pub fn compress(data []u8) ![]u8 {
-	compressed := compress.compress(data, 0)!
+	compressed := compr.compress(data, 0)!
 	// header
 	mut result := [
 		u8(0x1f), // magic numbers (1F 8B)
@@ -139,7 +139,7 @@ pub fn decompress(data []u8, params DecompressParams) ![]u8 {
 	gzip_header := validate(data, params)!
 	header_length := gzip_header.length
 
-	decompressed := compress.decompress(data[header_length..data.len - 8], 0)!
+	decompressed := compr.decompress(data[header_length..data.len - 8], 0)!
 	length_expected := (u32(data[data.len - 4]) << 24) | (u32(data[data.len - 3]) << 16) | (u32(data[data.len - 2]) << 8) | data[data.len - 1]
 	if params.verify_length && decompressed.len != length_expected {
 		return error('length verification failed, got ${decompressed.len}, expected ${length_expected}')
diff --git a/vlib/compress/zlib/zlib.v b/vlib/compress/zlib/zlib.v
index 4816ef3d87..2967536ceb 100644
--- a/vlib/compress/zlib/zlib.v
+++ b/vlib/compress/zlib/zlib.v
@@ -1,17 +1,17 @@
 module zlib
 
-import compress
+import compress as compr
 
 // compresses an array of bytes using zlib and returns the compressed bytes in a new array
 // Example: compressed := zlib.compress(b)?
 pub fn compress(data []u8) ![]u8 {
 	// flags = TDEFL_WRITE_ZLIB_HEADER (0x01000)
-	return compress.compress(data, 0x01000)
+	return compr.compress(data, 0x01000)
 }
 
 // decompresses an array of bytes using zlib and returns the decompressed bytes in a new array
 // Example: decompressed := zlib.decompress(b)?
 pub fn decompress(data []u8) ![]u8 {
 	// flags = TINFL_FLAG_PARSE_ZLIB_HEADER (0x1)
-	return compress.decompress(data, 0x1)
+	return compr.decompress(data, 0x1)
 }
diff --git a/vlib/rand/rand.v b/vlib/rand/rand.v
index 4fdc03de50..2add309b48 100644
--- a/vlib/rand/rand.v
+++ b/vlib/rand/rand.v
@@ -411,14 +411,14 @@ pub fn (mut rng PRNG) exponential(lambda f64) f64 {
 // optional and the entire array is shuffled by default. Leave the end as 0 to
 // shuffle all elements until the end.
 [direct_array_access]
-pub fn (mut rng PRNG) shuffle[T](mut a []T, config config.ShuffleConfigStruct) ! {
-	config.validate_for(a)!
-	new_end := if config.end == 0 { a.len } else { config.end }
+pub fn (mut rng PRNG) shuffle[T](mut a []T, config_ config.ShuffleConfigStruct) ! {
+	config_.validate_for(a)!
+	new_end := if config_.end == 0 { a.len } else { config_.end }
 
 	// We implement the Fisher-Yates shuffle:
 	// https://en.wikipedia.org/wiki/Fisher%E2%80%93Yates_shuffle#The_modern_algorithm
 
-	for i in config.start .. new_end - 2 {
+	for i in config_.start .. new_end - 2 {
 		x := rng.int_in_range(i, new_end) or { i }
 		// swap
 		a_i := a[i]
@@ -429,9 +429,9 @@ pub fn (mut rng PRNG) shuffle[T](mut a []T, config config.ShuffleConfigStruct) !
 
 // shuffle_clone returns a random permutation of the elements in `a`.
 // The permutation is done on a fresh clone of `a`, so `a` remains unchanged.
-pub fn (mut rng PRNG) shuffle_clone[T](a []T, config config.ShuffleConfigStruct) ![]T {
+pub fn (mut rng PRNG) shuffle_clone[T](a []T, config_ config.ShuffleConfigStruct) ![]T {
 	mut res := a.clone()
-	rng.shuffle[T](mut res, config)!
+	rng.shuffle[T](mut res, config_)!
 	return res
 }
 
@@ -475,10 +475,10 @@ __global default_rng &PRNG
 
 // new_default returns a new instance of the default RNG. If the seed is not provided, the current time will be used to seed the instance.
 [manualfree]
-pub fn new_default(config config.PRNGConfigStruct) &PRNG {
+pub fn new_default(config_ config.PRNGConfigStruct) &PRNG {
 	mut rng := &wyrand.WyRandRNG{}
-	rng.seed(config.seed_)
-	unsafe { config.seed_.free() }
+	rng.seed(config_.seed_)
+	unsafe { config_.seed_.free() }
 	return &PRNG(rng)
 }
 
@@ -680,14 +680,14 @@ pub fn ascii(len int) string {
 // shuffle randomly permutates the elements in `a`. The range for shuffling is
 // optional and the entire array is shuffled by default. Leave the end as 0 to
 // shuffle all elements until the end.
-pub fn shuffle[T](mut a []T, config config.ShuffleConfigStruct) ! {
-	default_rng.shuffle[T](mut a, config)!
+pub fn shuffle[T](mut a []T, config_ config.ShuffleConfigStruct) ! {
+	default_rng.shuffle[T](mut a, config_)!
 }
 
 // shuffle_clone returns a random permutation of the elements in `a`.
 // The permutation is done on a fresh clone of `a`, so `a` remains unchanged.
-pub fn shuffle_clone[T](a []T, config config.ShuffleConfigStruct) ![]T {
-	return default_rng.shuffle_clone[T](a, config)
+pub fn shuffle_clone[T](a []T, config_ config.ShuffleConfigStruct) ![]T {
+	return default_rng.shuffle_clone[T](a, config_)
 }
 
 // choose samples k elements from the array without replacement.
@@ -716,13 +716,13 @@ pub fn bernoulli(p f64) !bool {
 
 // normal returns a normally distributed pseudorandom f64 in range `[0, 1)`.
 // NOTE: Use normal_pair() instead if you're generating a lot of normal variates.
-pub fn normal(conf config.NormalConfigStruct) !f64 {
-	return default_rng.normal(conf)
+pub fn normal(config_ config.NormalConfigStruct) !f64 {
+	return default_rng.normal(config_)
 }
 
 // normal_pair returns a pair of normally distributed pseudorandom f64 in range `[0, 1)`.
-pub fn normal_pair(conf config.NormalConfigStruct) !(f64, f64) {
-	return default_rng.normal_pair(conf)
+pub fn normal_pair(config_ config.NormalConfigStruct) !(f64, f64) {
+	return default_rng.normal_pair(config_)
 }
 
 // binomial returns the number of successful trials out of n when the
diff --git a/vlib/rand/sys/system_rng.c.v b/vlib/rand/sys/system_rng.c.v
index 4292811781..086dd8afc2 100644
--- a/vlib/rand/sys/system_rng.c.v
+++ b/vlib/rand/sys/system_rng.c.v
@@ -29,9 +29,9 @@ const (
 	u64_iter_count = calculate_iterations_for(64)
 )
 
-fn calculate_iterations_for(bits int) int {
-	base := bits / sys.rand_bitsize
-	extra := if bits % sys.rand_bitsize == 0 { 0 } else { 1 }
+fn calculate_iterations_for(bits_ int) int {
+	base := bits_ / sys.rand_bitsize
+	extra := if bits_ % sys.rand_bitsize == 0 { 0 } else { 1 }
 	return base + extra
 }
 
diff --git a/vlib/toml/parser/parser.v b/vlib/toml/parser/parser.v
index 72e7708991..f9efab38ef 100644
--- a/vlib/toml/parser/parser.v
+++ b/vlib/toml/parser/parser.v
@@ -160,15 +160,15 @@ fn (mut p Parser) peek(n int) !token.Token {
 		if n <= p.tokens.len {
 			return p.tokens[n - 1]
 		} else {
-			mut token := token.Token{}
+			mut token_ := token.Token{}
 			mut count := n - p.tokens.len
 			util.printdbg(@MOD + '.' + @STRUCT + '.' + @FN, 'buffering ${count} tokens...')
-			for token.kind != .eof && count != 0 {
-				token = p.scanner.scan()!
-				p.tokens << token
+			for token_.kind != .eof && count != 0 {
+				token_ = p.scanner.scan()!
+				p.tokens << token_
 				count--
 			}
-			return token
+			return token_
 		}
 	}
 }
diff --git a/vlib/toml/toml.v b/vlib/toml/toml.v
index c4631e763d..7005ee0608 100644
--- a/vlib/toml/toml.v
+++ b/vlib/toml/toml.v
@@ -84,9 +84,9 @@ pub fn parse_file(path string) !Doc {
 		scanner: scanner.new_scanner(scanner_config)!
 	}
 	mut p := parser.new_parser(parser_config)
-	ast := p.parse()!
+	ast_ := p.parse()!
 	return Doc{
-		ast: ast
+		ast: ast_
 	}
 }
 
@@ -102,9 +102,9 @@ pub fn parse_text(text string) !Doc {
 		scanner: scanner.new_scanner(scanner_config)!
 	}
 	mut p := parser.new_parser(parser_config)
-	ast := p.parse()!
+	ast_ := p.parse()!
 	return Doc{
-		ast: ast
+		ast: ast_
 	}
 }
 
@@ -122,9 +122,9 @@ pub fn parse(toml string) !Doc {
 		scanner: scanner.new_scanner(scanner_config)!
 	}
 	mut p := parser.new_parser(parser_config)
-	ast := p.parse()!
+	ast_ := p.parse()!
 	return Doc{
-		ast: ast
+		ast: ast_
 	}
 }
 
diff --git a/vlib/v/README.md b/vlib/v/README.md
index 151e3b1c8f..cb15bddea4 100644
--- a/vlib/v/README.md
+++ b/vlib/v/README.md
@@ -43,7 +43,7 @@ a new preference is created:
 ```v
 import v.pref
 
-pref := &pref.Preferences{}
+pref_ := &pref.Preferences{}
 ```
 
 and a new scope is created:
diff --git a/vlib/v/ast/type_size_test.v b/vlib/v/ast/type_size_test.v
index 1821627068..e9e7720e06 100644
--- a/vlib/v/ast/type_size_test.v
+++ b/vlib/v/ast/type_size_test.v
@@ -28,11 +28,11 @@ struct T08 {
 }
 
 fn test_type_size() {
-	mut pref := pref.new_preferences()
+	mut pref_ := pref.new_preferences()
 	$if x64 {
-		pref.m64 = true
+		pref_.m64 = true
 	}
-	mut b := builder.new_builder(pref)
+	mut b := builder.new_builder(pref_)
 	mut files := b.get_builtin_files()
 	b.set_module_lookup_paths()
 	parser.parse_files(files, b.table, b.pref)
diff --git a/vlib/v/builder/builder.v b/vlib/v/builder/builder.v
index fec6f7fdf7..d869f8fbe9 100644
--- a/vlib/v/builder/builder.v
+++ b/vlib/v/builder/builder.v
@@ -46,22 +46,22 @@ pub mut:
 	executable_exists     bool     // if the executable already exists, don't remove new executable after `v run`
 }
 
-pub fn new_builder(pref &pref.Preferences) Builder {
-	rdir := os.real_path(pref.path)
+pub fn new_builder(pref_ &pref.Preferences) Builder {
+	rdir := os.real_path(pref_.path)
 	compiled_dir := if os.is_dir(rdir) { rdir } else { os.dir(rdir) }
 	mut table := ast.new_table()
 	table.is_fmt = false
-	if pref.use_color == .always {
+	if pref_.use_color == .always {
 		util.emanager.set_support_color(true)
 	}
-	if pref.use_color == .never {
+	if pref_.use_color == .never {
 		util.emanager.set_support_color(false)
 	}
-	table.pointer_size = if pref.m64 { 8 } else { 4 }
+	table.pointer_size = if pref_.m64 { 8 } else { 4 }
 	mut msvc := MsvcResult{}
 	$if windows {
-		msvc = find_msvc(pref.m64) or {
-			if pref.ccompiler == 'msvc' {
+		msvc = find_msvc(pref_.m64) or {
+			if pref_.ccompiler == 'msvc' {
 				// verror('cannot find MSVC on this OS')
 			}
 			MsvcResult{
@@ -69,19 +69,19 @@ pub fn new_builder(pref &pref.Preferences) Builder {
 			}
 		}
 	}
-	util.timing_set_should_print(pref.show_timings || pref.is_verbose)
-	if pref.show_callgraph || pref.show_depgraph {
+	util.timing_set_should_print(pref_.show_timings || pref_.is_verbose)
+	if pref_.show_callgraph || pref_.show_depgraph {
 		dotgraph.start_digraph()
 	}
-	mut executable_name := pref.out_name
+	mut executable_name := pref_.out_name
 	$if windows {
 		executable_name += '.exe'
 	}
 	return Builder{
-		pref: pref
+		pref: pref_
 		table: table
-		checker: checker.new_checker(table, pref)
-		transformer: transformer.new_transformer_with_table(table, pref)
+		checker: checker.new_checker(table, pref_)
+		transformer: transformer.new_transformer_with_table(table, pref_)
 		compiled_dir: compiled_dir
 		cached_msvc: msvc
 		executable_exists: os.is_file(executable_name)
diff --git a/vlib/v/builder/compile.v b/vlib/v/builder/compile.v
index 6748d72abc..f8c800e2ef 100644
--- a/vlib/v/builder/compile.v
+++ b/vlib/v/builder/compile.v
@@ -10,10 +10,10 @@ import v.checker
 
 pub type FnBackend = fn (mut b Builder)
 
-pub fn compile(command string, pref &pref.Preferences, backend_cb FnBackend) {
-	check_if_output_folder_is_writable(pref)
+pub fn compile(command string, pref_ &pref.Preferences, backend_cb FnBackend) {
+	check_if_output_folder_is_writable(pref_)
 	// Construct the V object from command line arguments
-	mut b := new_builder(pref)
+	mut b := new_builder(pref_)
 	if b.should_rebuild() {
 		b.rebuild(backend_cb)
 	}
@@ -23,12 +23,12 @@ pub fn compile(command string, pref &pref.Preferences, backend_cb FnBackend) {
 	b.run_compiled_executable_and_exit()
 }
 
-fn check_if_output_folder_is_writable(pref &pref.Preferences) {
-	odir := os.dir(pref.out_name)
+fn check_if_output_folder_is_writable(pref_ &pref.Preferences) {
+	odir := os.dir(pref_.out_name)
 	// When pref.out_name is just the name of an executable, i.e. `./v -o executable main.v`
 	// without a folder component, just use the current folder instead:
 	mut output_folder := odir
-	if odir.len == pref.out_name.len {
+	if odir.len == pref_.out_name.len {
 		output_folder = os.getwd()
 	}
 	os.ensure_folder_is_writable(output_folder) or {
diff --git a/vlib/v/callgraph/callgraph.v b/vlib/v/callgraph/callgraph.v
index 45731324f5..2ca046707d 100644
--- a/vlib/v/callgraph/callgraph.v
+++ b/vlib/v/callgraph/callgraph.v
@@ -7,11 +7,11 @@ import v.dotgraph
 
 // callgraph.show walks the AST, starting at main() and prints a DOT output describing the calls
 // that function make transitively
-pub fn show(mut table ast.Table, pref &pref.Preferences, ast_files []&ast.File) {
+pub fn show(mut table ast.Table, pref_ &pref.Preferences, ast_files []&ast.File) {
 	mut mapper := &Mapper{
-		pref: pref
+		pref: pref_
 		table: table
-		dg: dotgraph.new('CallGraph', 'CallGraph for ${pref.path}', 'green')
+		dg: dotgraph.new('CallGraph', 'CallGraph for ${pref_.path}', 'green')
 	}
 	// Node14 [shape="box",label="PrivateBase",URL="$classPrivateBase.html"];
 	// Node15 -> Node9 [dir=back,color="midnightblue",fontsize=10,style="solid"];
diff --git a/vlib/v/checker/assign.v b/vlib/v/checker/assign.v
index a6ce0a321f..b76215efb0 100644
--- a/vlib/v/checker/assign.v
+++ b/vlib/v/checker/assign.v
@@ -312,7 +312,7 @@ fn (mut c Checker) assign_stmt(mut node ast.AssignStmt) {
 							}
 						}
 						// Check if variable name is already registered as imported module symbol
-						if c.file.imports.any(it.mod == left.name) {
+						if c.check_import_sym_conflict(left.name) {
 							c.error('duplicate of an import symbol `${left.name}`', left.pos)
 						}
 					}
diff --git a/vlib/v/checker/checker.v b/vlib/v/checker/checker.v
index 1b56b93922..93a9e1e99a 100644
--- a/vlib/v/checker/checker.v
+++ b/vlib/v/checker/checker.v
@@ -117,16 +117,16 @@ mut:
 	goto_labels                      map[string]ast.GotoLabel // to check for unused goto labels
 }
 
-pub fn new_checker(table &ast.Table, pref &pref.Preferences) &Checker {
+pub fn new_checker(table &ast.Table, pref_ &pref.Preferences) &Checker {
 	mut timers_should_print := false
 	$if time_checking ? {
 		timers_should_print = true
 	}
 	return &Checker{
 		table: table
-		pref: pref
+		pref: pref_
 		timers: util.new_timers(should_print: timers_should_print, label: 'checker')
-		match_exhaustive_cutoff_limit: pref.checker_match_exhaustive_cutoff_limit
+		match_exhaustive_cutoff_limit: pref_.checker_match_exhaustive_cutoff_limit
 	}
 }
 
@@ -4509,3 +4509,17 @@ fn (mut c Checker) deprecate_old_isreftype_and_sizeof_of_a_guessed_type(is_guess
 			pos)
 	}
 }
+
+fn (c &Checker) check_import_sym_conflict(ident string) bool {
+	for import_sym in c.file.imports {
+		// Check if alias exists or not
+		if !import_sym.alias.is_blank() {
+			if import_sym.alias == ident {
+				return true
+			}
+		} else if import_sym.mod == ident {
+			return true
+		}
+	}
+	return false
+}
diff --git a/vlib/v/checker/fn.v b/vlib/v/checker/fn.v
index 9ef4253166..6b074e0df6 100644
--- a/vlib/v/checker/fn.v
+++ b/vlib/v/checker/fn.v
@@ -249,6 +249,14 @@ fn (mut c Checker) fn_decl(mut node ast.FnDecl) {
 					}
 				}
 			}
+			// Check if parameter name is already registered as imported module symbol
+			if c.check_import_sym_conflict(param.name) {
+				c.error('duplicate of an import symbol `${param.name}`', param.pos)
+			}
+		}
+		// Check if function name is already registered as imported module symbol
+		if !node.is_method && c.check_import_sym_conflict(node.short_name) {
+			c.error('duplicate of an import symbol `${node.short_name}`', node.pos)
 		}
 	}
 	if node.language == .v && node.name.after_char(`.`) == 'init' && !node.is_method
diff --git a/vlib/v/checker/tests/fn_param_import_sym_conflict.out b/vlib/v/checker/tests/fn_param_import_sym_conflict.out
new file mode 100644
index 0000000000..548101e99f
--- /dev/null
+++ b/vlib/v/checker/tests/fn_param_import_sym_conflict.out
@@ -0,0 +1,80 @@
+vlib/v/checker/tests/fn_param_import_sym_conflict.vv:1:8: warning: module 'arrays' is imported but never used
+    1 | import arrays
+      |        ~~~~~~
+    2 | import maps
+    3 | import strings as strs
+vlib/v/checker/tests/fn_param_import_sym_conflict.vv:2:8: warning: module 'maps' is imported but never used
+    1 | import arrays
+    2 | import maps
+      |        ~~~~
+    3 | import strings as strs
+    4 |
+vlib/v/checker/tests/fn_param_import_sym_conflict.vv:3:8: warning: module 'strs (strings)' is imported but never used
+    1 | import arrays
+    2 | import maps
+    3 | import strings as strs
+      |        ~~~~~~~
+    4 |
+    5 | // FnDecl
+vlib/v/checker/tests/fn_param_import_sym_conflict.vv:6:6: error: duplicate of an import symbol `arrays`
+    4 |
+    5 | // FnDecl
+    6 | fn x(arrays []int) {
+      |      ~~~~~~
+    7 | }
+    8 |
+vlib/v/checker/tests/fn_param_import_sym_conflict.vv:9:1: error: duplicate of an import symbol `maps`
+    7 | }
+    8 |
+    9 | fn maps() {
+      | ~~~~~~~~~
+   10 | }
+   11 |
+vlib/v/checker/tests/fn_param_import_sym_conflict.vv:12:9: error: duplicate of an import symbol `arrays`
+   10 | }
+   11 |
+   12 | fn maps(arrays []int) {
+      |         ~~~~~~
+   13 | }
+   14 |
+vlib/v/checker/tests/fn_param_import_sym_conflict.vv:18:1: error: duplicate of an import symbol `strs`
+   16 | }
+   17 |
+   18 | fn strs() {
+      | ~~~~~~~~~
+   19 | }
+   20 |
+vlib/v/checker/tests/fn_param_import_sym_conflict.vv:24:5: error: duplicate of an import symbol `arrays`
+   22 | struct Foo {}
+   23 |
+   24 | fn (arrays Foo) x() {
+      |     ~~~~~~
+   25 | }
+   26 |
+vlib/v/checker/tests/fn_param_import_sym_conflict.vv:27:5: error: duplicate of an import symbol `arrays`
+   25 | }
+   26 |
+   27 | fn (arrays Foo) y(maps []int) {
+      |     ~~~~~~
+   28 | }
+   29 |
+vlib/v/checker/tests/fn_param_import_sym_conflict.vv:30:16: error: duplicate of an import symbol `arrays`
+   28 | }
+   29 |
+   30 | fn (foo Foo) z(arrays []int) {
+      |                ~~~~~~
+   31 | }
+   32 |
+vlib/v/checker/tests/fn_param_import_sym_conflict.vv:33:5: error: duplicate of an import symbol `arrays`
+   31 | }
+   32 |
+   33 | fn (arrays Foo) maps() {
+      |     ~~~~~~
+   34 | }
+   35 |
+vlib/v/checker/tests/fn_param_import_sym_conflict.vv:47:11: error: duplicate of an import symbol `arrays`
+   45 | // AnonFn
+   46 | fn y() {
+   47 |     _ := fn (arrays []int) {}
+      |              ~~~~~~
+   48 | }
\ No newline at end of file
diff --git a/vlib/v/checker/tests/fn_param_import_sym_conflict.vv b/vlib/v/checker/tests/fn_param_import_sym_conflict.vv
new file mode 100644
index 0000000000..4562fb225a
--- /dev/null
+++ b/vlib/v/checker/tests/fn_param_import_sym_conflict.vv
@@ -0,0 +1,48 @@
+import arrays
+import maps
+import strings as strs
+
+// FnDecl
+fn x(arrays []int) {
+}
+
+fn maps() {
+}
+
+fn maps(arrays []int) {
+}
+
+fn strings() {
+}
+
+fn strs() {
+}
+
+// FnDecl with receiver
+struct Foo {}
+
+fn (arrays Foo) x() {
+}
+
+fn (arrays Foo) y(maps []int) {
+}
+
+fn (foo Foo) z(arrays []int) {
+}
+
+fn (arrays Foo) maps() {
+}
+
+fn (foo Foo) arrays() {
+}
+
+fn (foo Foo) strings() {
+}
+
+fn (foo Foo) strs() {
+}
+
+// AnonFn
+fn y() {
+	_ := fn (arrays []int) {}
+}
diff --git a/vlib/v/doc/doc.v b/vlib/v/doc/doc.v
index 3dbb01c75c..a5bc7835b2 100644
--- a/vlib/v/doc/doc.v
+++ b/vlib/v/doc/doc.v
@@ -147,12 +147,12 @@ pub mut:
 pub fn new_vdoc_preferences() &pref.Preferences {
 	// vdoc should be able to parse as much user code as possible
 	// so its preferences should be permissive:
-	mut pref := &pref.Preferences{
+	mut pref_ := &pref.Preferences{
 		enable_globals: true
 		is_fmt: true
 	}
-	pref.fill_with_defaults()
-	return pref
+	pref_.fill_with_defaults()
+	return pref_
 }
 
 // new creates a new instance of a `Doc` struct.
diff --git a/vlib/v/eval/eval.v b/vlib/v/eval/eval.v
index 309bf9b2a2..46b68735f5 100644
--- a/vlib/v/eval/eval.v
+++ b/vlib/v/eval/eval.v
@@ -7,10 +7,10 @@ import v.ast
 import v.pref
 import v.util
 
-pub fn new_eval(table &ast.Table, pref &pref.Preferences) Eval {
+pub fn new_eval(table &ast.Table, pref_ &pref.Preferences) Eval {
 	return Eval{
 		table: table
-		pref: pref
+		pref: pref_
 	}
 }
 
diff --git a/vlib/v/fmt/fmt.v b/vlib/v/fmt/fmt.v
index e9e03a1b93..ee6ec22a28 100644
--- a/vlib/v/fmt/fmt.v
+++ b/vlib/v/fmt/fmt.v
@@ -61,11 +61,11 @@ pub struct FmtOptions {
 	source_text string
 }
 
-pub fn fmt(file ast.File, table &ast.Table, pref &pref.Preferences, is_debug bool, options FmtOptions) string {
+pub fn fmt(file ast.File, table &ast.Table, pref_ &pref.Preferences, is_debug bool, options FmtOptions) string {
 	mut f := Fmt{
 		file: file
 		table: table
-		pref: pref
+		pref: pref_
 		is_debug: is_debug
 		out: strings.new_builder(1000)
 		out_imports: strings.new_builder(200)
diff --git a/vlib/v/gen/c/cgen.v b/vlib/v/gen/c/cgen.v
index 33d20a81f4..534ec46dc6 100644
--- a/vlib/v/gen/c/cgen.v
+++ b/vlib/v/gen/c/cgen.v
@@ -254,13 +254,13 @@ struct GlobalConstDef {
 	is_precomputed bool     // can be declared as a const in C: primitive, and a simple definition
 }
 
-pub fn gen(files []&ast.File, table &ast.Table, pref &pref.Preferences) (string, string, string, []int) {
+pub fn gen(files []&ast.File, table &ast.Table, pref_ &pref.Preferences) (string, string, string, []int) {
 	// println('start cgen2')
 	mut module_built := ''
-	if pref.build_mode == .build_module {
+	if pref_.build_mode == .build_module {
 		for file in files {
-			if file.path.contains(pref.path)
-				&& file.mod.short_name == pref.path.all_after_last(os.path_separator).trim_right(os.path_separator) {
+			if file.path.contains(pref_.path)
+				&& file.mod.short_name == pref_.path.all_after_last(os.path_separator).trim_right(os.path_separator) {
 				module_built = file.mod.name
 				break
 			}
@@ -300,19 +300,19 @@ pub fn gen(files []&ast.File, table &ast.Table, pref &pref.Preferences) (string,
 		json_forward_decls: strings.new_builder(100)
 		sql_buf: strings.new_builder(100)
 		table: table
-		pref: pref
+		pref: pref_
 		fn_decl: 0
-		is_autofree: pref.autofree
+		is_autofree: pref_.autofree
 		indent: -1
 		module_built: module_built
 		timers_should_print: timers_should_print
 		timers: util.new_timers(should_print: timers_should_print, label: 'global_cgen')
 		inner_loop: &ast.empty_stmt
 		field_data_type: ast.Type(table.find_type_idx('FieldData'))
-		is_cc_msvc: pref.ccompiler == 'msvc'
-		use_segfault_handler: !('no_segfault_handler' in pref.compile_defines
-			|| pref.os in [.wasm32, .wasm32_emscripten])
-		static_modifier: if pref.parallel_cc { 'static' } else { '' }
+		is_cc_msvc: pref_.ccompiler == 'msvc'
+		use_segfault_handler: !('no_segfault_handler' in pref_.compile_defines
+			|| pref_.os in [.wasm32, .wasm32_emscripten])
+		static_modifier: if pref_.parallel_cc { 'static' } else { '' }
 		has_reflection: 'v.reflection' in table.modules
 		reflection_funcs: strings.new_builder(100)
 		reflection_others: strings.new_builder(100)
@@ -330,7 +330,7 @@ pub fn gen(files []&ast.File, table &ast.Table, pref &pref.Preferences) (string,
 	*/
 	// anon fn may include assert and thus this needs
 	// to be included before any test contents are written
-	if pref.is_test {
+	if pref_.is_test {
 		global_g.write_tests_definitions()
 	}
 
@@ -342,7 +342,7 @@ pub fn gen(files []&ast.File, table &ast.Table, pref &pref.Preferences) (string,
 	util.timing_measure('cgen init')
 	global_g.tests_inited = false
 	global_g.file = files.last()
-	if !pref.no_parallel {
+	if !pref_.no_parallel {
 		util.timing_start('cgen parallel processing')
 		mut pp := pool.new_pool_processor(callback: cgen_process_one_file_cb)
 		pp.set_shared_context(global_g) // TODO: make global_g shared
diff --git a/vlib/v/gen/c/cheaders.v b/vlib/v/gen/c/cheaders.v
index 8fbe7e7888..32798cfd5c 100644
--- a/vlib/v/gen/c/cheaders.v
+++ b/vlib/v/gen/c/cheaders.v
@@ -61,9 +61,9 @@ static inline void __sort_ptr(uintptr_t a[], bool b[], int l) {
 // Inspired from Chris Wellons's work
 // https://nullprogram.com/blog/2017/01/08/
 
-fn c_closure_helpers(pref &pref.Preferences) string {
+fn c_closure_helpers(pref_ &pref.Preferences) string {
 	mut builder := strings.new_builder(2048)
-	if pref.os != .windows {
+	if pref_.os != .windows {
 		builder.writeln('#include <sys/mman.h>')
 	}
 
diff --git a/vlib/v/gen/golang/golang.v b/vlib/v/gen/golang/golang.v
index 8c05af4b37..561ca5382d 100644
--- a/vlib/v/gen/golang/golang.v
+++ b/vlib/v/gen/golang/golang.v
@@ -45,10 +45,10 @@ pub mut:
 	nlines             int
 }
 
-pub fn gen(files []&ast.File, table &ast.Table, out_file string, pref &pref.Preferences) (int, int) {
+pub fn gen(files []&ast.File, table &ast.Table, out_file string, pref_ &pref.Preferences) (int, int) {
 	mut g := Gen{
 		table: table
-		pref: pref
+		pref: pref_
 		// is_debug: is_debug
 		out: strings.new_builder(1000)
 		out_imports: strings.new_builder(200)
diff --git a/vlib/v/gen/js/js.v b/vlib/v/gen/js/js.v
index 036ac3e43e..ef9772934a 100644
--- a/vlib/v/gen/js/js.v
+++ b/vlib/v/gen/js/js.v
@@ -100,11 +100,11 @@ fn (mut g JsGen) write_tests_definitions() {
 	g.definitions.writeln('globalThis.g_test_fails = 0;')
 }
 
-pub fn gen(files []&ast.File, table &ast.Table, pref &pref.Preferences) string {
+pub fn gen(files []&ast.File, table &ast.Table, pref_ &pref.Preferences) string {
 	mut g := &JsGen{
 		definitions: strings.new_builder(100)
 		table: table
-		pref: pref
+		pref: pref_
 		fn_decl: 0
 		empty_line: true
 		doc: 0
@@ -115,7 +115,7 @@ pub fn gen(files []&ast.File, table &ast.Table, pref &pref.Preferences) string {
 	}
 	g.doc = new_jsdoc(g)
 	// TODO: Add '[-no]-jsdoc' flag
-	if pref.is_prod {
+	if g.pref.is_prod {
 		g.enable_doc = false
 		g.is_vlines_enabled = false
 	}
diff --git a/vlib/v/gen/native/gen.v b/vlib/v/gen/native/gen.v
index 55cb156dd0..950b80e341 100644
--- a/vlib/v/gen/native/gen.v
+++ b/vlib/v/gen/native/gen.v
@@ -223,8 +223,8 @@ fn get_backend(arch pref.Arch) !CodeGen {
 	return error('unsupported architecture')
 }
 
-pub fn gen(files []&ast.File, table &ast.Table, out_name string, pref &pref.Preferences) (int, int) {
-	exe_name := if pref.os == .windows && !out_name.ends_with('.exe') {
+pub fn gen(files []&ast.File, table &ast.Table, out_name string, pref_ &pref.Preferences) (int, int) {
+	exe_name := if pref_.os == .windows && !out_name.ends_with('.exe') {
 		out_name + '.exe'
 	} else {
 		out_name
@@ -233,16 +233,16 @@ pub fn gen(files []&ast.File, table &ast.Table, out_name string, pref &pref.Pref
 		table: table
 		sect_header_name_pos: 0
 		out_name: exe_name
-		pref: pref
+		pref: pref_
 		files: files
 		// TODO: workaround, needs to support recursive init
-		code_gen: get_backend(pref.arch) or {
+		code_gen: get_backend(pref_.arch) or {
 			eprintln('No available backend for this configuration. Use `-a arm64` or `-a amd64`.')
 			exit(1)
 		}
 		labels: 0
 		structs: []Struct{len: table.type_symbols.len}
-		eval: eval.new_eval(table, pref)
+		eval: eval.new_eval(table, pref_)
 	}
 	g.code_gen.g = g
 	g.generate_header()
diff --git a/vlib/v/markused/markused.v b/vlib/v/markused/markused.v
index b86c8743af..d4dc95f6dd 100644
--- a/vlib/v/markused/markused.v
+++ b/vlib/v/markused/markused.v
@@ -7,7 +7,7 @@ import v.util
 import v.pref
 
 // mark_used walks the AST, starting at main() and marks all used fns transitively
-pub fn mark_used(mut table ast.Table, pref &pref.Preferences, ast_files []&ast.File) {
+pub fn mark_used(mut table ast.Table, pref_ &pref.Preferences, ast_files []&ast.File) {
 	mut all_fns, all_consts, all_globals := all_fn_const_and_global(ast_files)
 	util.timing_start(@METHOD)
 	defer {
@@ -126,7 +126,7 @@ pub fn mark_used(mut table ast.Table, pref &pref.Preferences, ast_files []&ast.F
 		'v.embed_file.find_index_entry_by_path',
 	]
 
-	if pref.is_bare {
+	if pref_.is_bare {
 		all_fn_root_names << [
 			'strlen',
 			'memcmp',
@@ -137,7 +137,7 @@ pub fn mark_used(mut table ast.Table, pref &pref.Preferences, ast_files []&ast.F
 		]
 	}
 
-	is_noscan_whitelisted := pref.gc_mode in [.boehm_full_opt, .boehm_incr_opt]
+	is_noscan_whitelisted := pref_.gc_mode in [.boehm_full_opt, .boehm_incr_opt]
 
 	for k, mut mfn in all_fns {
 		$if trace_skip_unused_all_fns ? {
@@ -186,7 +186,7 @@ pub fn mark_used(mut table ast.Table, pref &pref.Preferences, ast_files []&ast.F
 			all_fn_root_names << k
 			continue
 		}
-		if pref.is_prof {
+		if pref_.is_prof {
 			if k.starts_with('time.vpc_now') || k.starts_with('v.profile.') {
 				// needed for -profile
 				all_fn_root_names << k
@@ -210,7 +210,7 @@ pub fn mark_used(mut table ast.Table, pref &pref.Preferences, ast_files []&ast.F
 			continue
 		}
 		// testing framework:
-		if pref.is_test {
+		if pref_.is_test {
 			if k.starts_with('test_') || k.contains('.test_') {
 				all_fn_root_names << k
 				continue
@@ -223,7 +223,7 @@ pub fn mark_used(mut table ast.Table, pref &pref.Preferences, ast_files []&ast.F
 		}
 		// public/exported functions can not be skipped,
 		// especially when producing a shared library:
-		if mfn.is_pub && pref.is_shared {
+		if mfn.is_pub && pref_.is_shared {
 			all_fn_root_names << k
 			continue
 		}
@@ -232,19 +232,19 @@ pub fn mark_used(mut table ast.Table, pref &pref.Preferences, ast_files []&ast.F
 			all_fn_root_names << k
 			continue
 		}
-		if pref.prealloc && k.starts_with('prealloc_') {
+		if pref_.prealloc && k.starts_with('prealloc_') {
 			all_fn_root_names << k
 			continue
 		}
 	}
 
 	// handle assertions and testing framework callbacks:
-	if pref.is_debug {
+	if pref_.is_debug {
 		all_fn_root_names << 'panic_debug'
 	}
 	all_fn_root_names << 'panic_option_not_set'
 	all_fn_root_names << 'panic_result_not_set'
-	if pref.is_test {
+	if pref_.is_test {
 		all_fn_root_names << 'main.cb_assertion_ok'
 		all_fn_root_names << 'main.cb_assertion_failed'
 		if benched_tests_sym := table.find_sym('main.BenchedTests') {
@@ -333,7 +333,7 @@ pub fn mark_used(mut table ast.Table, pref &pref.Preferences, ast_files []&ast.F
 	}
 
 	// handle -live main programs:
-	if pref.is_livemain {
+	if pref_.is_livemain {
 		all_fn_root_names << 'v.live.executable.start_reloader'
 		all_fn_root_names << 'v.live.executable.new_live_reload_info'
 	}
@@ -344,7 +344,7 @@ pub fn mark_used(mut table ast.Table, pref &pref.Preferences, ast_files []&ast.F
 		all_fns: all_fns
 		all_consts: all_consts
 		all_globals: all_globals
-		pref: pref
+		pref: pref_
 	}
 	// println( all_fns.keys() )
 	walker.mark_markused_fns() // tagged with `[markused]`
@@ -367,7 +367,7 @@ pub fn mark_used(mut table ast.Table, pref &pref.Preferences, ast_files []&ast.F
 				|| k.starts_with('map_') {
 				walker.fn_decl(mut mfn)
 			}
-			if pref.gc_mode in [.boehm_full_opt, .boehm_incr_opt] {
+			if pref_.gc_mode in [.boehm_full_opt, .boehm_incr_opt] {
 				if k in ['new_map_noscan_key', 'new_map_noscan_value', 'new_map_noscan_key_value',
 					'new_map_init_noscan_key', 'new_map_init_noscan_value',
 					'new_map_init_noscan_key_value'] {
@@ -397,10 +397,10 @@ pub fn mark_used(mut table ast.Table, pref &pref.Preferences, ast_files []&ast.F
 	}
 
 	for kcon, con in all_consts {
-		if pref.is_shared && con.is_pub {
+		if pref_.is_shared && con.is_pub {
 			walker.mark_const_as_used(kcon)
 		}
-		if !pref.is_shared && con.is_pub && con.name.starts_with('main.') {
+		if !pref_.is_shared && con.is_pub && con.name.starts_with('main.') {
 			walker.mark_const_as_used(kcon)
 		}
 	}
diff --git a/vlib/v/parser/parser.v b/vlib/v/parser/parser.v
index 08d700b9d1..06fe6da954 100644
--- a/vlib/v/parser/parser.v
+++ b/vlib/v/parser/parser.v
@@ -126,15 +126,15 @@ pub fn parse_stmt(text string, table &ast.Table, scope &ast.Scope) ast.Stmt {
 	return p.stmt(false)
 }
 
-pub fn parse_comptime(tmpl_path string, text string, table &ast.Table, pref &pref.Preferences, scope &ast.Scope) &ast.File {
+pub fn parse_comptime(tmpl_path string, text string, table &ast.Table, pref_ &pref.Preferences, scope &ast.Scope) &ast.File {
 	$if trace_parse_comptime ? {
 		eprintln('> ${@MOD}.${@FN} text: ${text}')
 	}
 	mut p := Parser{
 		file_name: tmpl_path
-		scanner: scanner.new_scanner(text, .skip_comments, pref)
+		scanner: scanner.new_scanner(text, .skip_comments, pref_)
 		table: table
-		pref: pref
+		pref: pref_
 		scope: scope
 		errors: []errors.Error{}
 		warnings: []errors.Warning{}
@@ -144,15 +144,15 @@ pub fn parse_comptime(tmpl_path string, text string, table &ast.Table, pref &pre
 	return res
 }
 
-pub fn parse_text(text string, path string, table &ast.Table, comments_mode scanner.CommentsMode, pref &pref.Preferences) &ast.File {
+pub fn parse_text(text string, path string, table &ast.Table, comments_mode scanner.CommentsMode, pref_ &pref.Preferences) &ast.File {
 	$if trace_parse_text ? {
 		eprintln('> ${@MOD}.${@FN} comments_mode: ${comments_mode:-20} | path: ${path:-20} | text: ${text}')
 	}
 	mut p := Parser{
-		scanner: scanner.new_scanner(text, comments_mode, pref)
+		scanner: scanner.new_scanner(text, comments_mode, pref_)
 		comments_mode: comments_mode
 		table: table
-		pref: pref
+		pref: pref_
 		scope: &ast.Scope{
 			start_pos: 0
 			parent: table.global_scope
@@ -222,7 +222,7 @@ pub fn (mut p Parser) set_path(path string) {
 	}
 }
 
-pub fn parse_file(path string, table &ast.Table, comments_mode scanner.CommentsMode, pref &pref.Preferences) &ast.File {
+pub fn parse_file(path string, table &ast.Table, comments_mode scanner.CommentsMode, pref_ &pref.Preferences) &ast.File {
 	// Note: when comments_mode == .toplevel_comments,
 	// the parser gives feedback to the scanner about toplevel statements, so that the scanner can skip
 	// all the tricky inner comments. This is needed because we do not have a good general solution
@@ -231,10 +231,10 @@ pub fn parse_file(path string, table &ast.Table, comments_mode scanner.CommentsM
 		eprintln('> ${@MOD}.${@FN} comments_mode: ${comments_mode:-20} | path: ${path}')
 	}
 	mut p := Parser{
-		scanner: scanner.new_scanner_file(path, comments_mode, pref) or { panic(err) }
+		scanner: scanner.new_scanner_file(path, comments_mode, pref_) or { panic(err) }
 		comments_mode: comments_mode
 		table: table
-		pref: pref
+		pref: pref_
 		scope: &ast.Scope{
 			start_pos: 0
 			parent: table.global_scope
@@ -248,7 +248,7 @@ pub fn parse_file(path string, table &ast.Table, comments_mode scanner.CommentsM
 	return res
 }
 
-pub fn parse_vet_file(path string, table_ &ast.Table, pref &pref.Preferences) (&ast.File, []vet.Error) {
+pub fn parse_vet_file(path string, table_ &ast.Table, pref_ &pref.Preferences) (&ast.File, []vet.Error) {
 	$if trace_parse_vet_file ? {
 		eprintln('> ${@MOD}.${@FN} path: ${path}')
 	}
@@ -256,10 +256,10 @@ pub fn parse_vet_file(path string, table_ &ast.Table, pref &pref.Preferences) (&
 		parent: 0
 	}
 	mut p := Parser{
-		scanner: scanner.new_scanner_file(path, .parse_comments, pref) or { panic(err) }
+		scanner: scanner.new_scanner_file(path, .parse_comments, pref_) or { panic(err) }
 		comments_mode: .parse_comments
 		table: table_
-		pref: pref
+		pref: pref_
 		scope: &ast.Scope{
 			start_pos: 0
 			parent: global_scope
@@ -335,12 +335,12 @@ pub fn (mut p Parser) parse() &ast.File {
 	}
 	p.scope.end_pos = p.tok.pos
 
-	mut errors := p.errors.clone()
+	mut errors_ := p.errors.clone()
 	mut warnings := p.warnings.clone()
 	mut notices := p.notices.clone()
 
 	if p.pref.check_only {
-		errors << p.scanner.errors
+		errors_ << p.scanner.errors
 		warnings << p.scanner.warnings
 		notices << p.scanner.notices
 	}
@@ -366,7 +366,7 @@ pub fn (mut p Parser) parse() &ast.File {
 		stmts: stmts
 		scope: p.scope
 		global_scope: p.table.global_scope
-		errors: errors
+		errors: errors_
 		warnings: warnings
 		notices: notices
 		global_labels: p.global_labels
@@ -406,7 +406,7 @@ fn (mut q Queue) run() {
 	}
 }
 */
-pub fn parse_files(paths []string, table &ast.Table, pref &pref.Preferences) []&ast.File {
+pub fn parse_files(paths []string, table &ast.Table, pref_ &pref.Preferences) []&ast.File {
 	mut timers := util.new_timers(should_print: false, label: 'parse_files: ${paths}')
 	$if time_parsing ? {
 		timers.should_print = true
@@ -438,7 +438,7 @@ pub fn parse_files(paths []string, table &ast.Table, pref &pref.Preferences) []&
 		mut files := []&ast.File{cap: paths.len}
 		for path in paths {
 			timers.start('parse_file ${path}')
-			files << parse_file(path, table, .skip_comments, pref)
+			files << parse_file(path, table, .skip_comments, pref_)
 			timers.show('parse_file ${path}')
 		}
 		if codegen_files.len > 0 {
diff --git a/vlib/v/parser/v_parser_test.v b/vlib/v/parser/v_parser_test.v
index 9ebebb9878..46e6b9bbfb 100644
--- a/vlib/v/parser/v_parser_test.v
+++ b/vlib/v/parser/v_parser_test.v
@@ -77,8 +77,8 @@ x := 10
 	table := ast.new_table()
 	vpref := &pref.Preferences{}
 	prog := parse_file(s, table, .skip_comments, vpref)
-	mut checker := checker.new_checker(table, vpref)
-	checker.check(prog)
+	mut checker_ := checker.new_checker(table, vpref)
+	checker_.check(prog)
 	res, _, _, _ := c.gen([prog], table, vpref)
 	println(res)
 }
@@ -105,8 +105,8 @@ fn test_one() {
 		scope: scope
 		global_scope: scope
 	}
-	mut checker := checker.new_checker(table, vpref)
-	checker.check(program)
+	mut checker_ := checker.new_checker(table, vpref)
+	checker_.check(program)
 	mut res, _, _, _ := c.gen([program], table, vpref)
 	res = res.replace('\n', '').trim_space().after('#endif')
 	println(res)
diff --git a/vlib/v/scanner/scanner.v b/vlib/v/scanner/scanner.v
index 5938c9f1d1..e00ca04828 100644
--- a/vlib/v/scanner/scanner.v
+++ b/vlib/v/scanner/scanner.v
@@ -106,19 +106,19 @@ pub enum CommentsMode {
 }
 
 // new scanner from file.
-pub fn new_scanner_file(file_path string, comments_mode CommentsMode, pref &pref.Preferences) !&Scanner {
+pub fn new_scanner_file(file_path string, comments_mode CommentsMode, pref_ &pref.Preferences) !&Scanner {
 	if !os.is_file(file_path) {
 		return error('${file_path} is not a .v file')
 	}
 	raw_text := util.read_file(file_path) or { return err }
 	mut s := &Scanner{
-		pref: pref
+		pref: pref_
 		text: raw_text
 		all_tokens: []token.Token{cap: raw_text.len / 3}
 		is_print_line_on_error: true
 		is_print_colored_error: true
 		is_print_rel_paths_on_error: true
-		is_fmt: pref.is_fmt
+		is_fmt: pref_.is_fmt
 		comments_mode: comments_mode
 		file_path: file_path
 		file_base: os.base(file_path)
@@ -128,15 +128,15 @@ pub fn new_scanner_file(file_path string, comments_mode CommentsMode, pref &pref
 }
 
 // new scanner from string.
-pub fn new_scanner(text string, comments_mode CommentsMode, pref &pref.Preferences) &Scanner {
+pub fn new_scanner(text string, comments_mode CommentsMode, pref_ &pref.Preferences) &Scanner {
 	mut s := &Scanner{
-		pref: pref
+		pref: pref_
 		text: text
 		all_tokens: []token.Token{cap: text.len / 3}
 		is_print_line_on_error: true
 		is_print_colored_error: true
 		is_print_rel_paths_on_error: true
-		is_fmt: pref.is_fmt
+		is_fmt: pref_.is_fmt
 		comments_mode: comments_mode
 		file_path: 'internal_memory'
 		file_base: 'internal_memory'
diff --git a/vlib/v/slow_tests/repl/runner/runner.v b/vlib/v/slow_tests/repl/runner/runner.v
index 5ee7dff747..c7142f4108 100644
--- a/vlib/v/slow_tests/repl/runner/runner.v
+++ b/vlib/v/slow_tests/repl/runner/runner.v
@@ -71,14 +71,14 @@ pub fn run_repl_file(wd string, vexec string, file string) !string {
 		file_expected := '${file}.expected.txt'
 		os.write_file(file_result, result) or { panic(err) }
 		os.write_file(file_expected, output) or { panic(err) }
-		diff := diff_files(file_expected, file_result)
+		diff_ := diff_files(file_expected, file_result)
 		return error('Difference found in REPL file: ${file}
 ====> Expected :
 |${output}|
 ====> Got      :
 |${result}|
 ====> Diff     :
-${diff}
+${diff_}
 		')
 	} else {
 		return file.replace('./', '')
@@ -103,14 +103,14 @@ pub fn run_prod_file(wd string, vexec string, file string) !string {
 	if result != expected_content {
 		file_result := '${file}.result.txt'
 		os.write_file(file_result, result) or { panic(err) }
-		diff := diff_files(file_result, file_expected)
+		diff_ := diff_files(file_result, file_expected)
 		return error('Difference found in test: ${file}
 ====> Got      :
 |${result}|
 ====> Expected :
 |${expected_content}|
 ====> Diff     :
-${diff}
+${diff_}
 		')
 	} else {
 		return 'Prod file ${file} is OK'
diff --git a/vlib/v/tests/cross_assign_test.v b/vlib/v/tests/cross_assign_test.v
index abba8667c6..27ec814654 100644
--- a/vlib/v/tests/cross_assign_test.v
+++ b/vlib/v/tests/cross_assign_test.v
@@ -171,20 +171,20 @@ fn test_cross_assign_of_big_int() {
 
 fn test_cross_assign_of_reserved_name_variable() {
 	mut small := 1
-	mut big := 2
+	mut big_ := 2
 	mut sum := 2
 
-	for big < 4_000_000 {
-		small, big = big, small + big
-		if big % 2 == 0 {
-			sum += big
+	for big_ < 4_000_000 {
+		small, big_ = big_, small + big_
+		if big_ % 2 == 0 {
+			sum += big_
 		}
 	}
 	println(small)
 	assert small == 3524578
 
-	println(big)
-	assert big == 5702887
+	println(big_)
+	assert big_ == 5702887
 
 	println(sum)
 	assert sum == 4613732
diff --git a/vlib/v/tests/fn_type_only_argument_test.v b/vlib/v/tests/fn_type_only_argument_test.v
index 11e4208feb..1d781cc4cf 100644
--- a/vlib/v/tests/fn_type_only_argument_test.v
+++ b/vlib/v/tests/fn_type_only_argument_test.v
@@ -1,8 +1,8 @@
 import time
 
 struct Game {
-	update fn (mut time.Time) = fn (mut time time.Time) {}
-	draw   fn (mut time.Time) = fn (mut time time.Time) {}
+	update fn (mut time.Time) = fn (mut time_ time.Time) {}
+	draw   fn (mut time.Time) = fn (mut time_ time.Time) {}
 mut:
 	time time.Time
 }
diff --git a/vlib/v/tests/modules/submodules/submodules_test.v b/vlib/v/tests/modules/submodules/submodules_test.v
index db5daf3ab3..752321130f 100644
--- a/vlib/v/tests/modules/submodules/submodules_test.v
+++ b/vlib/v/tests/modules/submodules/submodules_test.v
@@ -9,13 +9,13 @@ fn test_main() {
 	}
 	assert 'main' == main.a
 
-	test := test.Test{
+	test_ := test.Test{
 		a: 'test'
 	}
-	assert 'test' == test.a
+	assert 'test' == test_.a
 
-	test2 := test2.Test2{
+	test2_ := test2.Test2{
 		a: 'test2'
 	}
-	assert 'test2' == test2.a
+	assert 'test2' == test2_.a
 }
diff --git a/vlib/v/tests/websocket_logger_interface_should_compile_test.v b/vlib/v/tests/websocket_logger_interface_should_compile_test.v
index 39f63888b7..8ae90654eb 100644
--- a/vlib/v/tests/websocket_logger_interface_should_compile_test.v
+++ b/vlib/v/tests/websocket_logger_interface_should_compile_test.v
@@ -42,14 +42,14 @@ fn server() ! {
 		return true
 	})!
 
-	s.on_message(fn (mut ws ws.Client, msg &RawMessage) ! {
+	s.on_message(fn (mut ws_ ws.Client, msg &RawMessage) ! {
 		mut transport := WsTransport{}
 		mut ws_client := new_ws_client(transport)!
 		_ := ws_client
 	})
 
-	s.on_close(fn (mut ws ws.Client, code int, reason string) ! {
-		println('client (${ws.id}) closed connection')
+	s.on_close(fn (mut ws_ ws.Client, code int, reason string) ! {
+		println('client (${ws_.id}) closed connection')
 	})
 
 	s.listen() or { println('error on server listen: ${err}') }
diff --git a/vlib/v/transformer/transformer.v b/vlib/v/transformer/transformer.v
index 3574bcaab5..c3ab086843 100644
--- a/vlib/v/transformer/transformer.v
+++ b/vlib/v/transformer/transformer.v
@@ -13,9 +13,9 @@ mut:
 	is_assert bool
 }
 
-pub fn new_transformer(pref &pref.Preferences) &Transformer {
+pub fn new_transformer(pref_ &pref.Preferences) &Transformer {
 	return &Transformer{
-		pref: pref
+		pref: pref_
 		index: &IndexState{
 			saved_key_vals: [][]KeyVal{cap: 1000}
 			saved_disabled: []bool{cap: 1000}
@@ -23,8 +23,8 @@ pub fn new_transformer(pref &pref.Preferences) &Transformer {
 	}
 }
 
-pub fn new_transformer_with_table(table &ast.Table, pref &pref.Preferences) &Transformer {
-	mut transformer := new_transformer(pref)
+pub fn new_transformer_with_table(table &ast.Table, pref_ &pref.Preferences) &Transformer {
+	mut transformer := new_transformer(pref_)
 	transformer.table = table
 	return transformer
 }
diff --git a/vlib/v/util/module.v b/vlib/v/util/module.v
index 354418031f..07521ff1d0 100644
--- a/vlib/v/util/module.v
+++ b/vlib/v/util/module.v
@@ -16,22 +16,22 @@ fn trace_qualify(callfn string, mod string, file_path string, kind_res string, r
 // 2022-01-30 TODO: this seems to always just return `mod` itself, for modules inside the V main folder.
 // 2022-01-30 It does also return `mod` itself, for stuff installed in ~/.vmodules like `vls` but for
 // 2022-01-30 other reasons (see res 2 below).
-pub fn qualify_import(pref &pref.Preferences, mod string, file_path string) string {
+pub fn qualify_import(pref_ &pref.Preferences, mod string, file_path string) string {
 	// comments are from workdir: /v/vls
-	mut mod_paths := pref.lookup_path.clone()
+	mut mod_paths := pref_.lookup_path.clone()
 	mod_paths << os.vmodules_paths()
 	mod_path := mod.replace('.', os.path_separator)
 	for search_path in mod_paths {
 		try_path := os.join_path_single(search_path, mod_path)
 		if os.is_dir(try_path) {
-			if m1 := mod_path_to_full_name(pref, mod, try_path) {
+			if m1 := mod_path_to_full_name(pref_, mod, try_path) {
 				trace_qualify(@FN, mod, file_path, 'import_res 1', m1, try_path)
 				// >  qualify_import: term | file_path: /v/vls/server/diagnostics.v | => import_res 1: term  ; /v/cleanv/vlib/term
 				return m1
 			}
 		}
 	}
-	if m1 := mod_path_to_full_name(pref, mod, file_path) {
+	if m1 := mod_path_to_full_name(pref_, mod, file_path) {
 		trace_qualify(@FN, mod, file_path, 'import_res 2', m1, file_path)
 		// >  qualify_module: analyzer           | file_path: /v/vls/analyzer/store.v  | =>   module_res 2: analyzer           ; clean_file_path - getwd == mod
 		// >  qualify_import: analyzer.depgraph  | file_path: /v/vls/analyzer/store.v  | =>   import_res 2: analyzer.depgraph  ; /v/vls/analyzer/store.v
@@ -51,7 +51,7 @@ pub fn qualify_import(pref &pref.Preferences, mod string, file_path string) stri
 // 2022-01-30 qualify_module - used by V's parser to find the full module name
 // 2022-01-30 i.e. when parsing `module textscanner`, inside vlib/strings/textscanner/textscanner.v
 // 2022-01-30 it will return `strings.textscanner`
-pub fn qualify_module(pref &pref.Preferences, mod string, file_path string) string {
+pub fn qualify_module(pref_ &pref.Preferences, mod string, file_path string) string {
 	if mod == 'main' {
 		trace_qualify(@FN, mod, file_path, 'module_res 1', mod, 'main')
 		return mod
@@ -68,7 +68,7 @@ pub fn qualify_module(pref &pref.Preferences, mod string, file_path string) stri
 		trace_qualify(@FN, mod, file_path, 'module_res 2', mod, 'clean_file_path - getwd == mod, clean_file_path: ${clean_file_path}')
 		return mod
 	}
-	if m1 := mod_path_to_full_name(pref, mod, clean_file_path) {
+	if m1 := mod_path_to_full_name(pref_, mod, clean_file_path) {
 		trace_qualify(@FN, mod, file_path, 'module_res 3', m1, 'm1 == f(${clean_file_path})')
 		// >  qualify_module: net  | file_path: /v/cleanv/vlib/net/util.v     | =>   module_res 3: net     ; m1 == f(/v/cleanv/vlib/net)
 		// >  qualify_module: term | file_path: /v/cleanv/vlib/term/control.v | =>   module_res 3: term    ; m1 == f(/v/cleanv/vlib/term)
@@ -96,11 +96,11 @@ pub fn qualify_module(pref &pref.Preferences, mod string, file_path string) stri
 // 2022-01-30 just on windows, because while `vlib\v\checker\tests\modules\deprecated_module` works,
 // 2022-01-30 it leads to path differences, and the / version on windows triggers a module lookip bug,
 // 2022-01-30 leading to completely different errors)
-fn mod_path_to_full_name(pref &pref.Preferences, mod string, path string) !string {
+fn mod_path_to_full_name(pref_ &pref.Preferences, mod string, path string) !string {
 	// TODO: explore using `pref.lookup_path` & `os.vmodules_paths()`
 	// absolute paths instead of 'vlib' & '.vmodules'
 	mut vmod_folders := ['vlib', '.vmodules', 'modules']
-	bases := pref.lookup_path.map(os.base(it))
+	bases := pref_.lookup_path.map(os.base(it))
 	for base in bases {
 		if base !in vmod_folders {
 			vmod_folders << base
@@ -157,8 +157,8 @@ fn mod_path_to_full_name(pref &pref.Preferences, mod string, path string) !strin
 			}
 		}
 	}
-	if os.is_abs_path(pref.path) && os.is_abs_path(path) && os.is_dir(path) { // && path.contains(mod )
-		rel_mod_path := path.replace(pref.path.all_before_last(os.path_separator) +
+	if os.is_abs_path(pref_.path) && os.is_abs_path(path) && os.is_dir(path) { // && path.contains(mod )
+		rel_mod_path := path.replace(pref_.path.all_before_last(os.path_separator) +
 			os.path_separator, '')
 		if rel_mod_path != path {
 			full_mod_name := rel_mod_path.replace(os.path_separator, '.')