compiler: improve module import error messages

compiler/main.v

@@ -216,21 +216,28 @@ fn (v mut V) add_parser(parser Parser) {
 	   v.parsers << parser
 }
 
-// find existing parser or create new one. returns v.parsers index
-fn (v mut V) parse(file string, pass Pass) int {
-	//println('parse($file, $pass)')
+fn (v &V) get_file_parser_index(file string) ?int {
 	for i, p in v.parsers {
 		if os.realpath(p.file_path) == os.realpath(file) {
-			v.parsers[i].parse(pass)
-			//if v.parsers[i].pref.autofree {	v.parsers[i].scanner.text.free()	free(v.parsers[i].scanner)	}
 			return i
 		}	
 	}
-	mut p := v.new_parser_from_file(file)
-	p.parse(pass)
-	//if p.pref.autofree {		p.scanner.text.free()		free(p.scanner)	}
-	v.add_parser(p)
-	return v.parsers.len-1
+	return error('parser for "$file" not found')
+}
+
+// find existing parser or create new one. returns v.parsers index
+fn (v mut V) parse(file string, pass Pass) int {
+	//println('parse($file, $pass)')
+	pidx := v.get_file_parser_index(file) or {
+		mut p := v.new_parser_from_file(file)
+		p.parse(pass)
+		//if p.pref.autofree {		p.scanner.text.free()		free(p.scanner)	}
+		v.add_parser(p)
+		return v.parsers.len-1
+	}
+	v.parsers[pidx].parse(pass)
+	//if v.parsers[i].pref.autofree {	v.parsers[i].scanner.text.free()	free(v.parsers[i].scanner)	}
+	return pidx
 }
 
 
@@ -622,7 +629,8 @@ fn (v mut V) add_v_files_to_compile() {
 		// 	continue
 		// }
 		// standard module
-		vfiles := v.v_files_from_dir(v.find_module_path(mod))
+		mod_path := v.find_module_path(mod) or { verror(err) break }
+		vfiles := v.v_files_from_dir(mod_path)
 		for file in vfiles {
 			v.files << file
 		}
@@ -694,10 +702,15 @@ fn (v mut V) parse_lib_imports() {
 	for _, fit in v.table.file_imports {
 		if fit.file_path in done_fits { continue }
 		for _, mod in fit.imports {
-			import_path := v.find_module_path(mod)
+			import_path := v.find_module_path(mod) or {
+				pidx := v.get_file_parser_index(fit.file_path) or { verror(err) break }
+				v.parsers[pidx].error_with_token_index('cannot import module "$mod" (not found)', fit.get_import_tok_idx(mod))
+				break
+			}
 			vfiles := v.v_files_from_dir(import_path)
 			if vfiles.len == 0 {
-				verror('cannot import module $mod (no .v files in "$import_path")')
+				pidx := v.get_file_parser_index(fit.file_path) or { verror(err) break }
+				v.parsers[pidx].error_with_token_index('cannot import module "$mod" (no .v files in "$import_path")', fit.get_import_tok_idx(mod))
 			}
 			// Add all imports referenced by these libs
 			for file in vfiles {
@@ -706,7 +719,7 @@ fn (v mut V) parse_lib_imports() {
 				done_imports << file
 				p_mod := v.parsers[pid].import_table.module_name
 				if p_mod != mod {
-					verror('bad module name: $file was imported as `$mod` but it is defined as module `$p_mod`')
+					v.parsers[pid].error_with_token_index('bad module definition: $fit.file_path imports module "$mod" but $file is defined as module `$p_mod`', 1)
 				}
 			}
 		}

compiler/modules.v

@@ -42,7 +42,7 @@ fn (v &V) module_path(mod string) string {
 // 'strings' => 'VROOT/vlib/strings'
 // 'installed_mod' => '~/.vmodules/installed_mod'
 // 'local_mod' => '/path/to/current/dir/local_mod'
-fn (v &V) find_module_path(mod string) string {
+fn (v &V) find_module_path(mod string) ?string {
 	mod_path := v.module_path(mod)
 	// First check for local modules in the same directory
 	mut import_path := os.getwd() + '${os.PathSeparator}$mod_path'
@@ -55,7 +55,7 @@ fn (v &V) find_module_path(mod string) string {
 	if !os.dir_exists(import_path) {
 		import_path = '$v_modules_path${os.PathSeparator}$mod_path'
 		if !os.dir_exists(import_path){
-			verror('module "$mod" not found')
+			return error('module "$mod" not found')
 		}
 	}
 	return import_path

compiler/parser.v

@@ -437,6 +437,7 @@ fn (p mut Parser) import_statement() {
 	if p.peek() == .number { // && p.scanner.text[p.scanner.pos + 1] == `.` {
 		p.error('bad import format. module/submodule names cannot begin with a number')
 	}
+	import_tok_idx := p.token_idx-1
 	mut mod := p.check_name().trim_space()
 	mut mod_alias := mod
 	// submodule support
@@ -457,7 +458,7 @@ fn (p mut Parser) import_statement() {
 		mod_alias = p.check_name()
 	}
 	// add import to file scope import table
-	p.import_table.register_alias(mod_alias, mod)
+	p.import_table.register_alias(mod_alias, mod, import_tok_idx)
 	// Make sure there are no duplicate imports
 	if mod in p.table.imports {
 		return

compiler/table.v

@@ -53,10 +53,11 @@ mut:
 // Holds import information scoped to the parsed file
 struct FileImportTable {
 mut:
-	module_name  string
-	file_path    string
-	imports      map[string]string // alias => module
-	used_imports []string          // alias
+	module_name    string
+	file_path      string
+	imports        map[string]string // alias => module
+	used_imports   []string          // alias
+	import_tok_idx map[string]int    // module => idx
 }
 
 enum AccessMod {
@@ -896,11 +897,11 @@ fn (fit &FileImportTable) known_import(mod string) bool {
 	return mod in fit.imports || fit.is_aliased(mod)
 }
 
-fn (fit mut FileImportTable) register_import(mod string) {
-	fit.register_alias(mod, mod)
+fn (fit mut FileImportTable) register_import(mod string, tok_idx int) {
+	fit.register_alias(mod, mod, tok_idx)
 }
 
-fn (fit mut FileImportTable) register_alias(alias string, mod string) {
+fn (fit mut FileImportTable) register_alias(alias string, mod string, tok_idx int) {
 	// NOTE: come back here
 	// if alias in fit.imports && fit.imports[alias] == mod {}
 	if alias in fit.imports && fit.imports[alias] != mod {
@@ -919,6 +920,11 @@ fn (fit mut FileImportTable) register_alias(alias string, mod string) {
 		}
 	}
 	fit.imports[alias] = mod
+	fit.import_tok_idx[mod] = tok_idx
+}
+
+fn (fit &FileImportTable) get_import_tok_idx(mod string) int {
+	return fit.import_tok_idx[mod]
 }
 
 fn (fit &FileImportTable) known_alias(alias string) bool {