From 075a8e5ccb8a3287ce546aca8e0428bb4c9d79ec Mon Sep 17 00:00:00 2001
From: joe-conigliaro <joe-conigliaro@users.noreply.github.com>
Date: Mon, 16 Sep 2019 03:07:12 +1000
Subject: [PATCH] compiler: improve typo detection

---
 compiler/fn.v             |  8 ++++----
 compiler/table.v          | 27 +++++++++++++++++++--------
 vlib/strings/similarity.v | 19 +++++++++----------
 3 files changed, 32 insertions(+), 22 deletions(-)

diff --git a/compiler/fn.v b/compiler/fn.v
index d789530282..f3c0090fa0 100644
--- a/compiler/fn.v
+++ b/compiler/fn.v
@@ -1015,12 +1015,12 @@ fn (f &Fn) find_misspelled_local_var(name string, min_match f32) string {
 	mut closest := f32(0)
 	mut closest_var := ''
 	for var in f.local_vars {
-		n := '${f.mod}.$var.name'
-		if var.name == '' || !name.starts_with(f.mod) || (n.len - name.len > 3 || name.len - n.len > 3) { continue }
-		p := strings.dice_coefficient(name, n)
+		n := name.all_after('.')
+		if var.name == '' || (n.len - var.name.len > 2 || var.name.len - n.len > 2) { continue }
+		p := strings.dice_coefficient(var.name, n)
 		if p > closest {
 			closest = p
-			closest_var = n
+			closest_var = var.name
 		}
 	}
 	return if closest >= min_match { closest_var } else { '' }
diff --git a/compiler/table.v b/compiler/table.v
index 2211f10324..0ed7e39ca7 100644
--- a/compiler/table.v
+++ b/compiler/table.v
@@ -856,11 +856,11 @@ fn (t &Type) contains_field_type(typ string) bool {
 fn (table &Table) identify_typo(name string, current_fn &Fn, fit &FileImportTable) string {
 	// dont check if so short
 	if name.len < 2 { return '' }
-	min_match := 0.8 // for dice coefficient between 0.0 - 1.0
+	min_match := 0.50 // for dice coefficient between 0.0 - 1.0
 	name_orig := name.replace('__', '.').replace('_dot_', '.')
 	mut output := ''
 	// check functions
-	mut n := table.find_misspelled_fn(name_orig, min_match)
+	mut n := table.find_misspelled_fn(name, fit, min_match)
 	if n != '' {
 		output += '\n  * function: `$n`'
 	}
@@ -878,16 +878,27 @@ fn (table &Table) identify_typo(name string, current_fn &Fn, fit &FileImportTabl
 }
 
 // find function with closest name to `name`
-fn (table &Table) find_misspelled_fn(name string, min_match f32) string {
+fn (table &Table) find_misspelled_fn(name string, fit &FileImportTable, min_match f32) string {
 	mut closest := f32(0)
 	mut closest_fn := ''
+	is_main_fn := name.starts_with('main__')
+	n1 := if is_main_fn { name.right(6) } else { name }
 	for _, f in table.fns {
-		n := '${f.mod}.$f.name'
-		if !name.starts_with(f.mod) || (n.len - name.len > 3 || name.len - n.len > 3) { continue }
-		p := strings.dice_coefficient(name, n)
+		if n1.len - f.name.len > 2 || f.name.len - n1.len > 2 { continue }
+		if !(f.mod in ['', 'main', 'builtin']) {
+			mut mod_imported := false
+			for _, m in fit.imports {
+				if f.mod == m {
+					mod_imported = true
+					break
+				}
+			}
+			if !mod_imported { continue }
+		}
+		p := strings.dice_coefficient(n1, f.name)
 		if p > closest {
 			closest = p
-			closest_fn = n
+			closest_fn = f.name
 		}
 	}
 	return if closest >= min_match { closest_fn } else { '' }
@@ -899,7 +910,7 @@ fn (table &Table) find_misspelled_imported_mod(name string, fit &FileImportTable
 	mut closest_mod := ''
 	for alias, mod in fit.imports {
 		n := '${fit.module_name}.$alias'
-		if !name.starts_with(fit.module_name) || (n.len - name.len > 3 || name.len - n.len > 3) { continue }
+		if !name.starts_with(fit.module_name) || (n.len - name.len > 2 || name.len - n.len > 2) { continue }
 		p := strings.dice_coefficient(name, n)
 		if p > closest {
 			closest = p
diff --git a/vlib/strings/similarity.v b/vlib/strings/similarity.v
index dfa5596665..7ae64fa35c 100644
--- a/vlib/strings/similarity.v
+++ b/vlib/strings/similarity.v
@@ -40,22 +40,21 @@ pub fn dice_coefficient(s1, s2 string) f32 {
 	if s1.len == 0 || s2.len == 0 { return 0.0 }
 	if s1 == s2 { return 1.0 }
 	if s1.len < 2 || s2.len < 2 { return 0.0 }
+	a := if s1.len > s2.len { s1 } else { s2 }
+	b := if a == s1 { s2 } else { s1 }
 	mut first_bigrams := map[string]int
-	for i := 0; i < s1.len-1; i++ {
-		a := s1[i]
-		b := s1[i+1]
-		bigram := (a+b).str()
+	for i := 0; i < a.len-1; i++ {
+		bigram := a.substr(i, i+2)
 		first_bigrams[bigram] = if bigram in first_bigrams { first_bigrams[bigram]+1 } else { 1 }
 	}
 	mut intersection_size := 0
-	for i := 0; i < s2.len-1; i++ {
-		a := s2[i]
-		b := s2[i+1]
-		bigram := (a+b).str()
-		count := if bigram in first_bigrams { first_bigrams[bigram] } else { 0 }
+	for i := 0; i < b.len-1; i++ {
+		bigram := b.substr(i, i+2)
+		count := if bigram in first_bigrams { first_bigrams[bigram] } else { 0 } 
 		if count > 0 {
+			first_bigrams[bigram] = count - 1
 			intersection_size++
 		}
 	}
-	return (2.0 * intersection_size) / (f32(s1.len) + f32(s2.len) - 2)
+	return (2.0 * intersection_size) / (f32(a.len) + f32(b.len) - 2)
 }