added validation of paths option

src/compiler/diagnosticMessages.json

@@ -2292,7 +2292,14 @@
         "category": "Error",
         "code": 5062
     },
-
+    "Substututions for patterns '{0}' should be an array.": {
+        "category": "Error",
+        "code": 5063
+    },
+    "Substitution '{0}' for pattern '{1}' has incorrect type, expected 'string', got '{2}'.": {
+        "category": "Error",
+        "code": 5064
+    },
     "Concatenate and emit output to single file.": {
         "category": "Message",
         "code": 6001

src/compiler/program.ts

@@ -1985,11 +1985,22 @@ namespace ts {
                     if (!hasZeroOrOneAsteriskCharacter(key)) {
                         programDiagnostics.add(createCompilerDiagnostic(Diagnostics.Pattern_0_can_have_at_most_one_Asterisk_character, key));
                     }
-                    for (const subst of options.paths[key]) {
-                        if (!hasZeroOrOneAsteriskCharacter(subst)) {
-                            programDiagnostics.add(createCompilerDiagnostic(Diagnostics.Substitution_0_in_pattern_1_in_can_have_at_most_one_Asterisk_character, subst, key));
+                    if (isArray(options.paths[key])) {
+                        for (const subst of options.paths[key]) {
+                            const typeOfSubst = typeof subst;
+                            if (typeOfSubst === "string") {
+                                if (!hasZeroOrOneAsteriskCharacter(subst)) {
+                                    programDiagnostics.add(createCompilerDiagnostic(Diagnostics.Substitution_0_in_pattern_1_in_can_have_at_most_one_Asterisk_character, subst, key));
+                                }
+                            }
+                            else {
+                                programDiagnostics.add(createCompilerDiagnostic(Diagnostics.Substitution_0_for_pattern_1_has_incorrect_type_expected_string_got_2, subst, key, typeOfSubst));
+                            }
                         }
                     }
+                    else {
+                        programDiagnostics.add(createCompilerDiagnostic(Diagnostics.Substututions_for_patterns_0_should_be_an_array, key));
+                    }
                 }
             }
 

tests/baselines/reference/pathsValidation1.errors.txt

@@ -0,0 +1,6 @@
+error TS5063: Substututions for patterns '*' should be an array.
+
+
+!!! error TS5063: Substututions for patterns '*' should be an array.
+==== tests/cases/compiler/a.ts (0 errors) ====
+    let x = 1;

tests/baselines/reference/pathsValidation1.js

@@ -0,0 +1,5 @@
+//// [a.ts]
+let x = 1;
+
+//// [a.js]
+var x = 1;

tests/baselines/reference/pathsValidation2.errors.txt

@@ -0,0 +1,6 @@
+error TS5064: Substitution '1' for pattern '*' has incorrect type, expected 'string', got 'number'.
+
+
+!!! error TS5064: Substitution '1' for pattern '*' has incorrect type, expected 'string', got 'number'.
+==== tests/cases/compiler/a.ts (0 errors) ====
+    let x = 1;

tests/baselines/reference/pathsValidation2.js

@@ -0,0 +1,5 @@
+//// [a.ts]
+let x = 1;
+
+//// [a.js]
+var x = 1;

tests/cases/compiler/pathsValidation1.ts

@@ -0,0 +1,11 @@
+// @filename: tsconfig.json
+{
+    "compilerOptions": {
+        "baseUrl": ".",
+        "paths": {
+            "*": "*"
+        }
+    }
+}
+// @filename: a.ts
+let x = 1;

tests/cases/compiler/pathsValidation2.ts

@@ -0,0 +1,11 @@
+// @filename: tsconfig.json
+{
+    "compilerOptions": {
+        "baseUrl": ".",
+        "paths": {
+            "*": [1]
+        }
+    }
+}
+// @filename: a.ts
+let x = 1;